Fertil Steril. 2025 Aug 25:S0015-0282(25)01844-8. doi: 10.1016/j.fertnstert.2025.08.020. Online ahead of print.
ABSTRACT
OBJECTIVE: To compare the perinatal outcomes between fresh and frozen embryo transfer strategies among ongoing pregnancies conceived by IVF/ICSI.
DESIGN: A prospective cohort study. The study was conducted within the framework of a hypothetical randomized controlled trial, so as to enhance the validity of the evidence obtained from observational data.
SETTING: 50 study sites in 17 provinces of China.
SUBJECTS: From November 2017 to August 2021, 5118 pregnant women who conceived by IVF/ICSI were recruited in their first trimester.
EXPOSURE: Frozen versus fresh embryo transfer.
MAIN OUTCOME MEASURES: The primary outcome was perinatal complications, defined as any occurrence of perinatal death or birth defects. The secondary outcomes included preterm birth, small for gestational age, large for gestational age, low birth weight, and macrosomia. The safety outcomes were abortion, pregnancy-induced hypertension, gestational diabetes mellitus, and gestational thyroid dysfunction.
RESULTS: A total of 2856 pregnant women were included in the analysis, with the allocation ratio of 1:1. The perinatal complication rate of the frozen embryo transfer group (5.0%, 72/1428) was similar to that of the fresh embryo transfer group (4.6%, 66/1428), with the RR of 1.09 (95% CI, 0.79 to 1.51). Moreover, there was no significant difference in the risks of preterm birth, small for gestational age, large for gestational age, low birth weight, and macrosomia between the two groups. However, compared to fresh embryo transfer, frozen embryo transfer was associated with an increased risk of pregnancy-induced hypertension (RR, 2.18; 95% CI, 1.10 to 4.62).
CONCLUSION: The risk of perinatal complications was similar between fresh and frozen embryo transfer strategies, while the risk of pregnancy-induced hypertension seemed to be higher for frozen embryo transfer strategy among ongoing pregnancies. Therefore, the decision on fresh or frozen embryo transfer should be more cautious, with careful consideration of the benefits and potential risks.
PMID:40865754 | DOI:10.1016/j.fertnstert.2025.08.020