The Effect of Early Fetal Losses on Singleton Assisted-conception Pregnancy Outcomes

Objective: To evaluate the effect of first trimester fetal losses in singleton births from assisted reproductive technology using data from the Society for Assisted Reproductive Technology national database for 2005.

Design: Historic cohort study.

Setting: Clinic-based data.

Patient(s): The study population included 21,535 singleton deliveries of >or=22 weeks gestation categorized by the number of fetal heartbeats identified on early ultrasound as one, two, three, or more.

Intervention(s): None.

Main Outcome Measure(s): Length of gestation, birthweight, and birthweight for gestation. Odds ratios (ORs) were calculated, with the group with one fetal heartbeat on early ultrasound as the reference.

Result(s): Preterm birth (<37 weeks, OR 1.73; 32-36 weeks, OR 1.59; <32 weeks OR 2.56) and low birthweight (<2,500 g, OR 2.09; 1,500-2,499 g, OR 1.94) increased and term birth and nonlow birthweight decreased (OR 0.52 and 0.48) with more than one fetal heartbeat.

Conclusion(s): Early fetal loss in pregnancies that result in a singleton live birth is associated with significantly increased odds for lowered birthweight, shortened gestation, and reduced birthweight for age. Because first trimester multiple fetal heartbeats are more common in assisted-conception pregnancies than in unassisted pregnancies, this factor may help explain the greater risk for reduced birthweight and shorter gestations observed in this population.