Question: How much does persistent bleeding in first and second trimesters increase the risk of preterm labour/poor obstetric outcome?
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Answer: Three studies have reported the risks of preterm labour or other adverse outcomes after bleeding in both the first and second trimesters:
Hossain et al report a cohort study which included 35 women with vaginal bleeding in both the first and second trimesters. As compared to women with no bleeding, those who bled during the first and second trimesters had a 6.24-fold increased risk of spontaneous preterm labor; and 2-3-fold increased risk of medically induced preterm delivery and preterm premature rupture of membrane, respectively.
Ananth et al analysed data collected from 46,364 singleton births delivered in 1959-1966 in the United States. They found that "Any episode of vaginal bleeding at <20 weeks in pregnancy conferred an increased risk of placental abruption (adjusted relative risk (RR) 1.6, 95% confidence interval (CI) 1.3, 1.8). The greatest risk occurred with bleeding in both the first two trimesters (RR 3.1, 95% CI 2.3, 4.1)."
Yang et al's cohort study included 56 women with bleeding in both trimesters. They found that "Bleeding in both trimesters was associated with preterm birth due to preterm labor (RR = 3.6, 95% CI: 1.9, 6.8). Bleeding of multiple episodes, on multiple days, and with more total blood loss was associated with an approximate twofold increased risk of earlier preterm birth, PPROM, and preterm labor."
As regards persistent bleeding, a prospective study by Mau reports that frequency of bleeding influences the risk of premature delivery. "Every additional bleeding will increase the risk, especially if bleeding occurs in the second trimester. For example the risk of prematurity exceedes 25%, if bleeding occurs four times or more."
(Evidence level IIa)
References:
- Ananth CV. Oyelese Y. Prasad V. Getahun D. Smulian JC. Evidence of placental abruption as a chronic process: associations with vaginal bleeding early in pregnancy and placental lesions. European Journal of Obstetrics, Gynecology, & Reproductive Biology. 128(1-2):15-21, 2006 Sep-Oct. Abstract
- Hossain R. Harris T. Lohsoonthorn V. Williams MA. Risk of preterm delivery in relation to vaginal bleeding in early pregnancy. European Journal of Obstetrics, Gynecology, & Reproductive Biology. 135(2):158-63, 2007 Dec. Abstract
- Mau G. [Risk of prematurity and reported bleeding in pregnancy (author's transl)]. [German] Original Title: Fruhgeburtsrisiko bei rezidivierenden Schwangerschaftsblutungen Zeitschrift fur Geburtshilfe und Perinatologie. 181(1):17-9, 1977 Feb. Abstract
- Yang J. Hartmann KE. Savitz DA. Herring AH. Dole N. Olshan AF. Thorp JM Jr. Vaginal bleeding during pregnancy and preterm birth. American Journal of Epidemiology. 160(2):118-25, 2004 Jul 15. Full text
Search date: May 2011
Classification of evidence levels
Ia Evidence obtained from meta-analysis of randomised controlled trials.
Ib Evidence obtained from at least one randomised controlled trial.
IIa Evidence obtained from at least one well-designed controlled study without randomisation.
IIb Evidence obtained from at least one other type of well-designed quasi-experimental study.
III Evidence obtained from well-designed non-experimental descriptive studies, such as comparative studies, correlation studies and case studies.
IV Evidence obtained from expert committee reports or opinions and/or clinical experience of respected authorities.
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