Ambient temperature, heat exposure and diminished ovarian reserve among women undergoing assisted reproductive technologies

Association between heat exposure and diminished ovarian reserve (DOR) among women undergoing assisted reproductive technologies remains underexplored. We conducted a retrospective cohort study of 4296 women from a reproductive medicine center in Wuhan, China. Ambient temperature exposures were estimated based on the women's residential address and then averaged over short-term (1 month, 3 months, and 6 months) and long-term (1 year, 2 years, and 3 years) exposure windows. Heatwave exposure was defined using absolute (≥ 35°C) and relative (90th/95th percentiles) temperature thresholds over consecutive days (D2: >2 days; D3: >3 days), and was further categorized into high exposure (above median), low exposure (median and below) and no exposure. Multivariable logistic regression models were used to estimate odds ratios (ORs) for DOR (Anti-Müllerian hormone [AMH] < 1.1 ng/mL). Each standard deviation (SD) increase in mean, maximum, and apparent temperature over a 1-month period was associated with a 37 % (2 %-83 %), 36 % (2 %-80 %), and 55 % (4 %-131 %) higher odds of DOR. Compared to no exposure, 1-year heatwave exposure (35°C-D3) was associated with a 64 % (5 %-156 %) higher odds of DOR. Low-frequency heatwave exposure over 1 year (90th-D3: OR=1.33 [1.02-1.74]) and 3 years (95th-D2: OR=1.41 [1.08-1.70]) also showed significant associations, while high-frequency heat exposure did not exhibit such effects. Similarly, low-duration heatwave exposure over the 3-year period was associated with higher DOR risk. Higher temperatures and heatwaves exposure were associated with higher risk of DOR. Highlighting the needs to both short-term temperature variability and prolonged low-frequency heatwaves, rather than focusing solely on extreme high-intensity events.