Threatened miscarriage as a predictor of obstetric outcome.

OBJECTIVE: To investigate prospectively the risk of adverse pregnancy outcome in women presenting with first-trimester threatened miscarriage.

METHODS: A prospective cohort study was performed on 214 women presenting with bleeding in the first trimester and 214 asymptomatic age-matched controls. Main outcome measures included gestational age and weight at delivery and incidence of adverse pregnancy outcome.

RESULTS: The first-trimester miscarriage rate, after confirmation of viability in the threatened miscarriage group, was 9.3%. Compared with controls, women presenting with threatened miscarriage were more likely to deliver prematurely, 5.6% compared with 11.9%, respectively, (relative risk 2.29, 95% confidence interval 1.4-4.6), and this was most likely to be between 34 and 37 weeks. They were also more likely to have preterm prelabor rupture of membranes, 1.9% compared with 7%, respectively, (relative risk 3.72, 95% confidence interval 1.2-11.2). Overall, there was no difference in mean birth weight and in the incidence of other obstetric complications between the 2 groups; however, women in the threatened miscarriage group were more likely to deliver neonates between 1,501 g and 2,000 g (P = .04).

CONCLUSION: Women with threatened miscarriage in the first trimester are at increased risk of premature delivery, and this risk factor should be taken into consideration when deciding upon antenatal surveillance and management of their pregnancies.

LEVEL OF EVIDENCE: II-0.