Genital flora in pregnancy and its association with intrauterine growth retardation

A study of risk factors for intrauterine growth retardation (IUGR) was conducted among a cohort of 13,914 pregnant women enrolled in the multicenter Vaginal Infections and Prematurity Study. From 23 through 26 weeks of gestational age, cultures of specimens from the vagina and cervix were done for group B streptococci, Neisseria gonorrhoeae, Chlamydia trachomatis, Trichomonas vaginalis, Candida albicans, Gardnerella vaginalis, Mycoplasma hominis, Ureaplasma urealyticum, and anaerobic gram-negative rods belonging to the genera Bacteroides, Porphyromonas, and Prevotella. Newborns who were small for their gestational age were delivered by 1,251 women, and infants of the appropriate weight for their gestational age were delivered by 10,332 women. When controlling for ethnicity and smoking and excluding women treated with antibiotics, the Mantel-Haenszel adjusted relative risk of IUGR was 1.16 for Bacteroides, Prevotella, and Porphyromonas spp. (95% confidence interval [95% CI], 1.01 to 1.33), 1.16 for M. hominis (95% CI, 1.04 to 1.29), 1.20 for U. urealyticum (95% CI, 1.05 to 1.38), and 1.22 for T. vaginalis (95% CI, 1.05 to 1.42). There was also a strong and significant trend for an increasing risk of IUGR with the number of these four microbes recovered. Among women colonized with all four isolates, the adjusted odds ratio of IUGR was 1.79 (95% CI, 1.27 to 2.52) in comparison with women not colonized with any of these microorganisms. Group B streptococci, N. gonorrhoeae, C. trachomatis, and C. albicans were not significantly associated with IUGR. These results suggest that infection is associated with some cases of IUGR and that specific microorganisms, alone or in combination, are involved. Since genital isolates are highly correlated with each other, the relative contribution of each microbe is difficult to determine.