ICSI-ET Cycle Outcome Based on Endometrial Blood Flow Pattern- A Prospective Observational Study
Shabana Babu *1, Siri Vummaneni 2, Krithika Muthusamy 3
*Correspondence to: Dr. Shabana Babu MBBS, MS, DNB, OBGYN. Department of Obstetrics and Gynaecology. Tamil Nadu.
© 2024 Dr. Shabana Babu. This is an open access article distributed under the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.
Received: 20 August 2024
Published: 10 September 2024
Abbreviations
|
IVF E2 P |
In Vitro Fertilization Estrogen Progesterone |
|
WOI |
Window of Implantation |
|
ART |
Assisted Reproductive Technology |
|
ICSI |
Intracytoplasmic Sperm Injection |
|
FET |
Frozen-thawed Embryo Transfers |
|
USG COH US |
Ultrasonography Controlled ovarian hyperstimulation Ultrasound |
|
CDC |
Centers for Disease Control |
|
PGT-A |
Pre-implantation genetic screening |
|
2D-PD |
2-Dimensional Power Doppler |
|
BMI |
Body Mass Index |
|
FSH |
Follicle Stimulating Hormone |
|
LH |
Luteinizing Hormone |
|
PI |
Pulsatility Index |
|
NC |
Natural Cycle |
|
HRT |
Hormone Replacement Therapy |
|
HCG GnRH OR |
Human Chorionic Gonadotrophin Gonadotrophin releasing hormone Oocyte retrieval |
|
STC |
Stimulated Cycles |
|
PCOS |
Polycystic Ovarian Syndrome |
Introduction
Infertility is characterised as a condition where a clinical pregnancy cannot be established after 12 months of regular, unprotected sexual activity or where a person's ability to reproduce, either alone or with a partner, is impaired. (1) More than 186 million people worldwide have infertility, with most of them living in developing nations. (2) While the age of the mother at conception is the strongest negative predictor of fertility (3), other factors, such as lifestyle choices and environmental factors, are thought to play an increasing influence. The success rates of IVF ongoing pregnancy per cycle varies between 8.6 and 46.2%. (4)
Estrogen and progesterone influence the preparation of endometrium for implantation; however, only about half of all produced embryos will implant and lead to a successful ongoing pregnancy. (5) The window of implantation is limited to a receptive window between 7- and 10-days following ovulation. (6) Numerous variables, including uterine receptivity, endometrial thickness (7,8) and endometrial texture (9), have been identified as being essential to conception.
Receptivity refers to the endometrium's capacity to support normal implantation, and optimal receptivity results in normal implantation procedures that provide the foundation for a healthy pregnancy.The mid-luteal phase is when the majority of women reach their normal receptivity, and this is completely the result of the sequential effects of the steroid hormones E2 and P. The down-regulation of oestrogen receptor-a, appears to be one crucial event that determines receptivity (10). "That stage of endometrial maturation during which the tropho-ectoderm of the blastocyst is capable of adhering to the endometrial epithelial cells and subsequently advancing to invade the endometrial stroma and vasculature," is known as endometrial receptivity. (11)
Fecundity begins to decline gradually after age 32 and then rapidly beyond age 38. (12) To top it, there are various complex synchronised physiological and biochemical interactions that occur between the blastocyst and the endometrium which ultimately lead to embryo implantation. (13) The endometrium must be in a receptive state for this to happen. The "window of implantation" (WOI) in humans is a specially designated time frame that lasts for 2-4 days in the mid-luteal phase. (14). Assisted reproductive technologies (ART) is a boon for such patients to plan a successful parenthood.
One of the techniques of ART is Intracytoplasmic sperm injection (ICSI). In ICSI, a single sperm is selected to be injected into an egg rather than multiple sperms which increases the chances of fertilization. In vitro fertilisation (IVF)-intracytoplasmic sperm injection (ICSI) cycles often result in an excess of embryos that need to be stored and transferred. This method is known as frozen-thawed (FT) embryo transfer. The number of FT embryo transfer cycles has steadily increased in recent years as a result of advances in laboratory conditions and restrictions on the number of embryos that can be transferred. Transferring a single embryo and freezing all surplus embryos is another recommended method for preventing multiple pregnancies during IVF cycles. (15)
When compared to repeated fresh embryo transfers, FT embryo transfer boosts the cumulative pregnancy rate, lowers the cost, is simple to perform, and can be performed in a shorter amount of time (16).
Success rates for frozen embryo transfer cycles depend on a variety of variables, including the patient's age, the quality of the embryos before freezing, the number of embryos transferred, the freezing and thawing protocol, and endometrial preparation. The most crucial stage of assisted reproductive techniques (ART) is embryo implantation, which depends on three key factors: embryo quality, endometrial receptivity, and appropriate endometrial growth and embryonic development timing. (17).
Study Methodology
It was a prospective observational study where 30 women undergoing frozen embryo transfer (FET) cycle in our infertility center from January 2022 to June 2022 were recruited. The study was approved by the Ethical Committee of the hospital, and all patients consented to participate in the study.
Inclusion Criteria
Exclusion criteria
All patients in the inclusion criteria undergoing Frozen Embryo Transfer will be subjected to basal transvaginal ultrasound on day 2 to assess the endometrial thickness and adnexa. Hormone replacement therapy will be started according to the institutional protocol (Inj. Lupride 10 units subcutaneously+ estradiol valerate 2mg orally thrice a day). Patients will be reassessed serially till endometrial thickness reaches 7 mm and above with maximum estrogen support( estradiol valerate 12mg orally + 6 mg vaginally). Endometrial thickness and doppler color flow pattern will be assessed before starting progestrone support and patients are categorised into zone 1-4 according to Applebaum score.
