XXXX or Small for Gestational Age in a Singleton Pregnancy and Risk of Recurrence in a Subsequent Twin Pregnancy.

@entity1 @entity600
OBJECTIVE: To evaluate whether a history of @entity600 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. @entity1 with a history of singleton @entity600 at less than 37 weeks of gestation were compared with @entity1 with a history of singleton term birth and nulliparous @entity1 . 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 @entity600 before 32 weeks of gestation was 3.5% in @entity1 with a prior term birth, 9.2% in nulliparous @entity1 , and 26% in @entity1 with a prior @entity600 (P<.001). The rate of SGA in @entity1 with a prior birth not complicated by SGA was 42.1%, in nulliparous @entity1 it was 54.4%, and in @entity1 with a history of SGA it was 65.2% (P=.007). On regression analysis, prior @entity600 and SGA of a singleton pregnancy were independently associated with recurrence of the same condition in a subsequent twin pregnancy. CONCLUSION: Prior @entity600 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. LEVEL OF EVIDENCE: II.
