713: Does a single episode of third trimester bleeding really matter?

The aim of this study was to determine whether a single episode of uterine bleeding between 24 and 34 weeks of gestation is associated with spontaneous preterm delivery. We conducted a retrospective cohort study in the maternal fetal unit of two campuses of a tertiary care center university teaching hospital with approximately 10,000 deliveries per year. The study group consisted of all women with singleton pregnancy between 24+0/7 and 34+0/7 weeks of gestation admitted to the high-risk antenatal ward due to a single episode of uterine bleeding between 2003 and 2014. We excluded women with bleeding placenta previa and those with clinically evident abruption necessitating immediate delivery. Maternal and neonatal parameters were compared to the data of singleton deliveries in our institution between 2010-2015 (N=51,468). Multivariate logistic regression was performed to identify risk factors for preterm delivery in the study group. Two hundred and thirty women met the inclusion criteria while 50,468 women with singleton deliveries served as a control group. Preterm delivery rates were 20% and 5.5% in the study and the control group, respectively (P-value<0.001) (Figure 1). Demographic and obstetric characteristics of the groups are summarized in Table 1. The adjusted Odds Ratio (aOR 95%CI) for preterm delivery among the study group was 4.62 [1.17-18.20] (P=0.029) for women with previous preterm delivery and 9.35 [2.30-37.95] (P=0.002) for women with short cervix. Even without these known risk factors the OR for preterm delivery was 3.55 [2.63-4.78] (P<0.001) in comparison to our general popularion. These findings suggest that even a single episode of third trimester uterine bleeding with no other known risk factors is strongly associated with spontaneous preterm delivery. The presence of other risk factors increases the risk significantly. These women should be treated accordingly. Prior to 34 weeks antenatal corticosteroids should be considered and high risk follow up may be advised.