All scans were done on GE voluson S8 between 9am -11am. A B-Mode exploration of both uterus and ovaries was initially done. Then the endometrium was assessed in the longitudinal section for its thickness, which was measured from outside to outside at its widest point. Using Power Doppler, the endometrial blood flow distribution pattern was determined by demonstrating color signals.
For the zones of endometrial blood flow, we followed the definition by Applebaum, summarized as follows:
Serum Progestrone value will also be taken. Embryo transfer is done depending upon the day of embryo( Day 4/5).Serum Beta HCG value is taken on day 15 after Embryo transfer. A value of 100 or more is taken as a positive pregnancy. Patients are followed up till 6 weeks and categorised into primary and secondary outcome.
The variable Age (Years) was not normally distributed in the 3 subgroups of the variable CF Zone. Thus, non-parametric tests (Kruskal Wallis Test) were used to make group comparisons.
The mean (SD) of Age (Years) in the CF Zone: Zone 1 group was 31.14 (5.58). The mean (SD) of Age (Years) in the CF Zone: Zone 2 group was 32.71 (6.52). The mean (SD) of Age (Years) in the CF Zone: Zone 3 group was 33.62 (7.63). The median (IQR) of Age (Years) in the CF Zone: Zone 1 group was 30 (28-35.5). The median (IQR) of Age (Years) in the CF Zone: Zone 2 group was 29 (28-37.5). The median (IQR) of Age (Years) in the CF Zone: Zone 3 group was 33 (28-37.25). The Age (Years) in the CF Zone: Zone 1 ranged from 23 - 38. The Age (Years) in the CF Zone: Zone 2 ranged from 26 - 43. The Age (Years) in the CF Zone: Zone 3 ranged from 21 - 48.
There was no significant difference between the groups in terms of Age (Years) (χ2 = 0.256, p = 0.880).
Strength of Association (Kendall's Tau) = 0.07 (Little/No Association)
The Box-and-Whisker plot below depicts the distribution of Age (Years) in the 3 groups. The middle horizontal line represents the median Age (Years), the upper and lower bounds of the box represent the 75th and the 25th centile of Age (Years) respectively, and the upper and lower extent of the whiskers represent the Tukey limits for Age (Years) in each of the groups.
Fisher's exact test was used to explore the association between 'CF Zone' and 'Age' as more than 20% of the total number of cells had an expected count of less than 5.
There was no significant difference between the various groups in terms of distribution of Age (χ2 = 2.384, p = 0.826).
Strength of association between the two variables (Cramer's V) = 0.2 (Low Association)
Strength of association between the two variables (Bias Corrected Cramer's V) = 0 (Little/No Association)
57.1% of the participants in the group [CF Zone: Zone 1] had [Age: 21-30 Years]. 42.9% of the participants in the group [CF Zone: Zone 1] had [Age: 31-40 Years]. 0.0% of the participants in the group [CF Zone: Zone 1] had [Age: >40 Years]. 57.1% of the participants in the group [CF Zone: Zone 2] had [Age: 21-30 Years]. 28.6% of the participants in the group [CF Zone: Zone 2] had [Age: 31-40 Years]. 14.3% of the participants in the group [CF Zone: Zone 2] had [Age: >40 Years]. 43.8% of the participants in the group [CF Zone: Zone 3] had [Age: 21-30 Years]. 31.2% of the participants in the group [CF Zone: Zone 3] had [Age: 31-40 Years]. 25.0% of the participants in the group [CF Zone: Zone 3] had [Age: >40 Years].
The variable Weight (Kg) was not normally distributed in the 3 subgroups of the variable CF Zone. Thus, non-parametric tests (Kruskal Wallis Test) were used to make group comparisons.
The mean (SD) of Weight (Kg) in the CF Zone: Zone 1 group was 73.99 (16.26). The mean (SD) of Weight (Kg) in the CF Zone: Zone 2 group was 61.57 (19.62). The mean (SD) of Weight (Kg) in the CF Zone: Zone 3 group was 62.46 (9.71). The median (IQR) of Weight (Kg) in the CF Zone: Zone 1 group was 70.8 (60.5-84.6). The median (IQR) of Weight (Kg) in the CF Zone: Zone 2 group was 52 (50-71). The median (IQR) of Weight (Kg) in the CF Zone: Zone 3 group was 60.3 (53.12-70.07). The Weight (Kg) in the CF Zone: Zone 1 ranged from 57.2 - 99.7. The Weight (Kg) in the CF Zone: Zone 2 ranged from 40 - 97. The Weight (Kg) in the CF Zone: Zone 3 ranged from 51 - 78.
There was no significant difference between the groups in terms of Weight (Kg) (χ2 = 3.890, p = 0.143).
Strength of Association (Kendall's Tau) = 0.15 (Small Effect Size)
The Box-and-Whisker plot below depicts the distribution of Weight (Kg) in the 3 groups. The middle horizontal line represents the median Weight (Kg), the upper and lower bounds of the box represent the 75th and the 25th centile of Weight (Kg) respectively, and the upper and lower extent of the whiskers represent the Tukey limits for Weight (Kg) in each of the groups.
The variable BMI (Kg/m²) was not normally distributed in the 3 subgroups of the variable CF Zone. Thus, non-parametric tests (Kruskal Wallis Test) were used to make group comparisons.
