Are in vitro fertilization pregnancies with early spontaneous reduction high risk?

Objective

The objective of the study was to determine whether spontaneous reduction in in vitro fertilization pregnancies results in outcomes comparable with in vitro fertilization singleton pregnancies or ongoing twin pregnancies.

Study design

Women with in vitro fertilization pregnancies from 2003 to 2005 who had first-trimester ultrasound and delivered in our hospital were identified. Those with documented reduction from dichorionic twins to a single viable fetus at 14 weeks or less were categorized as spontaneous reduction pregnancies and were compared with dichorionic twin and singleton pregnancies without reduction.

Results

One hundred sixty-eight singleton, 55 spontaneous reduction, and 86 twin pregnancies were included. Gestational age at delivery was similar in the singleton and spontaneous reduction groups; twins delivered significantly earlier. Spontaneous reduction was associated with lower birth weight than other singleton pregnancies (median 3062 g versus 3425 g; P = .005). The rate of pre-eclampsia was higher in pregnancies with spontaneous reduction, compared with other singleton pregnancies 9.3% versus 2.4%; P = .04).

Conclusion

Spontaneous reduction of a twin to a singleton pregnancy is associated with prolonged gestation and higher birth weight for the remaining fetus.

Key words: In vitro fertilization, Spontaneous reduction, Multifetal pregnancy, Vanishing twin