675: Does a history of spontaneous preterm birth (sPTB) of twins increase the risk of subsequent singleton sPTB?

Abstract

It remains a conundrum whether gravidae with a history of a twin sPTB are at significant risk of sPTB in subsequent pregnancies. The aim of this study was to leverage a comprehensive perinatal database to evaluate the impact of prior sPTB of both singletons and twins on subsequent pregnancies. This is a retrospective cohort study utilizing a single center database of deliveries from August 2011 - June 2016. All deliveries were included as index pregnancies, including term and preterm deliveries and singleton and twin gestations. Prior history of singleton or twin sPTB was abstracted from the electronic medical record or solicited directly from subjects. Preterm deliveries were classified as spontaneous in the absence of documented indication for preterm delivery, and suspected indicated PTBs were excluded (e.g., preeclampsia, IUGR, or abnormalities of placentation). Of the 17,256 deliveries that occurred during the study period, 16,605 met inclusion criteria (16,379 singleton and 226 twin deliveries). Of the index singleton pregnancies, 1,083 (6.6%) delivered spontaneously preterm while 131 (58.0%) of index twin pregnancies delivered spontaneously preterm. Consistent with previous literature, women with a history of singleton sPTB were at greater risk for subsequent singleton sPTB (536/1017 (5.3%) vs. 248/1439 (17.2%); OR 3.72, 95% CI 3.16-4.37). Compared to women with a history of twin term birth, women with a history of twin sPTB trended towards but did not have a significant higher likelihood of delivering a subsequent singleton preterm (4/51 (7.8%) vs. 1/106 (0.94%); OR 8.94, 95% CI 0.97-82.17). Compared to women with a history of singleton term birth, women with a history of singleton sPTB were more likely to deliver twins spontaneously preterm (22/29 (75.9%) vs. 69/127 (54.3%); OR 2.64, 95% CI 1.05-6.63). Based on our results, a history of singleton sPTB increases the risk of subsequent twin sPTB. Our study did not show a significant increase in singleton sPTB among women with a history of twin sPTB. We speculate that women with a history of twin sPTB are unlikely to benefit from preterm birth prevention strategies in the setting of subsequent singleton pregnancy while women with a history of singleton sPTB with subsequent twins may benefit from prevention strategies.