The mean (SD) of BMI (Kg/m²) in the CF Zone: Zone 1 group was 30.03 (5.00). The mean (SD) of BMI (Kg/m²) in the CF Zone: Zone 2 group was 26.43 (8.42). The mean (SD) of BMI (Kg/m²) in the CF Zone: Zone 3 group was 26.85 (4.51). The median (IQR) of BMI (Kg/m²) in the CF Zone: Zone 1 group was 31.1 (26.3-33.45). The median (IQR) of BMI (Kg/m²) in the CF Zone: Zone 2 group was 23 (21-30). The median (IQR) of BMI (Kg/m²) in the CF Zone: Zone 3 group was 26.8 (23-30). The BMI (Kg/m²) in the CF Zone: Zone 1 ranged from 23 - 36.62. The BMI (Kg/m²) in the CF Zone: Zone 2 ranged from 18 - 42. The BMI (Kg/m²) in the CF Zone: Zone 3 ranged from 18.6 - 35.04.
There was no significant difference between the groups in terms of BMI (Kg/m²) (χ2 = 2.497, p = 0.287).
Strength of Association (Kendall's Tau) = 0.14 (Small Effect Size)
The Box-and-Whisker plot below depicts the distribution of BMI (Kg/m²) in the 3 groups. The middle horizontal line represents the median BMI (Kg/m²), the upper and lower bounds of the box represent the 75th and the 25th centile of BMI (Kg/m²) respectively, and the upper and lower extent of the whiskers represent the Tukey limits for BMI (Kg/m²) in each of the groups.
Fisher's exact test was used to explore the association between 'CF Zone' and 'BMI' as more than 20% of the total number of cells had an expected count of less than 5.
There was no significant difference between the various groups in terms of distribution of BMI (χ2 = 4.673, p = 0.426).
Strength of association between the two variables (Cramer's V) = 0.28 (Low Association)
Strength of association between the two variables (Bias Corrected Cramer's V) = 0.1 (Little/No Association)
0.0% of the participants in the group [CF Zone: Zone 1] had [BMI: <19.8 Kg/m²]. 14.3% of the participants in the group [CF Zone: Zone 1] had [BMI: 19.8-24.5 Kg/m²]. 85.7% of the participants in the group [CF Zone: Zone 1] had [BMI: 24.5 Kg/m²]. 28.6% of the participants in the group [CF Zone: Zone 2] had [BMI: <19.8 Kg/m²]. 28.6% of the participants in the group [CF Zone: Zone 2] had [BMI: 19.8-24.5 Kg/m²]. 42.9% of the participants in the group [CF Zone: Zone 2] had [BMI: 24.5 Kg/m²]. 6.2% of the participants in the group [CF Zone: Zone 3] had [BMI: <19.8 Kg/m²]. 25.0% of the participants in the group [CF Zone: Zone 3] had [BMI: 19.8-24.5 Kg/m²]. 68.8% of the participants in the group [CF Zone: Zone 3] had [BMI: 24.5 Kg/m²].
Fisher's exact test was used to explore the association between 'CF Zone' and 'Medical Illness' as more than 20% of the total number of cells had an expected count of less than 5.
There was no significant difference between the various groups in terms of distribution of Medical Illness (χ2 = 0.089, p = 1.000).
Strength of association between the two variables (Cramer's V) = 0.05 (Little/No Association)
Strength of association between the two variables (Bias Corrected Cramer's V) = 0 (Little/No Association)
42.9% of the participants in the group [CF Zone: Zone 1] had [Medical Illness: Present]. 57.1% of the participants in the group [CF Zone: Zone 1] had [Medical Illness: Absent]. 42.9% of the participants in the group [CF Zone: Zone 2] had [Medical Illness: Present]. 57.1% of the participants in the group [CF Zone: Zone 2] had [Medical Illness: Absent]. 37.5% of the participants in the group [CF Zone: Zone 3] had [Medical Illness: Present]. 62.5% of the participants in the group [CF Zone: Zone 3] had [Medical Illness: Absent].
Fisher's exact test was used to explore the association between 'CF Zone' and 'Uterine Pathology' as more than 20% of the total number of cells had an expected count of less than 5.
There was a significant difference between the various groups in terms of distribution of Uterine Pathology (χ2 = 6.696, p = 0.028).
Strength of association between the two variables (Cramer's V) = 0.47 (Moderate Association)
Strength of association between the two variables (Bias Corrected Cramer's V) = 0.4 (Moderate Association)
42.9% of the participants in the group [CF Zone: Zone 1] had [Uterine Pathology: Normal]. 57.1% of the participants in the group [CF Zone: Zone 1] had [Uterine Pathology: Present]. 42.9% of the participants in the group [CF Zone: Zone 2] had [Uterine Pathology: Normal]. 57.1% of the participants in the group [CF Zone: Zone 2] had [Uterine Pathology: Present]. 87.5% of the participants in the group [CF Zone: Zone 3] had [Uterine Pathology: Normal]. 12.5% of the participants in the group [CF Zone: Zone 3] had [Uterine Pathology: Present].
Participants in the group CF Zone: Zone 3 had the largest proportion of Uterine Pathology: Normal. Participants in the group CF Zone: Zone 1, Zone 2 had the largest proportion of Uterine Pathology: Present.
The variable ET (mm) was not normally distributed in the 3 subgroups of the variable CF Zone. Thus, non-parametric tests (Kruskal Wallis Test) were used to make group comparisons.
