- In the project led by Sagi Shashar (Shashar et al, 2020) the investigators explored the link between temperature and preeclampsia. The results indicated that elevated temperature in pregnancies falling on warm seasons were associated with development of preeclampsia (PET). Interestingly, the same elevation in pregnancies during cold seasons, was associated with a decreased risk of PET. The findings suggest that body adjustment to temperature fluctuations might be crucial in our understanding of its effect. In relation to PET, temperature might be associated with perturbations in maternal heat homeostasis that in turn results in reallocation of energy resources and their availability to the fetus, resulting in PET.
Important to note, that this was one of the first studies showing heterogeneity of the two ethnic populations in the Negev, Jewish and Bedouin-Arab, the latter being more exposed and less resilient to adverse ambient exposures as compared to it Jewish neighbors. Most of the differences can be explained by socio-economic discrepancies, resulting in exposure of low-income, usually Bedouin-Arab, populations to hazardous environment of temporary tents and shacks, an absence of less air-conditioning, etc.
- In the project led by Roni Gat (Gat et al, 2021) we analyzed 84,476 deliveries in Soroka between 2003-2013 with an angle at preterm labor and preterm prelabor rupture of membranes (PPROM). While a preterm delivery is a widely-investigated outcome, Gat et al hypothesized that preterm PROM outcome, which is a subset of preterm diagnosis, is supposed to be more sensitive composite for investigation of its link with environment. This is mainly due to the spontaneous nature of prelabor rupture of membranes independent of medical decisions and birth inductive treatments.
Indeed, PPROM was found more sensitive to temperature fluctuations than the general diagnosis of preterm delivery. As in the study by Shashar et al (Shashar et al, 2020) this effect was modified by the ethnicity, whereas Bedouin- Arabs were susceptible to heat few days prior to delivery (Relative Risk (RR)=1.19 per increase in each interquartile range (IQR) unit).
Of note, Jewish population was found more susceptible to pollution, measured in particulate matter (PM) with an effect estimated at RR=1.025 for exposure to one IQR a day prior to delivery.
Similar to the study by Shashar et al (Shashar et al, 2020) , the Bedouin-Arab population living in rural and often temporarily constructed buildings without air-conditioning, were more exposed to the effect of temperature fluctuations. The Jewish population on the other hand, living in mostly urban and industrialized settlements were more resilient to temperature variations, but were probably more exposed to air pollutants such as transport emissions and fuel combustion.
One of the main findings is regarding the exposure window period relevant for investigation of temperature and birth onset. The effect was more pronounced for exposures measured up to one week prior to delivery, pointing at the short-term effect of heat rather than with other outcomes, like PET of birth weight, where a longer cumulative exposure is more relevant.
- The findings by Shashar et al were recently confirmed by an investigation led by Yaroslav Yousim. The researchers explored the Soroka historical cohort of 129,009 pregnancies, using a more advanced statistical methodology. They reported a positive association between temperature and preeclampsia during gestation, especially during 1st and 3rd trimester (Youssim et al, 2023).