title: Pre-gravid oral contraceptive use in relation to birth weight: a prospective cohort study.
abstract: Few studies have evaluated the association between pregravid oral contraceptive (OC) use and birth weight, and findings have been conflicting. We conducted a prospective cohort study of 5921 pregnancy planners in Denmark to evaluate recency, duration, and type of OC used before conception in relation to infant birth weight. Participants completed online questionnaires and reported detailed information on contraceptive history and covariates at baseline. Participants completed bimonthly follow-up questionnaires to update their pregnancy status for up to 12 months or until conception occurred. Birth weight data were ascertained from the Danish Medical Birth Registry for 4046 live births delivered by study participants between 2008 and 2010. We used multivariable linear and log-binomial regression analyses to control for confounding. Mean birth weight was higher among women who had used OCs within 0-1 months (mean difference = 97 g, CI 26, 168) or 2-6 months (mean difference = 40 g, CI -5, 85) before conception, compared with more than 12 months before conception. Mean birth weight was lower among women who had used OCs for long durations (mean difference comparing ≥12 with <4 years of OC use = -85 g, CI -158, -11). Our findings indicate that pregravid OC use within 6 months of conception may be associated with a small increase in birth weight, but that long duration of use may have the opposite effect. Results were stronger among male infants, among 2nd and 4th generation OC users, and among users of OCs with a higher estrogen dose.
authors.affiliation: Department of Epidemiology, Boston University School of Public Health, Boston, MA, USA. eehatch@bu.edu.
authors.forename: Elizabeth E
authors.identifier: http://orcid.org/0000-0001-7901-3928
authors.initials: EE
authors.lastname: Hatch
authors.affiliation: Department of Epidemiology, Boston University School of Public Health, Boston, MA, USA.
authors.forename: Kristen A
authors.initials: KA
authors.lastname: Hahn
authors.affiliation: Department of Clinical Epidemiology, Aarhus University Hospital, Aarhus, Denmark.
authors.forename: Ellen M
authors.initials: EM
authors.lastname: Mikkelsen
authors.affiliation: Department of Clinical Epidemiology, Aarhus University Hospital, Aarhus, Denmark.
authors.forename: Anders H
authors.initials: AH
authors.lastname: Riis
authors.affiliation: Department of Clinical Epidemiology, Aarhus University Hospital, Aarhus, Denmark.
authors.forename: Henrik Toft
authors.initials: HT
authors.lastname: Sorensen
authors.affiliation: Department of Epidemiology, Boston University School of Public Health, Boston, MA, USA.|RTI Health Solutions, Research Triangle Park, NC, USA.
authors.forename: Kenneth J
authors.initials: KJ
authors.lastname: Rothman
authors.affiliation: Department of Epidemiology, Boston University School of Public Health, Boston, MA, USA.|Slone Epidemiology Center, Boston University, Boston, MA, USA.
authors.forename: Lauren A
authors.initials: LA
authors.lastname: Wise
mesh_terms: D000293:Adolescent; D000328:Adult; D001724:Birth Weight / Q000187:drug effects*; D015992:Body Mass Index; D003268:Contraception Behavior / Q000208:ethnology*; D003276:Contraceptives, Oral / Q000009:adverse effects*; D003718:Denmark / Q000453:epidemiology; D005260:Female; D005320:Fetal Macrosomia / Q000453:epidemiology*; D005500:Follow-Up Studies; D006801:Humans; D007236:Infant, Small for Gestational Age; D008423:Maternal Age; D015999:Multivariate Analysis; D011247:Pregnancy; D011248:Pregnancy Complications; D011446:Prospective Studies; D017584:Reproductive History; D012307:Risk Factors; D012959:Socioeconomic Factors; D011795:Surveys and Questionnaires; D013997:Time Factors
chemical_list: D003276:Contraceptives, Oral
keywords: Birth weight; Oral contraceptives; Ponderal index; Prospective cohort study