The mean (SD) of ET (mm) in the CF Zone: Zone 1 group was 9.09 (1.15). The mean (SD) of ET (mm) in the CF Zone: Zone 2 group was 8.86 (0.78). The mean (SD) of ET (mm) in the CF Zone: Zone 3 group was 8.93 (1.15). The median (IQR) of ET (mm) in the CF Zone: Zone 1 group was 9 (8.55-9.6). The median (IQR) of ET (mm) in the CF Zone: Zone 2 group was 8.6 (8.3-9.4). The median (IQR) of ET (mm) in the CF Zone: Zone 3 group was 8.85 (8.23-9.7). The ET (mm) in the CF Zone: Zone 1 ranged from 7.3 - 11. The ET (mm) in the CF Zone: Zone 2 ranged from 8 - 10. The ET (mm) in the CF Zone: Zone 3 ranged from 7 - 11.
There was no significant difference between the groups in terms of ET (mm) (χ2 = 0.183, p = 0.912).
Strength of Association (Kendall's Tau) = 0.03 (Little/No Association)
The Box-and-Whisker plot below depicts the distribution of ET (mm) in the 3 groups. The middle horizontal line represents the median ET (mm), the upper and lower bounds of the box represent the 75th and the 25th centile of ET (mm) respectively, and the upper and lower extent of the whiskers represent the Tukey limits for ET (mm) in each of the groups.
The variable βHCG (mIU/mL) was not normally distributed in the 3 subgroups of the variable CF Zone. Thus, non-parametric tests (Kruskal Wallis Test) were used to make group comparisons.
The mean (SD) of βHCG (mIU/mL) in the CF Zone: Zone 1 group was 935.43 (1557.88). The mean (SD) of βHCG (mIU/mL) in the CF Zone: Zone 2 group was 2515.12 (3628.61). The mean (SD) of βHCG (mIU/mL) in the CF Zone: Zone 3 group was 6819.23 (6216.65). The median (IQR) of βHCG (mIU/mL) in the CF Zone: Zone 1 group was 26 (0.81-1139.1). The median (IQR) of βHCG (mIU/mL) in the CF Zone: Zone 2 group was 45 (0.3-4621.5). The median (IQR) of βHCG (mIU/mL) in the CF Zone: Zone 3 group was 4715.5 (2926.5-8691). The βHCG (mIU/mL) in the CF Zone: Zone 1 ranged from 0.2 - 4242. The βHCG (mIU/mL) in the CF Zone: Zone 2 ranged from 0.23 - 8317. The βHCG (mIU/mL) in the CF Zone: Zone 3 ranged from 0.6 - 20275.
There was a significant difference between the 3 groups in terms of βHCG (mIU/mL) (χ2 = 9.012, p = 0.011), with the median βHCG (mIU/mL) being highest in the CF Zone: Zone 3 group.
Strength of Association (Kendall's Tau) = 0.43 (Medium Effect Size)
The Box-and-Whisker plot below depicts the distribution of βHCG (mIU/mL) in the 3 groups. The middle horizontal line represents the median βHCG (mIU/mL), the upper and lower bounds of the box represent the 75th and the 25th centile of βHCG (mIU/mL) respectively, and the upper and lower extent of the whiskers represent the Tukey limits for βHCG (mIU/mL) in each of the groups.
Fisher's exact test was used to explore the association between 'CF Zone' and 'βHCG' as more than 20% of the total number of cells had an expected count of less than 5.
There was a significant difference between the various groups in terms of distribution of βHCG (χ2 = 9.209, p = 0.006).
Strength of association between the two variables (Cramer's V) = 0.55 (High Association)
Strength of association between the two variables (Bias Corrected Cramer's V) = 0.5 (Moderate Association)
57.1% of the participants in the group [CF Zone: Zone 1] had [βHCG: ≤100 mIU/mL]. 42.9% of the participants in the group [CF Zone: Zone 1] had [βHCG: >100 mIU/mL]. 57.1% of the participants in the group [CF Zone: Zone 2] had [βHCG: ≤100 mIU/mL]. 42.9% of the participants in the group [CF Zone: Zone 2] had [βHCG: >100 mIU/mL]. 6.2% of the participants in the group [CF Zone: Zone 3] had [βHCG: ≤100 mIU/mL]. 93.8% of the participants in the group [CF Zone: Zone 3] had [βHCG: >100 mIU/mL].
Participants in the group CF Zone: Zone 1, Zone 2 had the largest proportion of βHCG: ≤100 mIU/mL. Participants in the group CF Zone: Zone 3 had the largest proportion of βHCG: >100 mIU/mL.
Fisher's exact test was used to explore the association between 'CF Zone' and 'Clinical Pregnancy' as more than 20% of the total number of cells had an expected count of less than 5.
There was a significant difference between the various groups in terms of distribution of Clinical Pregnancy (χ2 = 6.696, p = 0.028).
Strength of association between the two variables (Cramer's V) = 0.47 (Moderate Association)
Strength of association between the two variables (Bias Corrected Cramer's V) = 0.4 (Moderate Association)
42.9% of the participants in the group [CF Zone: Zone 1] had [Clinical Pregnancy: Positive]. 57.1% of the participants in the group [CF Zone: Zone 1] had [Clinical Pregnancy: Negative]. 42.9% of the participants in the group [CF Zone: Zone 2] had [Clinical Pregnancy: Positive]. 57.1% of the participants in the group [CF Zone: Zone 2] had [Clinical Pregnancy: Negative]. 87.5% of the participants in the group [CF Zone: Zone 3] had [Clinical Pregnancy: Positive]. 12.5% of the participants in the group [CF Zone: Zone 3] had [Clinical Pregnancy: Negative].
