Pregnancy outcome after fetal reduction in women with a dichorionic twin pregnancy

Study question: What are the pregnancy outcomes for women with a twin pregnancy that is reduced to a singleton pregnancy?

Summary answer: Fetal reduction of a twin pregnancy significantly improves gestational age at birth and neonatal birthweight, however at an increased risk of pregnancy loss and preterm delivery.

What is known already: Women with a multiple pregnancy are at increased risk for preterm delivery. Fetal reduction can be considered in these women.

Study design, size, and duration: Retrospective cohort study of 118 women with a twin pregnancy reduced to a singleton pregnancy between 2000 and 2010.

Participants/materials, setting, and methods: We compared the outcome of pregnancy in consecutive women with a dichorionic twin pregnancy that was reduced to a singleton pregnancy to that of women with a dichorionic twin pregnancy that was managed expectantly and women with a primary singleton pregnancy. Reductions were performed between 10-23(6/7) weeks' gestation by intracardiac or intrathoracic injection of potassium chloride, mostly for congenital anomalies. We compared median gestational age, pregnancy loss <24 weeks, preterm delivery <32 weeks, neonatal birthweight and perinatal deaths.

Main results and the role of chance: We studied 118 women with a twin pregnancy that was reduced to a singleton, 818 women with an ongoing dichorionic twin pregnancy and 611 women with a primary singleton pregnancy. Loss of the entire pregnancy <24 weeks and preterm delivery occurred significantly more in the reduction group compared with the ongoing twin group (11.9 versus 3.1% <24 weeks, P< 0.001 and 18.6 versus 11.5% <32 weeks, respectively, P < 0.001). In the reduction group, the percentage of women without any surviving child was significantly higher compared with the ongoing twin and primary singleton group (14.4, 3.4 and 0.7%, respectively, P < 0.001). Median gestational age was 38.9 weeks (interquartile range (IQR) 34.7-40.3) for reduced pregnancies, 37.1 weeks (IQR 35.3-38.1) for ongoing twin pregnancies and 40.1 (IQR 39.1-40.9) for primary singletons (P < 0.001 for all comparisons).

Limitations, reasons for caution: The main limitations of the study were its retrospective character, and the fact that indications for reduction were heterogeneous.

Wider implications of the findings: In women with a dichorionic twin pregnancy fetal reduction increases median gestational age only at considerable risk of complete early pregnancy loss.

Study funding/competing interests: The study was not funded. None of the authors has conflicts of interest.