Cumulative effects of extreme ambient temperatures on placental perfusion and function markers in early pregnancy: Analysis from a birth cohort study.

BACKGROUND: Exposure to suboptimal temperatures during pregnancy has been associated with adverse pregnancy and birth outcomes related to placental development disorders. No prior studies have examined the potential impacts of temperature on placental markers. We conducted an investigation into the cumulative impact of daily ambient temperature on critical clinical placental perfusion and function markers during the placentation period, utilizing data from a prospective birth cohort in Nanjing, China.

METHODS: We collected UtA-PI data and blood samples during the first follow-up (11-13.5 weeks of gestation) and measured PlGF and PAPP-A concentrations in plasma. We estimated individual daily temperature exposure over the 30 days preceding the follow-up and applied a Distributed Lag Nonlinear Model to evaluate its associations with UtA-PI, PlGF, and PAPP-A levels.

RESULTS: We included 3403, 3407, and 3427 women in the UtA-PI, PlGF, and PAPP-A analyses, respectively. Cold exposure was associated with higher UtA-PI measurements, with the strongest estimated percent change being 14.80% (95% CI: 3.32, 27.55). Both cold and heat exposures were associated with decreased PlGF concentrations, with the strongest estimated percent changes being -44.23% (95% CI: 63.28, -15.30) and -48.27% (95% CI: 64.33, -24.98), respectively. Temperature effects on UtA-PI were immediate, whereas changes in PlGF concentrations manifested after a cumulative lag of 24 days.

CONCLUSIONS: Both cold and heat exposures were associated with changes in placental markers, providing new insights into the potential mechanisms connecting ambient temperature to adverse pregnancy and birth outcomes through disorders of placental development.