Heat and Cold Exposure in Newborn Girls Associated With Lung Function Changes

In female newborns, prenatal/postnatal exposure to heat and cold may be associated with lung function changes, including decreased functional residual capacity (FRC), increased respiratory rate (RR), and lower tidal volume, according to study findings published in Journal of the American Medical Association Network Open.

Extreme temperature changes are known to stress both pregnant mothers and newborns. With climate change a growing concern, researchers sought to assess the association of prenatal and postnatal heat or cold exposure on lung function in newborns and to determine when such exposure could have a critical affect.

The researchers conducted a population-based cohort study, analyzing data from 343 mother-newborn pairs (median maternal age at conception 32 years; 53% male newborns) recruited between July 2014 and July 2017 in the French Grenoble metropolitan area. Among those 343 mother-newborns pairs, 251 newborns had not been exposed to tobacco; 218 had parental rhinitis; there were 291 vaginal births; 297 newborns were breastfeeding at 2 months; 193 newborns had at least 1 sibling; and for 246 pairs, the mother and/or fathers held a master’s degree or above.

Minimum, maximum, mean, and standard deviation temperatures at the mother-child’s residence were estimated using a spatiotemporally resolved model. Distributed lag nonlinear models were used to analyze adjusted associations between newborn lung function and long-term (35 gestational weeks and the first 4 weeks after birth) and short-term (7 days before lung function test) exposure to ambient temperature. Lung function (RR, tidal volume, mean minute ventilation, and time to peak tidal expiratory flow to total expiratory time ratio) was evaluated in newborns (median age, 6.7 weeks) by recording 10 minutes of tidal breathing in the sleeping child. Analyses were adjusted for numerous potential confounders.

Researchers noted temperature exposure was similar across sex with the highest temperatures in July (22.8°C), lowest in January (3.0°C), and median overall temperature during pregnancy 12.7°C (IQR, 10.5°C-14.5°C).

Male newborns had a significant association between short-term exposure to overall and daytime heat the last 2 to 4 days before the lung function test (and reduced FRC was identified). Overall, however, there were no other consistent associations observed for male newborns.

Among female newborns, researchers found long-term heat exposure (95^th vs 50^th percentile of mean temperature) was associated with decreased functional residual capacity (-39.7 mL; 95% CI, -68.6 mL to -10.7 mL for 24°C vs 12°C at gestational weeks 20-35 and weeks 0-4 after delivery) and with increased RR (28.0/min; 95% CI, 4.2-51.9/min for 24°C vs 12°C at gestational weeks 14-35 and weeks 0-1 after delivery).

Among female newborns, researchers found long-term cold exposure (5^th vs 50^th percentile of mean temperature) associated with lower functional residual capacity

(-21.9 mL; 95% CI, -42.4 mL to -1.3 mL for 1°C vs 12°C at gestational weeks 15-29), lower tidal volume (-23.8 mL; 95% CI, -43.1 to -4.4 mL for 1°C vs 12°C at gestational weeks 14-35 and weeks 0-4 after birth), and increased RR (45.5/min; 95% CI, 10.1-81.0/min for 1°C vs 12°C at gestational weeks 6-35 and weeks 0-1 after birth).

Study limitations include the use of a relatively small and well-educated population sample, which limits the study’s generalizability, and potential false associations due to numerous statistical tests.

“In a temperate climate, prenatal and postnatal exposure to heat and cold was associated with lung function changes (decreased FRC and increased RR) in female newborns,” researchers concluded. They further concluded cold was associated with lower tidal volume in girl newborns. They added “Critical windows of susceptibility ranged from the second trimester of pregnancy until the fourth week of life.”

Disclosure: 1 study author declared affiliations with biotech, pharmaceutical, and/or device companies. Please see the original reference for a full list of authors’ disclosures.