The effect of early fetal losses on singleton assisted-conception pregnancy outcomes

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.

Historic cohort study.

Clinic-based data.

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.

None.

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.

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.

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.