AUTHOR=Yang Ai-Min , Xu Xiuhua , Han Yan , Wei Jian-Jun , Hao Gui-Min , Cui Na , Zhao Zhi-Ming , Wang Wei , Huang Xianghua 

TITLE=Risk Factors for Different Types of Pregnancy Losses: Analysis of 15,210 Pregnancies After Embryo Transfer

JOURNAL=Frontiers in Endocrinology

VOLUME=Volume 12 - 2021

YEAR=2021

URL=https://www.frontiersin.org/journals/endocrinology/articles/10.3389/fendo.2021.683236

DOI=10.3389/fendo.2021.683236

ISSN=1664-2392

ABSTRACT=Objective: To evaluate the risk factors for different types of pregnancy losses after embryo transfer (ET). 
Design: Retrospective cohort study
Setting: Reproductive medicine center
Participants: 15210 pregnancies after fresh and frozen-thawed embryo transfer between January 2014 and June 2019. 
Main outcome measures: The primary outcome was pregnancy loss (PL) throughout the entire pregnancy. Secondary outcomes were non-visualized PL, early miscarriage, late miscarriage, stillbirth.
Methods: The effect of patients’ baseline characteristics and IVF/ICSI cycle-specific factors on the risk of PL after fresh and frozen-thawed ET was determined by multivariate logistic regression analysis. 
Results: Compared to women under 35 years old, those between 35 and 40 had an increased risk of early miscarriage (odds ratio [OR] 1.49, 95% confidence interval [CI] 1.22-1.83), while those after 40 appeared to have an increased risk of both early miscarriage (OR 3.82, 95% CI 2.65-5.51) and late miscarriage (OR 2.79, 95% CI 1.64-4.77). Overweight patients were observed to have a higher risk of late miscarriage (OR 1.38, 95% CI 1.16-1.65), while obese patients showed a higher risk of both early miscarriage (OR1.47, 95% CI 1.14-1.91) and late miscarriage (OR1.80, 95% CI 1.33-2.44). Polycystic ovary syndrome (PCOS) was an independent risk factor for late miscarriage (OR1.58, 95% CI 1.28-1.96), and the detrimental effect of PCOS was independent of obesity status. Women with uterine factors had a higher risk of early miscarriage (OR 1.77 (95% CI 1.32-2.38) than women without uterine factors. A negative correlation was observed between the thickness of endometrium and PL (OR 0.95 95% CI 0.92-0.97). There was an increased risk of PL after frozen-thawed ET versus fresh ET (OR1.12, 95% CI 1.01-1.24). Women who transferred ≥2 embryos showed lower risk of overall PL than women transferred single embryo, with adjusted ORs ranged from 0.57~0.94. However, women who transferred 3 embryos demonstrated a higher risk of late miscarriage than women transferred single embryo (OR 2.23, 95% CI 1.36-3.66).
Conclusions: Patients with uterine factors demonstrated higher risk of early miscarriage and stillbirth. Overweight, PCOS and transferred 3 embryos associated with late miscarriage. Aged 40 and over, obesity, frozen embryo transfer associated with early and late miscarriage.