Researchers in South Africa have alerted that global warming could increase rates of serious pregnancy problems. The findings of a new review published online in the BMJ (British Medical Journal), established that associations between temperature and pregnancy outcomes were largest among lowerincome women.
According to the study authors, this suggested that pregnant women in low- and middle- income countries may be at particular risk from heat exposure occasioned by global warming. Based on this development, study coauthor, Matthew Chersich and colleagues said: “Given increases in the frequency and intensity of heat waves, the number of pregnant women exposed to these conditions worldwide, and the significant individual and societal burdens associated with preterm birth and stillbirth, research and policy initiatives to deal with these connections are a high priority.”
Chersich is a research professor at the University of the Witwatersrand in Johannesburg, South Africa. The study team analysed 70 studies from 27 countries that reported associations between high temperatures and preterm birth, birth weight, and stillbirths, the ‘Newsmax’ reported.
According to the World Health Organisation (WHO), each year, 15 million babies worldwide are born preterm, a leading cause of death among children younger than five years.
Of the 47 studies that assessed preterm births, the average rate was 5.6 per cent, much lower than the global average of about 10 per cent. Forty of the studies found that preterm births were more common at higher than lower temperatures.
The risk of preterm birth rose, on average, by five per cent per 1° Celsius (1.8° Fahrenheit) increase in temperature and by 16 per cent during heat waves versus on non-heat wave days.
Similarly, nearly two million stillbirths occur worldwide each year. Among the eight studies that examined stillbirth, the average rate was 6.2 per 1,000 births, with about half of the rates in many lower-income countries.
All eight studies found an increase in stillbirths at higher temperatures, with stillbirths increasing by five per cent per 1° Celsius rise in temperature. In most cases, associations between temperature and stillbirth were most pronounced in the last week or month of pregnancy.
Furthermore, low birth weight is associated with a range of short- and long-term consequences. Of the 28 studies that assessed birth weight, the average rate of low birth weight was three per cent.
Eighteen of the studies found an increased risk of low birth weight at higher temperatures, but most reported only minor effects.