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

OBJECTIVE

To evaluate the effect of first trimester fetal losses on twin births from assisted reproductive technology (ART).

DESIGN

Historical cohort study.

SETTING

Clinic-based data.

PATIENT(S): The study population included 9,036 twin pregnancies of >or=22 weeks' gestation in the 2005 Society for Assisted Reproductive Technology Clinic Outcomes Reporting System database, categorized by the presence of three versus two fetal heartbeats on early ultrasound.

INTERVENTION(S): None.

MAIN OUTCOME MEASURE(S): Length of gestation and birthweight. Adjusted odds ratios (AORs) were calculated with the group with two fetal heartbeats on early ultrasound as the reference.

RESULT(S): Increased odds with three fetal heartbeats included <32 weeks, 32-36 weeks, and <37 weeks (AORs 1.47, 1.28, and 1.35, respectively) and very low birthweight (<1,500 g), moderately low birthweight (1,500-2,499 g), and low birthweight (<2,500 g) (AORs 1.69, 1.38, and 1.47, respectively). Significantly decreased odds included term birth (>or=37 weeks) and nonlow birthweight (>or=2,500 g) (AORs 0.74 and 0.68).

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