Maternal use of hot tub and major structural birth defects§


  • Presented at the annual working meeting of the Texas Center for Birth Defects Research and Prevention, on August 10, 2010, at The University of Texas, Houston Health Science Center, Medical School, Houston, Texas.

  • Supported by the Texas Center for Birth Defects Research and Prevention by a Cooperative Agreement with the Centers for Disease Control and Prevention (grant number U50/CCU613232, PA 02081), and a grant from the Vietnam Education Foundation.

  • §

    The opinions, findings, and conclusions stated herein are those of the authors and do not necessarily reflect those of Vietnam Education Foundation.



Previous studies on the associations between hot tub use during early pregnancy and birth defects have found an increased risk of neural tube defects, but no increase in risk of cardiac defects. No previous studies have assessed the association between maternal hot tub use and other types of noncardiac birth defects.


We included mothers of infants with birth defects (n = 10,825) and mothers of infants without birth defects (n = 6795) who participated in the multisite National Birth Defects Prevention Study between 1997 and 2005. Odds ratios were adjusted for maternal ethnicity and education.


Analysis of 17 birth defects revealed that mothers of infants with gastroschisis and anencephaly were significantly more likely to report any use of a hot tub in early pregnancy: adjusted odd ratios were 1.54 (95% confidence interval [CI], 1.10–2.17) and 1.68 (95% CI, 1.05–2.70), respectively. Among the mothers who reported using a hot tub more than once in the exposure period and remaining in it for more than 30 min, we found significantly elevated odds ratios (≥2.0) for esophageal atresia, omphalocele, and gastroschisis and a nonsignificant elevation (≥2.0) for spina bifida and anencephaly.


These results suggest that women who use hot tubs more than once during early pregnancy and for long periods of time have an increased risk of certain birth defect phenotypes, particularly anencephaly and gastroschisis. Because of multiple statistical tests and small sample sizes, we cannot exclude the possibility that some of these elevated associations may be due to chance. Birth Defects Research (Part A), 2011. © 2011 Wiley-Liss, Inc.