Participants in the group CF Zone: Zone 3 had the largest proportion of Clinical Pregnancy: Positive. Participants in the group CF Zone: Zone 1, Zone 2 had the largest proportion of Clinical Pregnancy: Negative.
Fisher's exact test was used to explore the association between 'CF Zone' and 'Outcome (12 Weeks)' as more than 20% of the total number of cells had an expected count of less than 5.
There was no significant difference between the various groups in terms of distribution of Outcome (12 Weeks) (χ2 = 2.260, p = 0.202).
Strength of association between the two variables (Cramer's V) = 0.34 (Moderate Association)
Strength of association between the two variables (Bias Corrected Cramer's V) = 0.09 (Little/No Association)
66.7% of the participants in the group [CF Zone: Zone 1] had [Outcome (12 Weeks): Viable]. 33.3% of the participants in the group [CF Zone: Zone 1] had [Outcome (12 Weeks): Missed Abortion]. 66.7% of the participants in the group [CF Zone: Zone 2] had [Outcome (12 Weeks): Viable]. 33.3% of the participants in the group [CF Zone: Zone 2] had [Outcome (12 Weeks): Missed Abortion]. 92.9% of the participants in the group [CF Zone: Zone 3] had [Outcome (12 Weeks): Viable]. 7.1% of the participants in the group [CF Zone: Zone 3] had [Outcome (12 Weeks): Missed Abortion].
Discussion
Infertility may be brought on by poor uterine perfusion, which has been linked to unsuccessful use of assisted reproductive technology. By monitoring endometrial thickness and pattern, uterine artery blood flow index, and its embranchment, ultrasound, a non-invasive test frequently employed in clinics, plays a significant role in evaluating endometrial receptivity.(77)
Transvaginal ultrasound is a crucial component of contemporary fertility therapy. According to research employing pulsed and colour Doppler technology, the blood flow to the uterus and ovary undergoes significant variation in relation to cyclic hormonal fluctuations, and this modification can be easily identified using colour Doppler. (69)
Effect On Age and BMI
The mean age of the participants in the present study was found to be 32.83 ± 6.81 years. 36.7 % of the participants were above the age of 35, 56.6% were aged between 26-35 years and the rest 6.7% belonged to the age group of 21-25 years. Each of the three color flow zones had similar mean age and it was not statistically significant.
Although not statistically significant, zone 1 had a higher mean BMI of 30.03 ± 5.00 Kg/m² with the BMI being around 26 for zone 2 and zone 3, suggesting a lower BMI favours higher vascularity of the endometrium. This was concurrent with a study done by Ku et al (78) reported no significant difference in endometrial thickness between women with BMIs below 24 kg/m2 and those with BMIs above 24 kg/m2.
According to Zheng et al, (79) , obesity (BMI more than or equal to 28 kg/m2 appears to have a detrimental effect on endometrial and subendometrial blood flow, but it doesn't appear to have any discernible influence on the results of ICSI in non-PCOS women.
Uterine Pathology
Uterine pathology was found to be statistically significantly associated with the color flow zones with zone 3 showing the maximum (87.5%) normal uterine anatomy and zone 1 and 2 showing 57.5% uterine pathology each in our study.
Endometrial Thickness
In this study, there was no statistically significant relationship between endometrial thickness and the effectiveness of IVF/ICSI cycles in conceiving a baby suggesting that the thickness of the endometrium plays no role in the success of the pregnancy. The highest mean of 9.09 ± 1.15 mm was seen in zone 1. Most of the pregnancies in the current study had the endometrial thickness to be in the range of 8-11mm. Contrasting results were obtained in a study by Kader MA et al (80), wherein it was discovered that the endometrial thickness was substantially connected with the success of IVF/ICSI cycles in conceiving a baby. The endometrial thickness that was most conducive to pregnancy was 8–10 mm (where 50% of women succeeded in conceiving), followed by 10–12 mm (where 25% of women succeeded in conceiving). Only 2.5% of them (those with endometrial thickness greater than 14 mm) were able to become pregnant.
The majority of pregnancies, according to Singh et al. (81), occur between 8 and 10 mm of endometrial thickness. Additionally, he also proposed that there are no documented pregnancies when endometrial thickness is less than 5.8 mm.
According to Okohue et al (82) A higher rate of conception was associated with endometrial thickness of at least 6.5 mm.
Although the effects of endometrial thickness on pregnancy outcomes have been the subject of numerous investigations, the information for measuring endometrial features during each IVF cycle varied amongst these studies.
Clinical Pregnancy Outcome
In the present study it was discovered that there was an improvement in the pregnancy rate with increased endometrial blood flow (subendometrial flow to outer hyperechoic region of endometrium to inner hypoechoic region of endometrium and hyperchogenic cavity). The current study found that 87.5% of the pregnant women had zone III, 42.9% had zone II, and only 42.9% of the pregnant women had zone I. Zone I and II revealed higher rates of negative pregnancy. The association of blood flow zones and clinical pregnancy outcomes was highly significant.
Kader MA et al (80) in his study revealed that 57.5% of pregnant women had zone III blood flow, 37.5% of pregnant women had zone II blood flow and the remaining 5% had zone I blood flow.
There are inconsistent studies on how endometrial vascularity affects IVF pregnancy outcomes. Tekay et al. (86) showed that neither the FET nor the IVF-ET groups' Doppler velocimetry data from conception- and non-conception-cycles differed. It was concluded that poor uterine blood flow hindered implantation and that optimal uterine blood perfusion did not always result in pregnancy.
