Maternal and Child Health Library

MCH Alert: Focus on Infant Mortality is developed by the Maternal and Child Health Library in collaboration with the National Sudden Infant Death Resource Center. This and past issues are available online at http://www.mchlibrary.info/alert/archives.html and http://www.sidscenter.org/alert/archives.html.

February 29, 2008

1. REVIEW EXAMINES SCREENING FOR BACTERIAL VAGINOSIS IN PREGNANCY

"New treatment trial data pooled with 2001 report data showed no benefit to screening and treating women who are asymptomatic for bacterial vaginosis if they had a low or average risk for preterm delivery for the outcomes of delivery before 37, 34, or 32 weeks; preterm, premature rupture of membranes; or low birthweight," state the authors of an article published in the February 5, 2008, issue of the Annals of Internal Medicine. Preterm birth rates have increased in the past decade, and strong epidemiologic evidence has suggested an association between bacterial vaginosis and preterm birth. After decades of research and with heightened awareness of measuring potential adverse effects of medications, evidence is emerging that the drug being used to treat bacterial vaginosis may, at some doses and for some populations, be triggering adverse pregnancy outcomes. At the same time, evidence suggests that inherent differences in populations, such as previous pregnancy complications, gestational age, ethnicity, or co-infection, may also influence which women are helped or harmed by screening and treatment for bacterial vaginosis. This review was conducted for the U.S. Preventive Services Task Force (USPSTF) to update its 2001 recommendations by examining the evidence on the value of screening for and treating bacterial vaginosis in reducing adverse pregnancy outcomes for asymptomatic women at low, average, and high risk for preterm delivery.

Relevant studies were identified from searches of Cochrane databases, Ovid MEDLINE, reference lists of other systematic reviews, individuals studies, editorials, reports, and Web sites and by consulting experts. Selected studies included systematic reviews and individual randomized, controlled trials that evaluated screening, treatment, pregnancy outcomes, or adverse effects for asymptomatic women with bacterial vaginosis. Data on the studies' design, sample, setting, demographic characteristics, inclusion and exclusion criteria, diagnostic methods, and risk factors were extracted. Pregnancy outcome data were also abstracted. Relevance and internal validity were evaluated using pre-defined study-quality criteria and rating systems. The researchers performed a series of meta-analyses that included new studies identified from the search, as well as from studies identified from the previous review, to estimate the effect of treatment on preterm delivery (less than 37 weeks, less than 34 weeks, or less than 32 weeks); low birthweight; and preterm, premature rupture of membranes.

The authors found that

• There were no studies that compared pregnancy outcomes for women who are asymptomatic for bacterial vaginosis in a screened population vs. a non-screened population.
• Seven new randomized, controlled trials were included in the area of treatment of asymptomatic pregnant women with bacterial vaginosis.
• There was substantial heterogeneity among trials of treatment in the high-risk group; projections suggest that although a subgroup of high-risk women may benefit from screening and treatment for bacterial vaginosis in pregnancy, a sizeable group would receive no benefit or might experience harm.
  

"Studies to date of bacterial vaginosis in asymptomatic pregnant women have not provided sufficient numbers or details to identify the specific factors playing the most prominent role for harms or benefits," state the authors. They conclude that "more research is needed to better understand these groups and the conditions under which treatment can be harmful or helpful and to explore relevance to other adverse pregnancy outcomes, including preterm delivery before 34 weeks."

Nygren P, Rongwel F, Freeman M, et al. 2008. Evidence on the benefits and harms of screening and treating pregnant women who are asymptomatic for bacterial vaginosis: An update review for the U.S. Preventive Services Task Force. Annals of Internal Medicine 148(3):220-233. Available at http://www.ahrq.gov/clinic/uspstf08/bv/bvup.pdf.

Readers: The U.S. Preventive Services Task Force Summary of Recommendations and supporting documents are available at http://www.ahrq.gov/clinic/uspstf/uspsbvag.htm.

• SGA status at birth was normal in infants with an ALTE but elevated in those who died of SIDS.
• Fewer CHIME infants with an ALTE were low birthweight, compared with those who died of SIDS.
• The age distribution of ALTE mothers corresponded to the ages of mothers within the general population, whereas SIDS mothers were disproportionately younger.
• ALTE peaked during the first 2 months of life, whereas SIDS peaked at between 2 and 4 months.

• Housing instability: 48%.
• Food insecurity: 32%.
• Lack of social support: 75%.
• Intimate partner violence: 7%.
• Other physical/sexual abuse: 9%.
• Depression: 18%.
• Cigarette use: 23%.
• Alcohol use: 23%.
• Drug use: 25%.

• Overall, 22% of the late-preterm infants and 3.0% of the term infants had morbidity during their birth hospitalization.
• Morbidity rates approximately double for each additional gestational week earlier than 38 weeks, from 5.9% morbidity at 37 weeks to 51.7% at 34 weeks.
• The risk for newborn morbidity was greater than additive when both risk factors (being born preterm and being born to a mother with one of the eight selected maternal medical conditions) were present compared with when neither was present.
• Later-preterm infants with mothers who had antepartum hemorrhage and HDP had the highest risks for newborn morbidity.