Ramadan during pregnancy and offspring health over the life course: A systematic review

BACKGROUND: The Muslim population in Europe is increasing, with by now more than 5% of the population being Muslim. During pregnancy, many Muslim women choose to adhere to the Ramadan fast. Research on health effects of Ramadan during pregnancy on the offspring has been conducted through two separate literature strands. One compares offspring of women who chose vs didn't choose to fast and focuses on birth outcomes. The other strand uses an ITT-approach, classifying Muslims as potentially vs certainly not exposed based on their birthdates relative to Ramadan. The ITT-studies’ design allows to also study later-life health. This review combines both strands and evaluates their ability to identify causal effects between Ramadan during pregnancy and offspring health. METHODS: A systematic literature search using PubMed, EconLit and Web of Science plus a Google Scholar search yielded 35 eligible studies. Data were extracted and quality assessed using a checklist. RESULTS: Non-ITT studies often struggle to adequately address bias from self-selection in treatment, with a high risk of confounding and unknown direction of bias. ITT studies, while producing results biased toward zero, are likely to reveal causality and relied on large datasets, leading to high statistical power. Studies meeting the quality threshold find limited evidence of effects on birth outcomes, such as birthweight, but show increased child mortality rates and worse adult health outcomes along several dimensions. These effects tend to increase in magnitude with age, which is congruent with fetal programming theory. CONCLUSIONS: Medical advisories, guidelines and previous literature reviews mostly focused on non-ITT studies that primarily examined birth outcomes. However, health effects mostly show up at later ages. Consequently, adverse long-run effects are often overlooked, and pregnant Muslims remain not fully informed of potential health impacts on their offspring of their Ramadan fasting decisions. KEY MESSAGES: • Many pregnant Muslims decide to fast during Ramadan. Rigorous quality checking of the research on offspring health effects is needed to provide informative evidence for the growing Muslim population. • Adverse health effects of Ramadan during pregnancy mostly become visible only years after birth. Medical advisories tend to focus on evidence on birth effects, overlooking long-term adverse effects.