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 >= 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 (>= 37 weeks) and nonlow birthweight (>= 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. (Fertil Steril (R) 2009;91:2586-92. (c) 2009 by American Society for Reproductive Medicine.)