Maternal heat exposure before conception linked to miscarriage

A study by University of KwaZulu-Natal (UKZN) scientists has found a clear relationship between maternal heat exposure during the month preceding conception and miscarriage in a sub-Saharan African setting.

The scientists believe that it is likely that progressive climate change leading to increased temperatures will exacerbate existing challenges for women’s reproductive health in this region resulting in increased pregnancy loss.

The study investigated the relationship between maternal heat exposure and miscarriage (pregnancy ending before 20 weeks gestation) in a rural community in the uMkhanyakude District of KwaZulu-Natal between 2012 and 2016.

The community has been monitored for over two decades as part of the Africa Health Research Institute’s Health and Demographic Surveillance System.

Scientists included Dr Yoshan Moodley who is a Clinical Research Fellow in the School of Clinical Medicine and Nursing as well as Public Health academics, Professor Frank Tanser, Andrew Tomita and Dr Kwabena Asare.

Although most of the evidence around the impact of higher temperatures on pregnancy outcomes has been based on studies of the prenatal period, the scientists felt that maternal exposure to high temperatures during the preconception period is also an important factor in understanding issues around women’s health in this setting.

This region was selected as the two most important public health problems facing women of childbearing age in the uMkhanyakude District, includes a high HIV incidence and a high maternal mortality ratio of 650 maternal deaths per 100 000 live births.

“Maternal exposure to an increasing number of hot days during the month prior to conception was associated with an increased risk of miscarriage,” said the lead author of the study, Dr Moodley.

“These findings suggest that extreme heat exposure during the preconception period is harmful to human oocytes (a developing egg), but this would require further physiological and clinical investigation beyond the scope of our population-based analysis.”

The scientists used data from the South African Weather Service to compute maternal exposure to heat during the month preceding conception and during the week preceding the study outcome (either a miscarriage or no miscarriage). Heat exposure was measured as the mean number of days the mother was exposed to temperatures more than 26.6 degrees Celsius.

A total of 105 out of 3477 pregnancies included in the analysis ended in miscarriage (3.0%). Each additional hot day during a month prior to conception was associated with a 26% increase in the relative risk of miscarriage for the women.

Senior author of the study, Mr Tomita said climate change poses existential threat to all, but pregnant women in resource-limited rural sub-Sahara Africa bear some of the most severe consequences.

“We believe there is inadequate attention to maternal health in the discourse, and much work needs to be done to safeguard pregnant women from the impacts of climate change in rural sub-Saharan Africa,” said Mr Tomita.