A case-control study of maternal bathing habits and risk for birth defects in offspring

Background: Nearly all women shower or take baths during early pregnancy; however, bathing habits (i.e., shower and bath length and frequency) may be related to the risk of maternal hyperthermia and exposure to water disinfection byproducts, both of which are suspected to increase risk for multiple types of birth defects. Thus, we assessed the relationships between bathing habits during pregnancy and the risk for several nonsyndromic birth defects in offspring. Methods: Data for cases with one of 13 types of birth defects and controls from the National Birth Defects Prevention Study delivered during 2000-2007 were evaluated. Logistic regression analyses were conducted separately for each type of birth defect. Results: There were few associations between shower frequency or bath frequency or length and risk for birth defects in offspring. The risk for gastroschisis in offspring was increased among women who reported showers lasting >= 15 compared to <15 minutes (adjusted odds ratio: 1.43, 95% confidence interval: 1.18-1.72). In addition, we observed modest increases in the risk for spina bifida, cleft lip with or without cleft palate, and limb reduction defects in offspring of women who showered >= 15 compared to < 15 minutes. The results of comparisons among more specific categories of shower length (i.e., < 15 minutes versus 15-19, 20-29, and >= 30 minutes) were similar. Conclusions: Our findings suggest that shower length may be associated with gastroschisis, but the modest associations with other birth defects were not supported by analyses of bath length or bath or shower frequency. Given that showering for >= 15 minutes during pregnancy is very common, further evaluation of the relationship between maternal showering habits and birth defects in offspring is worthwhile.