News | Study finds higher summer miscarriage risk, especially before 8 weeks
Although up to 30% of pregnancies end in miscarriage, many losses remain unexplained. A Boston University School of Public Health (BUSPH) study found seasonal variation for the first time: early miscarriage risk rose significantly in summer, especially in late August.
Led by BUSPH research assistant professor of epidemiology Amelia Wesselink, PhD, the study was published in Epidemiology in 2022.
Does miscarriage risk vary by season? Highest in late August
In North America, miscarriage within the first 8 weeks was 44% more likely in summer than in February. Across all gestational ages, overall risk was 31% higher in late August than late February.
Geography also mattered. Risk was higher in late August and early September in the southern and midwestern United States, the hottest regions each summer.
“Seasonal variation in a health outcome prompts us to investigate why,” Dr. Wesselink said. “Miscarriage risk peaked in summer, particularly for losses in the first 8 weeks. We now need to study which summer exposures may explain this.”
Data from the large, long-term U.S. PRESTO study
The study used PRESTO (Pregnancy Study Online), a prospective web-based pregnancy study funded by the National Institutes of Health (NIH) since 2013.
PRESTO enrolls women trying to conceive and follows them from preconception through six months postpartum. This analysis included 6,104 women who conceived within one year and reported the timing and gestational age of pregnancy loss.
Earlier miscarriage studies often relied on clinical or fertility-clinic data, missing many early losses outside the health system. PRESTO better reflects the general population.
Is heat responsible? Climate change may affect pregnancy outcomes
The study did not prove that heat causes miscarriage, but researchers proposed heat exposure as a possible explanation.
“Very few studies have examined heat and miscarriage,” Dr. Wesselink said. “More work is needed, but evidence already warrants close attention from clinicians, policymakers, and climate experts.”
Heat exposure is already associated with preterm birth, low birth weight, and stillbirth.
Dr. Wesselink called for heat to be included in medical guidance and public-health policy, including heat action plans and climate-adaptation strategies that assess risks to pregnant women and fetuses.
Research team
BUSPH epidemiologists on the study included:
Kenneth Rothman, PhD (BUSPH professor of epidemiology and senior author)
Lauren Wise, PhD
Elizabeth Hatch, PhD
Ellen Mikkelsen, PhD, Aarhus University, Denmark
David Savitz, PhD, Brown University School of Public Health
Kipruto Kirwa, PhD, Tufts University School of Medicine
News | Study finds higher summer miscarriage risk, especially before 8 weeks
News | Study finds higher summer miscarriage risk, especially before 8 weeks
Although up to 30% of pregnancies end in miscarriage, many losses remain unexplained. A Boston University School of Public Health (BUSPH) study found seasonal variation for the first time: early miscarriage risk rose significantly in summer, especially in late August.
Led by BUSPH research assistant professor of epidemiology Amelia Wesselink, PhD, the study was published in Epidemiology in 2022.
Does miscarriage risk vary by season? Highest in late August
In North America, miscarriage within the first 8 weeks was 44% more likely in summer than in February. Across all gestational ages, overall risk was 31% higher in late August than late February.
Geography also mattered. Risk was higher in late August and early September in the southern and midwestern United States, the hottest regions each summer.
“Seasonal variation in a health outcome prompts us to investigate why,” Dr. Wesselink said. “Miscarriage risk peaked in summer, particularly for losses in the first 8 weeks. We now need to study which summer exposures may explain this.”
Data from the large, long-term U.S. PRESTO study
The study used PRESTO (Pregnancy Study Online), a prospective web-based pregnancy study funded by the National Institutes of Health (NIH) since 2013.
PRESTO enrolls women trying to conceive and follows them from preconception through six months postpartum. This analysis included 6,104 women who conceived within one year and reported the timing and gestational age of pregnancy loss.
Earlier miscarriage studies often relied on clinical or fertility-clinic data, missing many early losses outside the health system. PRESTO better reflects the general population.
Is heat responsible? Climate change may affect pregnancy outcomes
The study did not prove that heat causes miscarriage, but researchers proposed heat exposure as a possible explanation.
“Very few studies have examined heat and miscarriage,” Dr. Wesselink said. “More work is needed, but evidence already warrants close attention from clinicians, policymakers, and climate experts.”
Heat exposure is already associated with preterm birth, low birth weight, and stillbirth.
Dr. Wesselink called for heat to be included in medical guidance and public-health policy, including heat action plans and climate-adaptation strategies that assess risks to pregnant women and fetuses.
Research team
BUSPH epidemiologists on the study included:
Kenneth Rothman, PhD (BUSPH professor of epidemiology and senior author)
Lauren Wise, PhD
Elizabeth Hatch, PhD
Ellen Mikkelsen, PhD, Aarhus University, Denmark
David Savitz, PhD, Brown University School of Public Health
Kipruto Kirwa, PhD, Tufts University School of Medicine
Source:
Collected online