Impact of a Previous CS on the Ongoing Pregnancy Rate in Single Euploid Frozen Embryo Transfer (ET)

Study Overview
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Brief Summary
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As embryo ploidy is a crucial factor not only for implantation but also for maintenance of a pregnancy, the aim of this study is to evaluate the impact of the CS / isthmocele on the ongoing pregnancy rates and the implantation site in single euploid frozen embryo transfer, independent of the endometrial preparation approach.

Detailed Description
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The impact of a previous CS on the future fertility in the general population is discussed controversially, but it seems that the clinical and social circumstances leading to the CS have a greater effect on future fertility than the surgical procedure itself (Gurol-Urganci et al., 2013, 2014; Evers et al., 2014). However, this might be different in women who do not conceive spontaneously after a previous CS and need to undergo ART due to secondary infertility. Whereas some studies describe a reduction of implantation, ongoing pregnancy, and live birth (LB) rates (Vissers et al., 2020; Wang et al., 2020; Diao et al., 2021; Friedenthal et al., 2021; van den Tweel et al., 2022), others describe a negative impact of a previous CS only in the presence of an isthmocele (Diao et al., 2021) or no impact (Patounakis et al., 2016). A case control study evaluated whether there are any differences in the location and distance to the internal cervical ostium of the implantation site of the intrauterine gestation sacs, early pregnancy symptoms and pregnancy outcome at 12 weeks gestation between women with and without a previous Caesarean section (CS) in patients who conceived naturally (Naji et al., 2013). Investigators concluded that the presence of a CS scar affects the site of implantation, and also that the distance between implantation site and the scar is related to the risk of spontaneous abortion. This is a purely observational study without any intervention. Participants will be stratified into different groups according to their previous obstetrical history. Total sample size will include 1050 participants undergoing a frozen embryo transfer (FET) cycle. Isthmocele will be defined according to de Vaate et al (Bij de Vaate et al., 2011) as: visible anechogenic area of at least 1 mm depth at the site of the Cesarean scar.

Official Title
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To Study the Impact of a Previous Cesarean Section (CS) With / Without an Isthmocele on the Ongoing Pregnancy Rate in Single Euploid Frozen Embryo Transfer

Conditions
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Infertility, Implantation

Intervention / Treatment
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* Diagnostic Test: Ultrasound between 6+0 and 6+7 weeks of pregnancy - With Isthmocele
* Diagnostic Test: Ultrasound between 6+0 and 6+7 weeks of pregnancy - Without Isthmocele
* Diagnostic Test: Ultrasound between 6+0 and 6+7 weeks of pregnancy


Participation Criteria
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Eligibility Criteria
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Inclusion Criteria: - All participants undergoing a single euploid FET, independent of the endometrial preparation approach Exclusion Criteria: Intracavitary fluid during preparation for FET Known anomaly of the uterus or the adnexae (e.g.: fibroids, polyps, hydrosalpinx, endometriosis, adenomyosis) Embryo which was biopsied on day 7 Poor quality embryo which was transferred (Gardner criteria: AC / BC / CB, biopsied on day 6 and CC embryos from both, day 5 and day 6 biopsies, classified as poor quality embryos) History of recurrent abortion Antiphospholipid syndrome / autoimmune diseases

Ages Eligible for Study
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Minimum Age: 18 Years
Maximum Age: 42 Years

Sexes Eligible for Study
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Female

Study Plan
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How is the study designed?
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Arms and Interventions

| Participant Group/Arm | Intervention/Treatment |
| --- | --- |
| One CS with isthmocele<br> | Diagnostic Test: Ultrasound between 6+0 and 6+7 weeks of pregnancy - With Isthmocele<br>* Location of implantation of the GS (gestational sac) amended to Naji et al, defined as 3 possible implantation sites: (A: fundal, B: anterior, C: posterior) Size of isthmocele: Depth of isthmocele Width of isthmocele Circumference of isthmocele Distance between isthmocele and outer cervical os (measured with the trace line) Distance between CS scar and outer cervical os (measured with the trace line) Size of gestational sac Measurements of the isthmocele size / circumference / distance between isthmocele / CS and outer cervical os<br>|
| More than one CS with Isthmocele<br> | Diagnostic Test: Ultrasound between 6+0 and 6+7 weeks of pregnancy - With Isthmocele<br>* Location of implantation of the GS (gestational sac) amended to Naji et al, defined as 3 possible implantation sites: (A: fundal, B: anterior, C: posterior) Size of isthmocele: Depth of isthmocele Width of isthmocele Circumference of isthmocele Distance between isthmocele and outer cervical os (measured with the trace line) Distance between CS scar and outer cervical os (measured with the trace line) Size of gestational sac Measurements of the isthmocele size / circumference / distance between isthmocele / CS and outer cervical os<br>|
| One or more CS without isthmocele<br> | Diagnostic Test: Ultrasound between 6+0 and 6+7 weeks of pregnancy - Without Isthmocele<br>* Location of implantation of the GS amended to Naji et al, defined as 3 possible implantation sites: (A: fundal, B: anterior, C: posterior) Distance between CS scar and outer cervical os (measured with the trace line) Size of gestational sac<br>|
| With previous vaginal delivery<br> | Diagnostic Test: Ultrasound between 6+0 and 6+7 weeks of pregnancy<br>* Location of implantation of the GS (gestational sac) amended to Naji et al, defined as 3 possible implantation sites (A: fundal, B: anterior, C: posterior) Size of gestational sac<br>|
| With first ongoing pregnancy<br> | Diagnostic Test: Ultrasound between 6+0 and 6+7 weeks of pregnancy<br>* Location of implantation of the GS (gestational sac) amended to Naji et al, defined as 3 possible implantation sites (A: fundal, B: anterior, C: posterior) Size of gestational sac<br>|

What is the study measuring?
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Primary Outcome Measures

| Outcome Measure | Measure Description | Time Frame |
| --- | --- | --- |
| Ongoing pregnancy rate |  | 5 weeks | 
| Implantation rate | Number of gestational sacs observed by ultrasound at 6 weeks of gestation divided by the number of embryos transferred | 6 weeks | 
| Implantation site |  | 6 weeks | 
| Rate of vaginal bleeding in early pregnancy (until 12 weeks of gestation) |  | 12 weeks | 

 Terms related to the study
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Keywords Provided by Centre Hospitalier Valida
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Implantation, Infertility, Isthmocele, Cesarean section