Ambient temperature and ovarian hyperstimulation syndrome: An observational study

To evaluate the association between ambient temperature and ovarian hyperstimulation syndrome (OHSS).

This retrospective cohort study included 28 397 women aged 40 years and younger who underwent oocyte retrieval at a tertiary hospital between January 2018 and December 2023. Women were grouped according to their average ambient temperatures 7 days after oocyte retrieval. The main outcome was severe to critical OHSS, and the secondary outcome was live birth rate.

Of the 28 397 patients, 23 916 women (84.24%) experienced no OHSS or mild OHSS, 4250 women (17.77%) experienced moderate OHSS, and 231 women (0.97%) experienced severe to critical OHSS. Their average ambient temperatures were 15.27 ± 9.19°C, 15.83 ± 9.22°C, and 17.39 ± 8.88°C, respectively. The incidence rates of severe to critical OHSS were 0.61%, 0.72%, and 1.02% at ambient temperatures <10°C, between 10°C and 20°C, and >20°C, respectively. Using a two-piecewise linear regression model, the ambient temperature inflection point was calculated to be 22.1°C. The risk of severe to critical OHSS increased with ambient temperature until the turning point of 22.1°C (odds ratio, 1.11 [95% confidence interval, 1.00-1.22]; P = 0.043). The increase in average ambient temperature was significantly associated with the incidence of severe to critical OHSS (adjusted odds ratio, 1.025 [95% confidence interval, 1.01-1.04]; P = 0.001). There was no significant association between ambient temperature and live birth rate.

Elevated ambient temperature after oocyte retrieval was associated with an increased risk of severe to critical OHSS. Physicians should be aware of OHSS in women who undergo oocyte retrieval on hot days.