Objective: The objective of this study is to determine whether a single episode of vaginal bleeding occurring between 24 and 34 weeks gestation is associated with preterm delivery and other adverse maternal and neonatal outcomes.Study design: We conducted a retrospective cohort study in the Maternal-Fetal unit of two campuses of a large tertiary, medical center with approximately 12,000 deliveries annually. The study group consisted of all women with a singleton pregnancy between 24 + 0/7 and 33 + 6/7 weeks of gestation, admitted to the high-risk antenatal ward due to a single episode of vaginal bleeding of unknown origin between May 2003 and December 2014. Maternal and neonatal parameters of the study group were compared to the maternal and neonatal parameters of the rest of the singleton deliveries occurring in our institution during the study period. The primary outcome was rate of preterm delivery while secondary outcomes were other adverse maternal and neonatal outcomes. Multivariate logistic regression was performed to identify risk factors for preterm delivery in the study group.Results: Two hundred thirty women met the inclusion criteria and 51,468 women were in the comparison group. Preterm delivery rates were 20% and 5.5% in the study and the comparison group, respectively OR = 3.55 [2.63-4.78] (p < .001). The aOR for preterm delivery among the study group for women with a previous preterm delivery was 4.62 [1.17-18.20] (p = .029) and for women with a short cervix was 9.35 [2.30-37.95] (p = .002).Conclusions: A single episode of third-trimester vaginal bleeding is an independent risk factor for spontaneous preterm delivery. The presence of a shortened cervix or a history of a prior spontaneous preterm delivery increases this risk significantly.Key messageThird trimester vaginal bleeding is strongly associated with preterm delivery. Knowledge of this relationship has valuable clinical implications for practicing obstetricians.
Keywords: Third-trimester vaginal bleeding; high-risk pregnancy; placental abruption; preterm delivery; vaginal bleeding.