{"doi":"10.1093/ije/dyad060","title":"The estimated effect of season and vitamin D in the first trimester on pubertal timing in girls and boys: a cohort study and an instrumental variable analysis","abstract":"BACKGROUND: Season of birth has been associated with age at menarche. Maternal vitamin D levels in pregnancy may explain this effect. We investigated whether the season of first trimester or maternal 25-hydroxyvitamin D3 [25(OH)D3] levels were associated with pubertal timing in children. METHODS: We conducted a follow-up study of 15 819 children born in 2000-03 from the Puberty Cohort, nested in the Danish National Birth Cohort (DNBC). Mean differences in attaining numerous pubertal markers, including a combined estimate for the average age at attaining all pubertal markers, were estimated for low (November-April) relative to high (May-October) sunshine exposure season in the first trimester using multivariable interval-censored regression models. Moreover, we conducted a two-sample instrumental variable analysis using season as an instrument for maternal first-trimester 25(OH)D3 plasma levels obtained from a non-overlapping subset (n = 827) in the DNBC. RESULTS: For the combined estimate, girls and boys of mothers who had their first trimester during November-April had earlier pubertal timing than girls and boys of mothers whose first trimester occurred during May-October: -1.0 months (95% CI: -1.7 to -0.3) and -0.7 months (95% CI: -1.4 to -0.1), respectively. In the instrumental variable analysis, girls and boys also had earlier pubertal timing: respectively, -1.3 months (95% CI: -2.1 to -0.4) and -1.0 months (95% CI: -1.8 to -0.2) per SD (22 nmol/L) decrease in 25(OH)D3. CONCLUSIONS: Both first pregnancy trimester during November-April and lower 25(OH)D3 were associated with earlier pubertal timing in girls and boys.","journal":"International Journal of Epidemiology","year":2023,"id":369548,"datarank":0.0,"base_score":0.0,"endowment":0.0,"self_citation_contribution":0.0,"citation_network_contribution":0.0,"self_endowment_contribution":0.0,"citer_contribution":0.0,"corpus_percentile":null,"corpus_rank":null,"citation_count":8,"citer_count":0,"citers_with_citation_signal":0,"citers_with_endowment":0,"datacite_reuse_total":0,"is_dataset":false,"is_dataset_confidence":0.9394,"is_data_producer":false,"deposit_databanks":null,"is_oa":true,"file_count":0,"downloads":0,"has_version_chain":false,"published_date":"2023-01-01","fair_score":null,"fair_percentile":null,"algorithm_id":"datarank_citation_only_1hop_v6","ranking_scope":"data_only","authors":[{"id":1128487,"name":"Nis Brix","orcid":"0000-0002-1499-8401","position":1,"is_corresponding":false},{"id":421893,"name":"Andreas Ernst","orcid":"0000-0001-5533-8891","position":2,"is_corresponding":false},{"id":1128488,"name":"Lea Lykke Harrits Lunddorf","orcid":"0000-0002-1062-770X","position":3,"is_corresponding":false},{"id":941192,"name":"Christian Lindh","orcid":"0000-0001-7435-9890","position":4,"is_corresponding":false},{"id":327125,"name":"Gunnar Toft","orcid":"0000-0002-7542-6853","position":5,"is_corresponding":false},{"id":1128489,"name":"Tine Brink Henriksen","orcid":"0000-0001-6933-8294","position":6,"is_corresponding":false},{"id":291004,"name":"Onyebuchi A. Arah","orcid":"0000-0002-9067-1697","position":7,"is_corresponding":false},{"id":327124,"name":"Cecilia Høst Ramlau‐Hansen","orcid":"0000-0003-3296-0121","position":8,"is_corresponding":false},{"id":1128486,"name":"Anne Gaml‐Sørensen","orcid":"0000-0002-5242-939X","position":0,"is_corresponding":true}],"reference_count":57,"raw_metadata":null,"created_at":"2026-07-19T01:15:32.670954Z","pmid":"37178177","pmcid":null,"fwci":null,"citation_percentile":null,"influential_citations":0,"oa_status":null,"license":null,"views":0,"total_file_size_bytes":0,"version_count":0,"fair_f":null,"fair_a":null,"fair_i":null,"fair_r":null,"fair_zscore":null,"fair_rationale":null,"fair_model":null,"fair_agent_version":null,"fair_fulltext_source":null,"fair_has_llm":null,"fair_computed_at":null,"clinical_trials":[],"software_tools":[],"db_accessions":[],"linked_datasets":[],"topics":[]}