P–357 The risk factors for early pregnancy loss based on a logistic model following 13,977 infertile patients after in vitro fertilization
Authors: Ouyang Y , Li X , Cai P 
Published: August 2021

Abstract

Study question
What are the risk factors for early pregnancy loss (EPL) after in vitro fertilization-embryo transfer (IVF-ET)?

Summary answer
The maternal age, gestational sac diameter, embryonic length, yolk sac diameter, heart rate of day 27–29 and endometrium thickness on transfer day were risk factors. What is known already: The first routine ultrasound scan is commonly arranged on day 27–29 after IVF-ET in most reproductive centers in China to determine the location and viability of the embryo. Individual maternal factors, such as a high maternal age (MA) and abnormal ultrasound parameters such as embryonic bradycardia and excessively large or small yolk sac diameter (YSD) have been shown to be associated with pregnancy failures. However, few studies focused on the risk factors of the IVF population, and little is known about the clinical meaning of ultrasound indicators of 27–29 days after transplantation.

Study design, size, duration
This was a retrospective study in a single reproductive centre. The infertile patients included in this study underwent IVF treatment between June 2016 to December 2017. Participants/materials, setting, methods: During this period, 13,977 women were identified with a singleton pregnancy by TVS at day 27–29 after IVF-ET. The gestational sac diameter (GSD), embryonic length (EL), embryonic heart rate (EHR) and YSD and the presence of intrauterine hematoma (IUH) were measured. The clinical characteristics were also collected. The first trimester pregnancy outcome of these women was noted at 12 weeks of gestation. A backward Wald logistic regression model was established to screen the risk factors.

Main results and the role of chance
1,926 cases of spontaneous miscarriage ≤12 weeks of gestation, which were assigned as EPL and 12,051 women with an ongoing pregnancy for &gt;12 weeks of gestation.
When compared with the ongoing pregnancy group, the MA, infertility duration and transfer cycle were significantly higher, and the day–14 human chorionic gonadotrophin and the endometrium (EM) thickness on transfer day were significantly lower in the EPL group (p &lt; 0.001). Based on the TVS measurements, the GSD (18.5±3.6 vs. 13.2±4.8 mm), EL (3.5±0.9 vs. 1.2±1.6 mm), YSD (3.6±0.4 vs. 2.6±1.5 mm) and EHR (114.5±12.2 vs. 42.4±53.5 bpm) were significantly greater in the ongoing pregnancy group than those in the EPL group (p &lt; 0.001). The incidence of IUH (16.0% vs. 18.8%, P = 0.002) was also markedly higher in the EPL group
MA, GSD, EL, YSD, EHR and EM on transfer day finally entered the logistic model after stepwise screening. The probability of EPL was: exp(z)/(1 + exp(z)), where z = 2.432 + (0.092 × MA) - (0.074 × EM) - (0.114 ×GSD) - (0.245 × EL) - (0.034 × HR) - (0.159 × YSD).

Limitations, reasons for caution
Data on smoking and clinical symptoms such as vaginal bleeding or abdominal pain were not included in the final analysis which might be possible risk factors. These predictors were derived from an IVF population, the situation may not be the same in the general population.
Wider implications of the findings: The risk factors for EPL after IVF-ET are clearly identified in this study. The logistic model which incorporates readily available data that are routinely collected in clinical practice could be used for calculating the risk of EPL and effectively guide subsequent medical plans.

Trial registration number
None