Effect of body weight on early hormone levels in singleton pregnancies resulting in delivery after in vitro fertilization.

OBJECTIVE: To evaluate which clinical characteristics influence early maternal β-human chorionic gonadotropin (hCG) and progesterone levels in in vitro fertilization (IVF) pregnancies.

DESIGN: Retrospective cohort analysis.

SETTING: Academic medical center.

PATIENT(S): Women with a live birth after single-blastocyst embryo transfer in either a fresh or frozen cycle between 2004 and 2017, comprising 1,282 pregnancies in 1,057 patients.

INTERVENTION(S): None.

MAIN OUTCOME MEASURE(S): The initial human chorionic gonadotropin concentration (β-hCG1) measured a mean of 10 days (range: 9-12 days) after embryo transfer, the rate of increase in β-hCG concentrations, and progesterone concentration, with all analyses controlled for number of days between the embryo transfer and the β-hCG1 measurement.

RESULT(S): The clinical factor that positively influenced the β-hCG1 level in the fresh cycle was the stimulation type (antagonist cycle higher than long agonist cycle). The clinical factors that negatively influenced both fresh and frozen cycle β-hCG1 were lower embryo quality and increasing body weight. Increasing weight negatively impacted progesterone levels in both fresh and frozen cycles. A 100 lb (45.4 kg) difference in weight was associated with a 34.8% reduction in β-hCG1 for both fresh and frozen cycle pregnancies. The rate of increase in β-hCG was unaffected by body weight. A 100 lb (45.4 kg) difference in weight was associated with a 53.3% and a 32.8% reduction in progesterone in fresh and frozen cycles, respectively.

CONCLUSION(S): Increasing body weight is associated with significantly lower β-hCG and progesterone concentrations in early pregnancy after blastocyst single-embryo transfer in both fresh and frozen cycles. Clinicians should consider this when evaluating these hormone levels for prognostic and diagnostic purposes.