The contribution of twins conceived by in vitro fertilization to preterm birth rate: observations from a quarter of century

Abstract

AbstractObjectiveLittle information exists related to the contribution of assisted reproductive technology (ART) twins to the preterm and very preterm birth rate. We sought to examine this contribution over a period of more than two decades in a tertiary perinatal center.MethodsWe identified all preterm births from 1993 to 2017, born at <37 or <32 weeks’ gestation, by mode of conception [in vitro fertilization (IVF) vs. non-IVF pregnancies]. We generated trend lines of the annual change of the dependent variable (% preterm birth).ResultsWe evaluated 74,299 births, including 3934 (5.3%) preterm births at <37 and 826 (1.1%) at <32 weeks’ gestation. In this period, 1019 (1.4%) twin pairs were born including 475 (46.6%) and 80 (7.8%) at <37 and <32 weeks, respectively. There were 213 (5.4%) IVF pregnancies among the preterm births at <37 weeks, including 88 (41.3%) twins. Fifteen (1.8%) births of all IVF gestations were at <32 weeks, and all were twins. Whereas the annual rate of spontaneous twins did not change, a significant increase over time exists for IVF twins (P < 0.05, R2 = 0.6). We demonstrated an increase in IVF twin births at <37 weeks but not for spontaneously conceived twins. Whereas the twin birth rate at <32 weeks did not change over time, all preterm births at <32 weeks following IVF were twins.ConclusionThe risk of twins after ART increasingly contributes to preterm births at <37 weeks and ART twins are at significant risk for preterm births at <32 weeks.