Preterm Birth or Small for Gestational Age in a Singleton Pregnancy and Risk of Recurrence in a Subsequent Twin Pregnancy

OBJECTIVE: To evaluate whether a history of preterm birth or small for gestational age (SGA) in a singleton pregnancy is associated with an increased risk of recurrence of the same condition in a subsequent twin pregnancy. METHODS: Retrospective cohort study of twin pregnancies delivered in one maternal–fetal medicine practice from 2005 to 2014. Patients with a history of singleton preterm birth at less than 37 weeks of gestation were compared with patients with a history of singleton term birth and nulliparous patients. A similar analysis was performed for a history of SGA (birth weight less than 10%). RESULTS: Six hundred forty-seven twin pregnancies were included. The prior singleton gestational age at delivery was significantly positively correlated with the twin gestational age at delivery (P,.001), and the prior singleton birth weight was significantly positively correlated with the birth weight of the larger twin (P,.001) and the smaller twin (P,.001). The rate of twin preterm birth before 32 weeks of gestation was 3.5% in patients with a prior term birth, 9.2% in nulliparous patients, and 26% in patients with a prior preterm birth (P,.001). The rate of SGA in patients with a prior birth not complicated by SGA was 42.1%, in nulliparous women it was 54.4%, and in patients with a history of SGA it was 65.2% (P5.007). On regression analysis, prior preterm birth and SGA of a singleton pregnancy were independently associated with recurrence of the same condition in a subsequent twin pregnancy. CONCLUSION: Prior preterm birth and SGA in a singleton pregnancy increase the risk of the same condition in a subsequent twin pregnancy. We postulate that the extrinsic mechanism responsible for the pathophysiology of adverse outcomes in twin pregnancies overlaps with that in singleton pregnancies. (Obstet Gynecol 2015;125:870–5)