Our findings concur with those of Applebaum (49).It has been hypothesised that enhanced placental development during pregnancy, which is linked to a decreased risk of miscarriage and a higher likelihood of a live birth after ART, can result from better endometrial and subendometrial vascularity (53).
According to Nagori et al, (87) when endometrial vascularity was observed in zones 3 and 4, compared to zones 1 and 2, the rate of conception was almost twice as high. When the endometrium's vascularity is limited to zones 1 and 2, the abortion rates are similarly very high.
According to Dechaud et al. (88), the endometrial pattern, thickness, and end-diastolic blood flow were the most reliable indicators of uterine receptivity.
In contrast to Aghahoseini et al. (89) suggestion of a negative association, Wang et al. (44) suggested a favourable link between the endometrium and subendometrial blood flows and the success of IVF/ET.
According to Sardana et al. (51), regular clinical practise should include the combination of endometrial thickness and Doppler examination of endometrial blood flow as a quick and efficient way to enhance the success of IVF/ET . This was in support of the findings of the present study.
According to Zaidi et al. (90), failure of implantation was linked to a lack of blood flow in the endometrium and subendometrial zones. Additionally, although there was no statistically significant difference, the pregnancy rates were correlated with the zones of vascular penetration into the subendometrial and endometrial areas (26.7% for zone 1, 36.4% for zone 2, and 37.9% for zone 3).
Similar to this, Chien et al (91) discovered that the rates of pregnancy and implantation rates were 7.5 and 3.5% respectively for patients without detectable endometrial-subendometrial blood flow and 47.8 and 24.2% for those with blood flow in both endometrium as well as the sub-endometrium only while it was 29.7 and 15.8% with blood flow in the sub-endometrium alone. It was concluded that the pattern of endometrial and subendometrial blood flow as measured by transvaginal Color Doppler before endometrial thickness is associated with implantation and pregnancy rates.
Effect on βhcg and Clinical Pregnancy
20 (66.7%) of the participants had βhCG levels above 100 mIU/mL which lead to a positive clinical pregnancy, out of which 17 were viable. The relationship between the color flow zones and βhCG was highly statistically significant with the zone 3 having the highest mean i.e 6819.23 ± 6216.65 mIU/mL.
Poikkeus P et al. discovered identical HCG levels in cycles of fresh and frozen embryo transfer, as well as in the frozen embryo transfer group separated into natural and substituted cycles. (93). On the contrary, lower HCG concentrations were found 16 days after embryo transfer in ICSI compared to IVF in the subgroup of undiagnosed infertility, according to a prior study (94). The reason behind it is unclear. Although ICSI-derived embryos' early embryo cleavage is delayed and their embryonic fragmentation is enhanced, they have equivalent implantation potential to IVF-derived embryos. (95)
There are various restrictions on the study. The sample size was relatively small, and the ability to distinguish between women who conceived and those who did not was insufficient to identify tiny variations. Second, neither the embryo quality nor the index stimulation cycle were examined in this investigation. This was due to the fact that, rather than focusing on the results of the hormone-stimulated FET cycles, the main goal was to evaluate alterations in the endometrial and sub-endometrial blood flow. No attempt was made to test the intra- and interobserver reproducibility of measurements, and continuous data were not always available because not all individuals were assessed at each time point.
The quality of the embryo and the uterine receptivity have major roles in the success of in vitro fertilisation and embryo transfer (IVF-ET) cycles. Evaluation of endometrial receptivity in relation to uterine receptivity remains difficult in assisted reproductive technologies (ART). A standard ultrasonographic examination has been used for because it enables precise and noninvasive endometrial assessment during ART treatment.
Our research revealed that the pregnancy and implantation rates were greater in patients with endometrial blood flow that could be identified. As a result, there was a significant correlation between the endometrium's blood supply and distribution and the likelihood of embryo implantation and development, proving the significance of monitoring for endometrial blood flow when predicting the results of IVF-ET.
Conclusion
There was a statistically significant improvement in the pregnancy rate with increased endometrial blood flow, although there was no statistically significant relationship between endometrial thickness and the effectiveness of IVF/ICSI cycles in conceiving a baby;. It was also noted that beta hCG levels above 100 mIU/mL increase the chances for a positive clinical pregnancy.
With enhanced endometrial blood flow on color doppler in FET cycles, clinical pregnancy rate and implantation rate both considerably rise. Therefore, it is recommended that endometrial thickness and Doppler analysis of endometrial blood flow be combined as a straightforward and efficient method for increasing clinical pregnancy rate in FET cycles. This method should be adopted as standard clinical practise.
References
1. Vander Borght M, Wyns C. Fertility and infertility: Definition and epidemiology. Clin Biochem. 2018;62:2-10.
2. Inhorn MC, Patrizio P, Infertility around the globe: new thinking on gender, reproductive technologies and global movements in the 21st century, Hum. Reprod. Update,2015;21(4):411–426.
3. Hart RJ. Physiological aspects of female fertility: role of the environment, modern lifestyle, and genetics. Physiol Rev,2016;96 (3):873–909.
4. Centre for Medically Assisted Procreation Success rates in IVF between October 1, 1999 and December 31, 2009 http://www.cpma.ch/en/patients/rates-of-success/index/index/ivf.html.
5. Wilcox AJ, Weinberg CR, O’Connor JF, Baird DD, Schlatterer JP, Canfield RE, Armstrong EG, Nisula BC. Incidence of early loss of pregnancy. N Engl J Med,1988; 319: 189–194.
