Energy restriction during pregnancy is known to increase risk of preterm birth.

A recent study published in The Journal of Nutrition provides new information demonstrating that fasting during the second trimester of pregnancy may be particularly harmful. The study team, led by Nathalie Auger (University of Montreal Hospital Research Centre) and colleagues, evaluated the association between Ramadan fasting during pregnancy and risk of preterm birth for Arab women.

Preterm births were categorized on the basis of severity: extreme (22-27 wk), very (28-31 wk) and late (32-36 wk) preterm. Analyzing the birth certificates from over 3,000,000 deliveries in Quebec, Canada, the researchers identified the beginning and the end dates of Ramadan to determine if it occurred during any trimester of pregnancy.

In this study of Arabic-speaking women, Ramadan fasting during the second trimester of pregnancy was associated with a 35% greater risk of very preterm birth compared with no fasting. The risk was even greater for Ramadan fasting during weeks 22 and 27, the latter half of the second trimester. Although researchers could not confirm that all Arabic-speaking women fasted in this study, the findings provide compelling evidence that fasting during Ramadan in the second trimester of pregnancy was linked with very preterm birth, but not extreme or late preterm birth.

Moreover, fasting during Ramadan in the first trimester had no impact. This is not surprising given that, during the second trimester of pregnancy, energy requirements increase by 340 kcal/d whereas energy needs in the first trimester are no different from nonpregnant women.

Although fasting at any point during pregnancy is not advised, fasting in the critical period between 22 and 27 wk of pregnancy may be particularly risky. Pregnant women should be advised against fasting in the second trimester to reduce the risk of preterm birth.

Reference Tith RM, Bilodeau-Bertrand M, Lee GE, Healy-Profitos J, Auger N. Fasting during Ramadan Increases Risk of Very Preterm Birth among Arabic-Speaking Women. The Journal of Nutrition, Volume 149, Issue 10, October 2019, Pages 1826–1832,

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