Objective During a study of weight faltering it was observed that infants from a minority Haredi (ultra-Orthodox Jewish) religious group showed very different growth patterns from the rest of the cohort. The authors thus set out to explore the characteristics of the community that may explain these differences.

Setting and subjects Gateshead Millennium Study cohort, UK.

Design Prospective population-based cohort study of 961 term infants (of whom 33 were from the Haredi community) recruited shortly after birth and followed by postal questionnaires and measurement at age 13 months.

Results At birth Haredi children had similar weights to the rest of the cohort, but by the age of a year the Haredi babies were significantly lighter (mean difference −1.06; p<0.001) and shorter even after allowing for parental heights (length z score mean difference –0.5; p=0.02). They were much more likely to have had weight faltering at some point: Haredi 48%, remainder 11%; RR=4.36; p<0.001. The Haredi families were much larger (54% had 5–12 siblings) were breast fed for longer (67% >4 months vs 15% of remainder; p<0.01) and started solids later (mean difference (CI) 7.5 (5.3 to 9.8) weeks; p<0.001) and these factors largely explained the differences in weight gain.

Conclusions The extreme growth patterns seen in these children seem to relate to large family size and delayed and inadequate introduction of complementary solids, which are known risk factors for malnutrition in less affluent societies.