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.