6. Nikas G, Psychoyos A. Uterine pinopodes in peri-implantation human endometrium. Clinical relevance. Ann NY Acad Sci, 1997; 816: 129–142.
7. Abdalla HI, Brooks AA, Johnson MR, Kirkland A, Thomas A and Studd JWW. Endometrial thickness: a predictor of implantation in ovum recipients? Hum Reprod, 1994;9:363-365.
8. Noyes N, Liu H-C, Sultan K, Schattman G and Rosenwaks Z. Endometrial thickness appears to be a significant factor in embryo implantation in in-vitro fertilization. Hum Reprod, 1995;10:919-922.
9. Bakos O, Lundkvist O and Bergh T.Trans vaginal sonographic evaluation of endometrial growth and texture in spontaneous ovulatory cycles - a descriptive study. Hum Reprod,1993;8, 799-806.
10. Dorostghoal M, Ghaffari HOA, Marmazi F, Keikhah N. Overexpression of endometrial estrogen receptor-alpha in the window of implantation in women with unexplained infertility. Int J Fertil Steril 2018;12:37–42.
11. Lessey BA, Young S. Structure, function, and evaluation of the female reproductive tract. In: Strauss JF III, Barbieri RL, editors. Yen & Jaffe’s reproductive endocrinology physiology, pathophysiology, and clinical management. Philadelphia: Elsevier; 2019:206–47.
12. O’Connor KA, Holman DJ, Wood JW: Declining fecundity and ovarian ageing in natural fertility populations. Maturitas. 1998; 30(2): 127–36.
13. Achache H, Revel A: Endometrial receptivity markers, the journey to successful embryo implantation. Hum Reprod Update. 2006; 12(6): 731–46.
14. Bergh PA, Navot D: The impact of embryonic development and endometrial maturity on the timing of implantation. Fertil Steril. 1992; 58(3): 537–42.
15. Gurgan T, Demirol A. Why and how should multiple pregnancies be prevented in assisted reproduction treatment programmes? Reprod Biomed Online. 2004;9:237–44.
16. Shapiro BS, Daneshmand ST, Garner FC, Aguirre M, Hudson C, Thomas S. Evidence of impaired endometrial receptivity after ovarian stimulation for in vitro fertilization: a prospective randomized trial comparing fresh and frozen–thawed embryo transfer in normal responders. Fertil Steril. 96(2):344–8.
17. Behr B. and Shu Y. Cryopreservation of Pronuclear Stage Human Embryos. In: Chian, R. and Quinn, P., Eds., Fertility Cryopreservation, Cambridge University Press, Cambridge, 2010, 76-88.
18. van Eekelen R, van Geloven N, van Wely M, Bhattacharya S, van der Veen F, Eijkemans MJ, McLernon DJ. IVF for unexplained subfertility; whom should we treat? Hum Reprod. 2019 Jul 8;34(7):1249-1259.
19. Noyes RW, Hertig AT, Rock J: Dating the endometrial biopsy. Am J Obstet Gynecol 1975, 122:262-263.
20. Schild RL, Knobloch C, Dorn C, Fimmers R, van der Ven H, Hansmann M: Endometrial receptivity in-vitro fertilization program assessed by spiral artery blood flow, endometrial thickness, endometrial volume and uterine artery blood flow. Fertil Steril 2001, 7:361-366.
21. Issacs JD, Wells CS, William DB, Odem RR, Gast MJ, Strickler RC: Endometrial thickness is a valid monitoring parameter in cycles of ovulation induction with menotropins alone. Fertil Steril 1996, 65:262-266.
22. Ng EH, Chan CC, Tang OS, Yeung WS, Ho PC: The role of endometrial and subendometrial blood flows measured by three-dimensional power Doppler ultrasound in the prediction of pregnancy during IVF treatment. Human Reprod 2006, 21:164-170.
23. Casper RF: It’s time to pay attention to the endometrium. Fertil Steril 2011, 96:519–521.
24. Rossman I, Bartelmez GW. The injection of the blood vascular system of the uterus. Anat Rec 1957;128: 223–31.
25. Catt JW, Henman M. Toxic effects of oxygen on human embryo development. Hum Reprod 2000; 15(Suppl 2):199–206.
26. Yang HW, Hwang KJ, Kwon HC, Kim HS, Choi KW, Oh KS. Detection of reactive oxygen species (ROS) and apoptosis in human fragmented embryos. Hum Reprod 1998;13:998–1002.
27. Weissman A, Gotlieb L, Casper RF: The detrimental effect of increased endometrial thickness on implantation and pregnancy rates and outcome in an in vitro fertilization program. Fertil Steril 1999, 71:147–149.
28. Rashidi BH, Sadeghi M, Jafarabadi M, Tehrani Nejad ES: Relationships between pregnancy rates following in vitro fertilization or intracytoplasmic sperm injection and endometrial thickness and pattern. Eur J Obstet Gynecol Reprod Biol 2005, 120:179–184.
29. Richter KS, Bugge KR, Bromer JG, Levy MJ: Relationship between endometrial thickness and embryo implantation, based on 1,294 cycles of in vitro fertilization with transfer of two blastocyst-stage embryos. Fertil Steril 2007, 87:53–59.
30. Ai-Ghamdi A, Coskun S, AL-Rejjal R, Awartani K: The correlation between endometrial thickness and outcome of in vitro fertilization and embryo transfer (IVF-ET) outcome. Reprod Biol Endocrinol 2008, 6:37.
31. Dietterich C, Check JH, Choe JK, Nazari A, Lurie D: Increased endometrial thickness on the day of human chorionic gonadotropin injection does not adversely affect pregnancy or implantation rates following in vitro fertilization-embryo transfer. Fertil Steril. 2002, 77: 781-786.
