“We found that miscarriage risk, particularly risk of ‘early’ miscarriage before eight weeks of gestation, was highest in the summer. Any time you see the seasonal variation in an outcome, it can give you hints about the causes of that outcome,” said Dr. Amelia Wesselink, the study lead and corresponding author.
“We know that heat is associated with a higher risk of other pregnancy outcomes, such as preterm delivery, low birth weight, and stillbirth, in particular,” Wesselink added.
Connection between Heat and Pregnancy
Dr. Gandhali Deorukhkar, consultant gynecologist, Wockhardt Hospital, India, explains that how heat is related to the risk of miscarriage. She said, “Extra heat during the summer months may lead to an increase in the core body temperature that can sometimes lead to miscarriages, but not always.”
In a study, Wesslink and colleagues analyzed data from the Boston University School of Public Health (BUSPH)-based Pregnancy Study Online (PRESTO) Survey of Pregnancy Loss, an NIH-funded project that has been ongoing since 2013, enrolling women trying to conceive and following them for up to 6 months.
After delivery, all PRESTO participants provide baseline information on sociodemographic, lifestyle and medical histories, and for this study, researchers focused on 6,104 participants who conceived within 12 months of enrollment. They provided information on the type of pregnancy loss, date of loss and weeks of pregnancy at the time of loss.
The findings begin to fill a gap in information about seasonal patterns of miscarriage. Previous studies relied on clinical or fertility data, both of which overlooked miscarriages occurring early in pregnancy (and thus, out-of-hospital) and among couples not experiencing fertility challenges.
One hypothesis is that the summertime rise in miscarriage risk is driven by exposure to heat. “Few studies have examined the association between heat and miscarriage risk, so this is definitely a topic that warrants further exploration,” says Wesslink. However, the researchers argue that doctors, policymakers and climate experts already take actions to reduce the risks associated with heat exposure during pregnancy.
“We know that heat is associated with a higher risk of other pregnancy outcomes, such as preterm delivery, low birth weight, and stillbirth, in particular,” Wesselink says. “Medical guidance and public health messaging including heat action plans and climate adaptation policies need to consider the potential effects of heat on the health of pregnant people and their babies.”
Results of the Study
The study found that pregnant women in North America had a 44% higher risk of miscarriage during the summer months especially late August than they did six months earlier in February. The risk of miscarriage at any given week of pregnancy was 31% higher in late August compared to late February.
The results further showed that, geographically, pregnant women in the South and Midwest, where summers are hotter, were more likely to experience this loss in late August and early September, respectively.
Dr. Gandhali said in response to the major reasons that could result in a miscarriage, “The problems with the genes or chromosomes can lead to a miscarriage. Most miscarriages occur because the fetus does not develop as expected. About 50% of miscarriages are associated with extra or missing chromosomes.”
“Chromosome problems might lead to the blighted ovum, a condition when no embryo forms. Other reasons could be intrauterine fetal demise or molar pregnancy and partial molar pregnancy,” she added.
Also, maternal health conditions including uncontrolled diabetes, uterine or cervical problems, infections, thyroid disease, hormonal problems, smoking and excessive alcohol consumption can lead to miscarriages.
Prevention of Miscarriage in Pregnant Women
According to Dr. Ghandali, most of the time, there’s nothing you can do to prevent a miscarriage, but the idea should always be to focus on taking good care of yourself and your baby. She had mentioned the following points to avoid miscarriage:
- Seeking regular prenatal care
- Avoiding known miscarriage risk factors such as smoking, drinking alcohol and illicit drug use
- Limiting coffee or caffeine intake a recent study found that drinking more than two caffeinated beverages a day appeared to be associated with a higher risk of miscarriage (loss of pregnancy)
- If you have a chronic condition, like hypertension or thyroid, working with your doctor to keep it under control may be beneficial
- Taking multivitamins daily