Corpus luteum formation in frozen embryo transfer and offspring growth trajectories: a prospective cohort study

What are the effects of different endometrial preparation protocols in frozen embryo transfer (FET) cycles on offspring growth, and does the presence or absence of corpus luteum formation influence growth trajectories of children from birth to 3 years?

Prospective cohort study based on the Jiangsu Birth Cohort (n = 1956 singleton live births after FET between November 2017 and October 2022). Participants were categorized into the 'corpus luteum forming' (CLF), including true natural, modified natural and ovulation induction cycles, and 'non-corpus luteum forming' (NCLF), including artificial and GnRHa downregulated artificial cycles groups. Offspring anthropometric measures were collected at nine time points to 3 years. Z-scores were calculated using WHO 2006 standards. Linear mixed models (LMM) and group-based trajectory modelling (GBTM) assessed group differences in growth, adjusting for socioeconomic, maternal and child factors.

Among 1956 families (NCLF: n = 1408; CLF: n = 548), birth measures were comparable. The NCLF group showed lower weight, BMI and related z-scores at 18 months, and lower head circumference z-scores at 24 months, with these differences resolving by 3 years; LMM revealed significantly lower weight-for-age z-scores between 8 and 30 months and lower length-for-age z-scores at 30 months in the NCLF group; and GBTM identified three distinct patterns for both indicators, with no significant differences in trajectory group distribution between groups.

Corpus luteum formation affects early weight and length growth trajectories but has no lasting effect by age 3 years. The developmental safety of different endometrial preparation protocols in children conceived through assisted reproduction is supported.