Heat linked to fewer births in France and Italy

Two studies have found that intense heat is associated with a decrease in births nine to ten months later in France and Italy. Each day with an average temperature of 25 °C or higher is linked to about 360 fewer births in France and about 192 fewer in Italy. The studies consider this link real but relatively weak.

Heat may affect reproductive health

The decline in births appears nine to ten months after exposure to heat, suggesting fewer conceptions during hot months. Heat can affect the reproductive health of men and women, potentially leading to fewer pregnancies. It can also influence sexual behavior, though both explanations are possible.

Other countries also see similar trends

Similar studies in the United States, South Korea, Spain, and across Europe have also found a link between heat and a decline in births. Earlier studies in the United States and Hungary suggested that some missing births were made up in subsequent months, but the French and Italian studies show no such pattern, indicating that some births may be permanently lost.

Fertility rates are already declining

Italy and France are already experiencing declining fertility rates. Italy was one of the first countries to fall below the 1.30 children per woman threshold in the 1990s. France has maintained a higher fertility rate for longer but has seen a 24% decline in births between 2010 and 2025.

Europe is warming rapidly

Europe is warming faster than other continents, with some regions becoming regional heatwave hotspots. The Mediterranean, in particular, is highly exposed, with Italy experiencing an average temperature increase of nearly 2 °C over the last sixty years. Europe experienced several long and severe heatwaves this summer, with France's heatwave being the hottest since 1900.

Studies have limitations and broader factors

The studies have limitations, as they rely on data from past decades and may not reflect current or future conditions. The link between heat and births is real but relatively weak, with changes in family norms and financial concerns being the main factors behind declining fertility. However, if heat episodes become more frequent and intense, climate change could play a more significant role in the future.