Dataset used for the original article "Leptin and IGF-1 in infancy are associated with variants in DHCR7 and CYP2R1 that relate with type 1 diabetes and 25OHD". Uncompressed Microsoft 2013 (.xlsx) file (587 rows including headers and 56 columns) containing data collected as part of the Cambridge Baby Growth Study between 2001 and 2009. Study participants were recruited from pregnancy clinics at the Rosie Maternity Hospital, Cambridge at the first routine antenatal clinic appointment at around 12 weeks of gestation. Anthropometric assessements of the infant's size and adiposity (weight, length, skinfold thickness) were collected by trained research paediatric nurses at a minimum of one study visit scheduled within 8 days of birth and at ages 3, 12, 18, and 24 months. Samples of umbilical cord blood collected at delivery or infancy capillary blood collected at a study visit were used for DNA extraction and/or assaying hormones (C-peptide, IGF-1, IGFBP-3, and leptin). Newborn index (sex, gestational age, birth weight, singleton or twin), maternal anthropometry (pre-pregnancy weight and height), maternal presence of type 1 diabetes, parity, maternal smoking in pregnancy, parental ages, and mode of infant feeding at age 3 months were self-reported and collected as part of pregnancy and post-pregnancy questionnaires. Single nucleotide polymorphisms in vitamin D metabolism genes (rs10741657 and rs12794714 in CYP2R1, rs12785878 in DHCR7, and rs10877012 in CYP27B1) were genotyped in 612 infants who had DNA available using Kompetitive Allele Specific PCR genotyping assay by LGC Genomics.