Maternal body mass index in early pregnancy and offspring mortality up to early adulthood: A nationwide cohort study

A recent study conducted across Sweden analyzed the relationship between maternal body mass index (BMI) during early pregnancy and the mortality of offspring up to early adulthood. Obesity among women of childbearing age has become more prevalent globally, but its long-term effects on offspring's health in relation to mortality have been unclear.

To investigate this association, researchers examined 2,606,684 live births in Sweden from 1982 to 2014 (excluding 1990 and 1991) and monitored the participants until death, emigration from Sweden, or December 31, 2023, whichever occurred first. Maternal BMI was categorized into underweight (BMI <18.5), normal weight (18.5–24.9 kg/m 2 ), overweight (25–29.9 kg/m 2 ), obesity grades I–III (30–40 kg/m 2 ), and used to categorize offspring mortality risks.

All-cause mortality in offspring was significantly associated with maternal BMI, with a hazard ratio (HR) of 1.03 (95% confidence interval [CI] 1.02–1.03) for every unit increase in BMI. The analysis, adjusted for maternal characteristics such as age, education, income, marital status, country of birth, early pregnancy smoking status, and pre-existing psychiatric or cardiovascular conditions, confirmed the increased risk of premature mortality for offspring born to mothers with overweight or obesity during early pregnancy.

The study utilized cousin comparison analysis to account for potential familial confounding factors. With a median follow-up period of 22.4 years (interquartile range 14.9–30.7 years), the research found that an estimated 0.8% of offspring died during this timeframe. Given the rising rates of obesity among women of childbearing age, these findings emphasize the importance of addressing maternal BMI prior to conception to potentially improve child health outcomes. Further research is necessary to understand the underlying mechanisms behind this association.