Temperature and Term Low Birth Weight in California

Abstract

Few investigations have explored temperature and birth outcomes. In a retrospective cohort study, we examined apparent temperature, a combination of temperature and relative humidity, and term low birth weight (LBW) among 43,629 full-term LBW infants and 2,032,601 normal-weight infants in California (1999-2013). The California Department of Public Health provided birth certificate data, while meteorological data came from the California Irrigation Management Information System, US Environmental Protection Agency, and National Centers for Environmental Information. After considering several temperature metrics, we observed the best model fit for term LBW over the full gestation (per 10-degrees-Fahrenheit (°F) increase in apparent temperature, 13.0% change, 95% confidence interval: 4.1, 22.7) above 55°F, and the greatest association was for third-trimester exposure above 60°F (15.8%, 95% confidence interval: 5.0, 27.6). Apparent temperature during the first month of pregnancy exhibited no significant risk, while the first trimester had a significantly negative association, and second trimester, last month, and last 2 weeks had slightly increased risks. Mothers who were black or older, delivered male infants, or gave birth during the warm season had infants at the highest risks. This study provides further evidence for adverse birth outcomes from heat exposure for vulnerable subgroups of pregnant women.

Associations between high temperatures in pregnancy and risk of preterm birth, low birth weight, and stillbirths: systematic review and meta-analysis

“…Of the 19 studies reporting birth weight as a continuous variable, 12 noted decreases in birth weight at higher temperatures, including two where the direction of effect varied by trimester (supplementary figure 7b), 79 80 three studies had non-significant findings, and four noted that weight increased at higher temperatures. Generally, the impacts of temperature on weight were small, with most studies reporting changes of under 10 g per change in degree, or under 20 g when comparing high and low temperatures (supplementary table 2b, supplementary fig 4).…”

Temperature and self-reported mental health in the United States

“…Heat stress triggers physiological responses in human bodies, from early signs of heat rash and muscle cramps to impacts on the central nervous system, circulatory system, and broad impacts on many organ systems [3,4]. High temperatures have been associated to negative birth outcomes [5,6], and to increased heat-related mortality, which would have been larger in the absence of air conditioning [7][8][9].…”

Changing trends of birth weight with maternal age: a cross-sectional study in Xi'an city of Northwestern China

“…The curve was the same as the previous study [14,24]. As LBW infants may be premature with other risk factors [25], we restricted our study population to term infants. The etiology of LBW was intrauterine growth restriction [18].…”