Abstract:
Links between heat exposure and congenital anomalies have not been explored in detail
despite animal data and other strands of evidence that indicate such links are likely. We reviewed
articles on heat and congenital anomalies from PubMed andWeb of Science, screening 14,880 titles and
abstracts in duplicate for articles on environmental heat exposure during pregnancy and congenital
anomalies. Thirteen studies were included. Most studies were in North America (8) or the Middle East
(3). Methodological diversity was considerable, including in temperature measurement, gestational
windows of exposure, and range of defects studied. Associations were detected between heat
exposure and congenital cardiac anomalies in three of six studies, with point estimates highest
for atrial septal defects. Two studies with null findings used self-reported temperature exposures.
Hypospadias, congenital cataracts, renal agenesis/hypoplasia, spina bifida, and craniofacial defects
were also linked with heat exposure. Effects generally increased with duration and intensity of
heat exposure. However, some neural tube defects, gastroschisis, anopthalmia/microphthalmia
and congenital hypothyroidism were less frequent at higher temperatures. While findings are
heterogenous, the evidence raises important concerns about heat exposure and birth defects. Some
heterogeneity may be explained by biases in reproductive epidemiology. Pooled analyses of heat
impacts using registers of congenital anomalies are a high priority.
