The effects of daily meteorological perturbation on pregnancy outcome: follow-up of a cohort of young women undergoing IVF treatment

Abstract

BackgroundHuman reproduction follows a seasonal pattern with respect to spontaneous conception, a phenomenon wherein the effect of meteorological fluctuations might not be unique. However, the effect of seasonal variations on patients who underwent in vitro fertilization (IVF) treatment is unclear. We aimed to evaluate the effects of meteorological variation on the pregnancy rate in a cohort undergoing IVF treatment by performing multivariable analyses.MethodsWe conducted a cohort study in a sub-tropical region with prominent seasonal variations (2005–2016). Women aged < 35 years who were treated with a long ovarian stimulation protocol and underwent fresh embryo transfer (ER) were included. Data on gonadotropin administration (CYCL), oocyte retrieval (OR), ER, and pregnancy outcomes were prospectively recorded. For each patient, the daily average of meteorological data (temperature, humidity, sunlight duration, solar radiation) was recorded from the date of CYCL to ER. Multiple logistic regression analysis adjusted for age, fertilization method, year of the cycle, gonadotropin dose, and transferred embryo grade was performed to determine the relationship between the meteorological parameters and clinical pregnancy. Patients with one successful cycle and one failed cycle were subtracted for a case-control subgroup analysis through mixed effect logistics regressions. Time-series analysis of data in the epidemic level was conducted using the distributed lag linear and non-linear models (DLNMs).ResultsThere were 1029 fresh cycles in 860 women (mean age 31.9 ± 2.0 years). Higher mean temperature from CYCL to OR (adjusted odds ratio [aOR] 1.04; 95% confidence interval [CI] 1.01–1.07, P = 0.01) increased the odds of pregnancy, while OR to ER did not show any statistical significance. Compared to that in winter, the odds of becoming pregnant were higher during higher temperature seasons, summer and autumn (aOR 1.47, 95%CI 0.97–2.23, P = 0.07 (marginally significant) and aOR 1.73, 95%CI 1.12–2.68, P = 0.02, respectively). Humidity, sunlight duration, and solar radiation had no effect on the outcome. The subgroup analysis confirmed this finding. The time-series analysis revealed a positive association between temperature and relative risk for pregnancy.ConclusionsIn IVF treatment, the ambient temperature variation alters the pregnancy rates; this aspect must be considered when obtaining patient consent for assisted conception.

Effects of seasonal variations and meteorological factors on IVF pregnancy outcomes: a cohort study from Henan Province, China

“…There are many controversies about whether seasonal variation and environmental factors are related to pregnancy outcomes in women undergoing IVF treatment. The conclusions drawn from this study are in agreement with previous findings [ 11 , 12 ]. A study conducted at the University of Arizona, USA, showed that the implantation rate, clinical pregnancy rate, and live birth rate were higher in women who obtained oocytes for ART in summer than in other seasons [ 11 ].…”

Seasonal variation, temperature, day length, and IVF outcomes from fresh cycles

“…When investigating solar and meteorological patterns on the day of oocyte retrieval, both longer day length and higher temperature revealed positive associations with the clinical outcomes assessed. These observations are consistent with prior studies in Israel and China reporting improved clinical IVF outcomes in the summer [14,19,21] as compared with spring and winter. Prior research has also suggested that longer day length [21,26] may be associated with positive clinical outcomes.…”

“…Available evidence for seasonal variation and IVF success is conflicting possibly due to small sample sizes (≤ 1000 cycles) and varying environmental exposures and geographic populations. Some studies on season and IVF outcomes have found no association [14][15][16][17][18], while some have suggested higher implantation and livebirth rates for IVF cycles started in the spring and summer [19][20][21]. Other studies have suggested higher positive IVF outcomes for cycles started in the fall and winter [22,23].…”

Temperature and preeclampsia: Epidemiological evidence that perturbation in maternal heat homeostasis affects pregnancy outcome

“…Additionally, our observation may be relevant to the effect of global warming. The burden of climate change on health affecting the most unprotected layers in the population has been well established by others [47][48][49]. In addition, we present here evidence that global warming may have an effect on human reproduction and maternal and/or fetal/neonatal morbidity and mortality.…”