32. Wang L, Qiao J, Li R, Zhen X, Liu Z. Role of endometrial blood flow assessment with color Doppler energy in predicting pregnancy outcome of IVF-ET cycles. Reprod Biol Endocrinol. 2010; 18;8:122.
33. Lesny P, Killick SR, Tetlow RL, Manton DJ, Robinson J, Maguiness SD: Ultrasound evaluation of the uterine zonal anatomy during in-vitro fertilization and embryo transfer. Hum Reprod 1999, 14:1593-1598.
34. Zhao J, Zhang Q, Li Y. The effect of endometrial thickness and pattern measured by ultrasonography on pregnancy outcomes during IVF-ET cycles. Reprod Biol Endocrinol. 2012;10(1):100.
35. Sher G, Herbert C, Maassarani, G, Jacobs MH. Assessment of the late proliferative phase endometrium by ultrasonography in patients undergoing in-vitro fertilization and embryo transfer (IVF/ET). Hum Reprod 1991;6:232-37.
36. Applebaum M. The uterine biophysical profile. Ultrasound Obstet Gynecol 1995;5(1):67-68.
37. Murphy KJ and Rubin JM. Power Doppler: it’s a good thing. Semin. Ultrasound, CT, and MRI. 1997;18:13–21.
38. Ng EHY, Chan CCW, Tang OS, WSB Yeung, Ho PC. Changes in endometrial and subendometrial blood flows in IVF. Reproductive BioMedicine Online 2009;18:269-75.
39. CDC. American Society for Reproductive Medicine; Society for Assisted Reproductive Technology. 2016 assisted reproductive technology national summary report. Atlanta, GA: US Department of Health and Human Services, CDC. (2018).
40. Casper RF, Yanushpolsky EH. Optimal endometrial preparation for frozen embryo transfer cycles: window of implantation and progesterone support. Fertil Steril. 2016;105(4):867–72.
41. El-Toukhy T, Coomarasamy A, Khairy M, Sunkara K, Seed P, Khalaf Y, et al. The relationship between endometrial thickness and outcome of medicated frozen embryo replacement cycles. Fertil Steril. 2008;89:832–9.
42. Weissman A, Leong M, Sauer MV & Shoham Z. Characterizing the practice of oocyte donation: a web-based international survey. Reprod Biomed Online,2014;28:443–450.
43. Dal Prato L, Borini A, Cattoli M, Bonu MA, Sciajno R, Flamigni C. Endometrial preparation for frozen-thawed embryo transfer with or without pretreatment with gonadotropin-releasing hormone agonist. Fertil Steril. 2002;77:956–60.
44. Mackens S. et al. Frozen embryo transfer: a review on the optimal endometrial preparation and timing. Hum Reprod,2017; 32: 2234–2242.
45. Devroey P, Polyzos NP, Blockeel C. An OHSS-Free clinic by segmentation of IVF treatment. Hum Reprod. 2011;26(10):2593–2597.
46. Sardana D, Upadhyay AJ, Deepika K, Pranesh GT, & Rao KA. Correlation of subendometrial-endometrial blood flow assessment by two-dimensional power Doppler with pregnancy outcome in frozen-thawed embryo transfer cycles. Journal of human reproductive sciences,2014;7(2):130–135).
47. Bardos J, Rodriguez-Purata J, Whitehouse MC, Lee JA, Sandler AB, Stein DE, Copperman AB. Optimal endometrial preparation for frozen embryo transfer (FET) of screened embryos is independent of follicular phase length. Fertility and Sterility, 2015;104(3):Suppl E47-E4.
48. Khan MS, Shaikh A, Ratnani R. Ultrasonography and Doppler Study to Predict Uterine Receptivity in Infertile Patients Undergoing Embryo Transfer The Journal of Obstetrics and Gynecology of India (September–October 2016); 66(S1):S377–S382.
49. Elsharkawy S , Mahmoud T, Elsedeek M, and Amer E. Endometrial Preparation for Frozen Embryo Transfer by Supplemented Natural Cycle versus Hormone Replacement Cycle in Regularly Cycling Women. Open Journal of Obstetrics and Gynecology, 2019;9:827-837.
50. Shaodi Z, Qiuyuan L, Yisha Y, Cuilian Z. The effect of endometrial thickness on pregnancy outcomes of frozen-thawed embryo transfer cycles which underwent hormone replacement therapy. PLOS ONE. 2020 Sep 24;15(9):e0239120.
51. Pandurangi M, Reddy NS, Rani GU, Kirubamani H, Radha V, Siddhartha N. Does the Pattern of Endometrium Influence the Frozen Embryo Transfer Cycle Outcome? Journal of Clinical and Diagnostic Research. 2021;15(11): QC12-QC15.
52. Li L, Dan-Dan G, Yi Z, Jing-Yan S & Zhen-Gao S. Comparison of Stimulated Cycles with Low Dose r-FSH versus Hormone Replacement Cycles for Endometrial Preparation Prior to Frozen-Thawed Embryo Transfer in Young Women with Polycystic Ovarian Syndrome: A Single-Center Retrospective Cohort Study from China, Drug Design, Development and Therapy, 2021: 2805-2813.
53. Eleftheriadou A, Francis A,Wilcox M, Jayaprakasan K. Frozen Blastocyst Embryo Transfer: Comparison of Protocols and Factors Influencing Outcome. J. Clin. Med, 2022;11(3): 737.