Objective To examine the effect of first and/or second trimester vaginal bleeding on pregnancy outcome.
Design A prospective one-year birth cohort.
Setting Two northernmost administrative districts of Finland.
Patients 8718 singleton pregnancies, of whom 807 (9.3%) reported bleeding during the first (601) and/or second trimester (206); light bleeding in 595 cases and heavy bleeding in 212. The remaining 7911 women served as a reference group.
Main outcome measures Low birth weight rate (LEW), preterm birth rate, congenital malformations and perinatal mortality rate.
Results Bleeding was most frequent in women of more advanced age (≥35 years old), with previous miscarriages, with infertility problems or using an IUCD prior to the pregnancy. Parity, smoking and social status were not associated with bleeding. Caesarean section rate and placental complications during the third trimester and at delivery were more common among the bleeders than in the reference group. The LBW rate was three-fold among the bleeders and the preterm birth rate twofold. The risk (OR) of a LBW infant among second trimester bleeders was 4.1 (95% CI 2.6–6.4), that of preterm birth 2.9 (95% CI 1.9–4.6), and that of congenital malformations 2.9 (95 % CI 1.7-4.7). No association existed between bleeding and perinatal mortality.
Conclusions Bleeding during the second trimester indicates a poor pregnancy outcome and an increased risk of LBW, and preterm birth and/or congenital malformation.