Some lower genital tract infections are associated with an increased likelihood of adverse birth outcomes, according to a study of women attending public STD clinics.1 Women who received a diagnosis of gonorrhea had increased odds of having a preterm birth (odds ratio, 2.0), while those with a chlamydia diagnosis had heightened chances of delivering a low-birth-weight infant (2.1). The odds of experiencing either adverse outcome were lower among women who initiated antenatal care and visited an STD clinic in the same trimester than among those who made no antenatal visits (0.4).

The case-control study used the electronic medical records of pregnant women aged 13–49 who visited public STD clinics in Baltimore between 1996 and 2002. Clinic records, containing information on demographic characteristics, STD history and symptoms, risk behaviors, physical examination results and laboratory results, were matched with state vital statistics records for births within 12 months of the clinic visit. The study sample was made up of the 730 women who had had one live singleton birth in the study period and for whom complete data on term and birth weight were available. Women were categorized according to whether they experienced no adverse birth outcome, a preterm birth (defined as one occurring before 37 weeks’ gestational age) or delivery of a low-birth-weight infant (defined as one weighing less than 2,500 g).

Women included in the study were primarily black, younger than 25 and in their first trimester of pregnancy when they attended the STD clinic. Among women who experienced an adverse birth outcome, the mean age at clinic visit was 24.2; among controls, it was 21.7. Overall, half of women visited a clinic because of STD symptoms, four in 10 reported recent alcohol or illicit drug use, four in 10 had used contraceptives in the previous 30 days and one in 10 had had more than two sex partners in that same period. Nearly half of women had not known they were pregnant before visiting the STD clinic. The prevalence of lower genital tract infections was high: Some 30% of women had bacterial vaginosis, 15% trichomoniasis, 14% chlamydia, 7% gonorrhea and 18% multiple infections. Nineteen percent of women gave birth to a preterm infant, and 16% delivered low-birth-weight newborns.

In a multivariate analysis that controlled for a range of potential predictors of adverse birth outcomes, gonorrhea was the only lower genital tract infection associated with an increased risk for preterm birth (odds ratio, 2.0). The association was stronger among women who received their diagnosis in the first trimester than among those whose infection was discovered later (3.0). Chlamydia was associated with low birth weight (2.1), especially when the analysis was restricted to women who delivered a low-birth-weight infant at term (indicating intrauterine growth restriction—4.6).

The odds of delivering a preterm or low-birth-weight infant rose with women’s age (odds ratio, 1.1 for each outcome), and both adverse outcomes were positively associated with having a disease that complicated the pregnancy (2.3 and 2.0, respectively) and having had a previous preterm birth (16.4 and 16.7). Having had 12 or fewer years of education was a risk factor for preterm birth (3.8).

Adverse birth outcomes were more common among women who received no antenatal care than among those who received any (odds ratios, 2.6–2.7), and each additional antenatal visit was associated with a 10% reduction in the odds of delivering a preterm or low-birth-weight infant. The odds of experiencing an adverse birth outcome were lower among women who initiated antenatal care and visited an STD clinic in the same trimester than among those who made no antenatal visits or for whom data on antenatal care were missing (0.4). Recent cocaine and alcohol use was associated with increased odds of experiencing adverse outcomes (1.6–4.3), but these associations lost significance in analyses adjusting for lower genital tract infection.

The researchers acknowledge that the power of their study may have been reduced by the unavailability of matched records for many women, and that data on STD diagnoses could be incomplete, as they were based on only one clinic visit. However, they point out that variation in the associations between lower genital tract infections and adverse birth outcomes according to timing of diagnosis and care indicate a need for improved services for high-risk pregnant women: “Comprehensive clinic-based interventions targeting pregnant women who seek care at STD clinics, such as enhanced case and partner management, facilitation of communication with the patient’s antenatal care provider, and enrollment in substance abuse treatment programs…may have a significant positive impact on pregnancy outcomes.”—H. Ball