Vinding, Stokholm, Chaves, Bønnelykke and others, in the present issue of the American Journal of Clinical Nutrition, report potentially harmful offspring effects of taking supplements with long chain n-3 fatty acids, also known as n-3 polyunsaturated fatty acids (LCPUFAs) in pregnancy [1]. They examined the impact of maternal supplementation with fish oil during gestation, starting in week 24, on offspring growth and metabolic health assessed when the children were 10 y old. The study was based on follow-up from an influential trial in the field, the COPSAC2010 Study, which in 2016 provided evidence that fish oil could reduce offspring risk of persistent wheeze or asthma and infections of the lower respiratory tract, assessed up to age 5 y [2]. A number of additional studies focusing on a range of different outcomes in children have since been published based on this very same trial population. In the present work, the authors undertook physical examinations of the children at 10 y of age [1]. This publication succeeds 2 earlier publications from the trial cohort, where related outcomes were studied, one reporting increased birth weight for gestational age after maternal supplementation with n-3 LCPUFA, and the other reporting increased BMI during ages 1 to 6 y (several assessments were undertaken of BMI during this age span), as well as increased lean mass, bone mass, and fat mass (assessed by dual x-ray absorptiometry scan) at 6 y. Based on this new analysis, the authors infer that children of mothers receiving long chain n-3 fatty acids in pregnancy seem to have increased BMI, increased risk of being overweight, a tendency of increased fat percentage, and higher metabolic syndrome score at the age of 10