Temperature and preeclampsia: Epidemiological evidence that perturbation in maternal heat homeostasis affects pregnancy outcome

Abstract

Introduction: This study aims to determine the association between temperature and preeclampsia and whether it is affected by seasonality and rural/urban lifestyle.

Methods: This cohort study included women who delivered at our medical center from 2004 to 2013 (31,101 women, 64,566 deliveries). Temperature values were obtained from a spatiotemporally resolved estimation model performing predictions at a 1×1km spatial resolution. In "Warm" pregnancies >50% of gestation occurred during the spring-summer period. In cold pregnancies >50% of gestation occurred during the fall and winter. Generalized estimating equation multivariable models were used to estimate the association between temperature and incidence of preeclampsia.

Results: 1) The incidence of preeclampsia in at least one pregnancy was 7% (2173/64,566); 2) during "warm" pregnancies, an elevation of one IQR of the average temperature in the 1st or the 3rd trimesters was associated with an increased risk to develop preeclampsia [patients with Jewish ethnicity: 1st trimester: relative risk (RR) of 2.38(95%CI 1.50; 3.80), 3rd trimester 1.94(95%CI 1.34;2.81); Bedouins: 1st trimester: RR = 2.91(95%CI 1.98;4.28), 3rd trimester: RR = 2.37(95%CI 1.75;3.20)]; 3) In "cold" pregnancies, an elevation of one IQR of average temperature was associated with a lower risk to develop preeclampsia among patients with Bedouin-Arab ethnicity RR = 0.68 (95% CI 0.49-0.94) for 1st trimester and RR = 0.62 (95% CI 0.44-0.87) for 3rd trimester.

Conclusions: 1) Elevated averaged temperature during the 1st or 3rd trimesters in "warm" pregnancies confer an increased risk for the development of preeclampsia, especially in nomadic patients; 2) Of interest, during cold pregnancies, elevated averaged temperature was associated with a lower risk to develop preeclampsia for nomadic patients. 3) These findings suggest temperature might be associated with perturbations in maternal heat homeostasis resulting in reallocation of energy resources and their availability to the fetus that may increase the risk for preeclampsia. This observation is especially relevant in the context of global warming and its effects on maternal/fetal reproductive health.

Fig 1. A Preeclampsia Prevalence and Trimester Averaged Temperature in “Warm” vs. “Cold” Pregnancies, 1^st Trimester.

The LOESS curves of the percent of preeclampsia pregnancies as a function of averaged daily temperatures, out of the “warm” pregnancies vs. the “cold” pregnancies. For instance, out of all women exposed to an average daily temperature of 15° in “cold” pregnancies, approximately +3% were diagnosed with preeclampsia. B Preeclampsia Prevalence and Trimester Averaged Temperature in “Warm” vs. “Cold” Pregnancies, 2^nd Trimester. The LOESS curves of the percent of preeclampsia pregnancies as a function of averaged daily temperatures, out of the “warm” pregnancies vs. the “cold” pregnancies. For instance, out of all women exposed to an average daily temperature of 15° in “warm” pregnancies, approximately +4% were diagnosed with preeclampsia. C Preeclampsia Prevalence and Trimester Averaged Temperature in “Warm” vs. “Cold” Pregnancies, 3^rd Trimester. The show the LOESS curves of the percent of preeclampsia pregnancies as a function of averaged daily temperatures, out of the “warm” pregnancies vs. the “cold” pregnancies. For instance, out of all women exposed to an average daily temperature of 15° in “warm” pregnancies, approximately 4% were diagnosed with preeclampsia.

Fig 2. Association between temperature and preeclampsia for “warm” and “cold” pregnancies; multivariable regression models.

The association between the trimester-specific temperature and preeclampsia by Jewish and Bedouin-Arab ethnicity, in "warm" and "cold" pregnancies. The Y axis represents the RR of the multivariable models, and the X axis the trimesters. The models included averaged temperatures for each trimester in IQR units as the primary exposure at study and were adjusted to maternal age, gravidity, multiple delivery and a history of preeclampsia in the past deliveries. Results in the tables are presented by the relative risks (RR), their 95% confidence intervals (CI) and p-values.