Mexico analysis links heat waves to up to 18% more preterm births

An analysis of more than 8 million birth records in Mexico showed that exposure to prolonged heat waves in the final month of pregnancy is associated with an increase in the rate of preterm births of up to 18%. Nation Kenya reports on the findings of the Reuters investigation.

Heat is becoming more widespread

Reuters calls the largest heat waves “heat storms.” For its analysis, the agency defined a heat wave as at least five consecutive days when temperatures fall within the highest 10% of the historical range for a particular location. The largest such events, which at their peak cover at least 1% of the planet, were classified as heat storms.

According to an analysis of hourly temperature data since 1960, 50 heat storms were recorded in the 1960s, while there have already been more than 665 in the current decade. The largest of them covered nearly 85% of the planet over the course of a year.

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Risks for pregnant women

Scientific studies link temperature spikes to a higher likelihood of dangerous hypertension, infections, congenital defects, miscarriages and stillbirths. The clearest association is with preterm births, which can have serious long-term health consequences.

Researchers draw attention not only to absolute temperature but also to heat that is unusual for a person: every 1-degree-Celsius increase above the usual level is associated with harm to pregnancy. Similar complications have been documented in studies in China, Australia, South Africa and the United States.

The mechanism of impact is still being studied

Scientists do not yet have an unambiguous explanation of exactly how high temperatures harm pregnancy. Possible mechanisms include the redistribution of blood away from the placenta to cool the mother’s body and additional strain on the fetal heart. Doctors in Johannesburg and Miami are already using various protective measures, from wide-brimmed hats and white-painted roofs to air conditioners.