Exposure to suboptimal ambient temperature during specific gestational periods and adverse outcomes in mice

Abstract

Exposure to suboptimal ambient temperature during pregnancy has been reported as a potential teratogen of fetal development. However, limited animal evidence is available regarding the impact of extreme temperatures on maternal pregnancy and the subsequent adverse pregnancy outcomes. Our objective in this study is to investigate the relationship between temperature and maternal stress during pregnancy in mice. This study used the Naval Medical Research Institute (NMRI) mice during the second and third pregnant weeks with the gestational day (GD) (GD 6.5-14.5 and GD 14.5-17.5). Mice were exposed to suboptimal ambient temperature (1°C, 5°C, 10°C, 15°C, 40°C, 42°C, 44°C, 46°C, and 48°C for the experimental group and 23°C for the control group) 1 h per day, 7 days a weekin each trimester. Measurements of placental development (placental weight [PW] and placental diameter [PD]) and fetal growth (fetal weight [FW] and crown-to-rump length [CRL]) between experimental and control groups were compared using analysis of variance (ANOVA). Data on the occurrence of preterm birth (PTB) and abnormalities were also collected. The results showed that exposure to both cold and heat stress in the second and third weeks of pregnancy caused significant decreases in measurements of placental development (PW and PD) and fetal growth (FW and CRL). For all temperature exposures, 15°C was identified as the optimal temperature in the development of the embryo. Most PTB occurrences were observed in high-temperature stress groups, with the highest PTB number seen in the exposure group at 48°C, whereas PTB occurred only at 1°C among cold stress groups. In the selected exposure experiments, an approximate Ushaped relation was observed between temperature and number of abnormality occurrence. The highest percentage of these anomalies occurred at temperatures of 1°C and 48°C, while no abnormalities were observed at 15°C and in the control group. Our findings strengthened the evidence that exposure to suboptimal ambient temperatures may trigger adverse pregnancy outcomes and worsen embryo and fetal development in mice.

Association between low ambient temperature during pregnancy and adverse birth outcomes: a systematic review and meta-analysis

“…This is similar to other studies which reported environmental factors such as air pollution exposure during the late pregnancy is more likely to cause LBW compared with other trimesters [55] . This may be due to fact that the last trimester is a period of accelerated fetal and placental growth [56,57] . Different from the increased risk of LBW, we found that the risk of SGA was not increased when exposed to extremely low ambient temperature.…”

Contribution of prenatal exposure to ambient temperature extremes and severe maternal morbidity: A retrospective Southern birth cohort

“…In fact, one study showed that prenatal exposure to 18°C in mice initiated fetal fat brown fat storage; whereby, cold temperatures experienced during the third trimester may initiate cold-stress-related changes in the placenta (50). Cold stress in mice during the prenatal period has also been associated with negative impacts on a number of neuroimmune pathways, particularly as it pertains to the maternal hippocampus (51) and placental changes following late in pregnancy exposure (52). Vasoconstriction in the winter months has been identified as one possible explanation (53), while others have proposed environmental exposures encountered in the month of conception as important determinants for eclampsia onset (54).…”

The Association of Ambient Temperature with Extremely Preterm Births

“…Animal studies have found that elevated maternal temperatures adversely affect vital developmental processes, such as cellular development and central nervous system development, and has been linked to spontaneous abortions (Edwards, 1986;Edwards et al, 2003). A study of pregnant mice showed that placental weight and diameter decreased at both higher and lower temperature exposures (Mayvaneh et al, 2020). Exposure to cold temperatures induces peripheral vasoconstriction, which has been hypothesised to alter blood flow to the placenta (Van Zutphen et al, 2014).…”