Postpartum hormonal contraceptive use in Denmark during 1997-2021

Introduction: Hormonal contraception is used by over a quarter of a billion worldwide. In Denmark, 84% have used it before their first pregnancy. After pregnancy, mothers are routinely advised to consider contraception to avoid short interpregnancy intervals due to perinatal and maternal health risks. Yet, mothers are not recommended to start combined hormonal contraception within six weeks postpartum due to an increased thromboembolic risk. This study provides an overview of postpartum hormonal contraceptive use in Denmark. Material and methods: This descriptive study is based on Danish national health registries on mothers who delivered during 1997-2021. The cumulative incidence of HC initiation one year after delivery is reported by calendar year and age group. Timing of initiation is reported as the median time from delivery. Hormonal contraception was categorized according to hormone type and method of administration. Results: A total of 676 759 first-time and 552 142 second-time mothers were registered, with a cumulative incidence of hormonal contraceptive initiation of 41.0% (95% CI, 40.9-41.1) and 40.5% (95% CI, 40.4-40.6), respectively. From 1997 to 2021, the cumulative incidence of first-time mothers who initially used progestogen-only pills increased from 3.8% (95% CI, 3.5-4.0) to 14.4% (95% CI, 13.9-14.8) and intrauterine levonorgestrel-releasing systems from 0.1% (95% CI, 0.1-0.2) to 12.6% (95% CI, 12.3-13.0). In contrast, combined oral contraception initiation decreased from 31.3% (95% CI, 30.7-31.8) to 7.8% (95% CI, 7.5-8.2). Among first-time mothers initiating hormonal contraception, the median time of initiation decreased from 4.7 (Q1-Q3, 2.5-7.5) months during 1997-2001 to 2.5 (Q1-Q3, 2-0-4.0) months during 2017-2021. The cumulative incidence of first-time mothers using combined hormonal contraception six weeks after delivery decreased from 1.5% (95% CI, 1.5-1.6) during 2007-2011 to 0.5% (95% CI, 0.5-0.5) during 2017-2021. Conclusions: Within the first year after childbirth, 41% of first- and second-time mothers initiated hormonal contraception in Denmark during 1997-2021. Throughout 1997-2021, mothers started earlier after delivery and more often used progestogen-only contraception. Few started combined hormonal contraception within 6 weeks after delivery in accordance with national guidelines. Taken together, the pattern of HC use over time reflects a change to safer contraceptive methods postpartum which minimizes thromboembolic risk. ### Competing Interest Statement VGF has received honorarium as a speaker for Lundbeck Pharma A/S, Janssen-Cilag A/S and Gedeon-Richter A/S. Juliane Marie Center has received research funding from Exeltis. KBM has received speaker's fee from Medice Nordic within the last three years. TMO has received a speaker honorarium from Lundbeck Pharma A/S. The rest of the authors report no conflicts of interest. ### Funding Statement The study was funded by The Independent Research Fund Denmark (grant identifier: 0134-00278B and 7025-00111B). The funder had no role in the design and conduct of the study; collection, management, analysis, and interpretation of the data; preparation, review, or approval of the manuscript; and decision to submit the manuscript for publication. ### Author Declarations I confirm all relevant ethical guidelines have been followed, and any necessary IRB and/or ethics committee approvals have been obtained. Yes The details of the IRB/oversight body that provided approval or exemption for the research described are given below: This is a register study. No ethical approval or informed consent are required for register-based studies in Denmark. Danish e-Health Authority gave approval for this work. The Regional Danish Data Health Board, Privacy, gave approval for his study, journal-nr. Pactius-2020-217 I confirm that all necessary patient/participant consent has been obtained and the appropriate institutional forms have been archived, and that any patient/participant/sample identifiers included were not known to anyone (e.g., hospital staff, patients or participants themselves) outside the research group so cannot be used to identify individuals. Yes I understand that all clinical trials and any other prospective interventional studies must be registered with an ICMJE-approved registry, such as ClinicalTrials.gov. I confirm that any such study reported in the manuscript has been registered and the trial registration ID is provided (note: if posting a prospective study registered retrospectively, please provide a statement in the trial ID field explaining why the study was not registered in advance). Yes I have followed all appropriate research reporting guidelines, such as any relevant EQUATOR Network research reporting checklist(s) and other pertinent material, if applicable. Yes Danish national health register data cannot be distributed, but access to the data can be granted by the appropriate authorities