Dataset Information

Maternal use of oral contraceptives and risk of birth defects in Denmark: prospective, nationwide cohort study.

ABSTRACT:

Study question

Is oral contraceptive use around the time of pregnancy onset associated with an increased risk of major birth defects?

Methods

In a prospective observational cohort study, data on oral contraceptive use and major birth defects were collected among 880,694 live births from Danish registries between 1997 and 2011. We conservatively assumed that oral contraceptive exposure lasted up to the most recently filled prescription. The main outcome measure was the number of major birth defects throughout one year follow-up (defined according to the European Surveillance of Congenital Anomalies classification). Logistic regression estimated prevalence odds ratios of any major birth defect as well as categories of birth defect subgroups.

Study answer and limitations

Prevalence of major birth defects (per 1000 births) was consistent across each oral contraceptive exposure group (25.1, never users; 25.0, use >3 months before pregnancy onset (reference group); 24.9, use 0-3 months before pregnancy onset (that is, recent use); 24.8, use after pregnancy onset). No increase in prevalence of major birth defects was seen with oral contraceptive exposure among women with recent use before pregnancy (prevalence odds ratio 0.98 (95% confidence interval 0.93 to 1.03)) or use after pregnancy onset (0.95 (0.84 to 1.08)), compared with the reference group. There was also no increase in prevalence of any birth defect subgroup (for example, limb defects). It is unknown whether women took oral contraceptives up to the date of their most recently filled prescription. Also, the rarity of birth defects made disaggregation of the results difficult. Residual confounding was possible, and the analysis lacked information on folate, one of the proposed mechanisms.

What this study adds

Oral contraceptive exposure just before or during pregnancy does not appear to be associated with an increased risk of major birth defects.

Funding, competing interests, data sharing

BMC was funded by the Harvard T H Chan School of Public Health's Maternal Health Task Force and Department of Epidemiology Rose Traveling Fellowship; training grant T32HD060454 in reproductive, perinatal, and paediatric epidemiology and award F32HD084000 from the Eunice Kennedy Shriver National Institute of Child Health and Human Development; and grant T32CA09001 from the National Cancer Institute. The authors have no competing interests or additional data to share.

SUBMITTER: Charlton BM

PROVIDER: S-EPMC4703703 | biostudies-literature |

REPOSITORIES: biostudies-literature

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Project description:ObjectiveTo examine the association between the use of macrolide antibiotics in pregnancy and the risk of major birth defects.DesignNationwide, register based cohort study.SettingDenmark, 1997-2016.ParticipantsOf 1 192 539 live birth pregnancies, pregnancies during which macrolides had been used (13 019) were compared with those during which penicillin (that is, phenoxymethylpenicillin) had been used (matched in a 1:1 ratio on propensity scores). Other comparative groups were pregnancies when macrolides had been used recently but before pregnancy (matched 1:1) and pregnancies where no antibiotics had been used (matched 1:4).Main outcome measuresAssociation with an outcome of any major birth defect and specific subgroups of birth defects were assessed by relative risk ratios and absolute risk differences.ResultsIn matched comparisons, 457 infants were born with major birth defects to women who had used macrolides during pregnancy (35.1 per 1000 pregnancies) compared with 481 infants (37.0 per 1000 pregnancies) to women who had used penicillin (relative risk ratio 0.95; 95% confidence interval 0.84 to 1.08), corresponding to an absolute risk difference of -1.8 (95% confidence interval -6.4 to 2.7) per 1000 pregnancies. The risk of major birth defects was not significantly increased for women who had used macrolides during pregnancy compared with those who had used macrolides recently but before becoming pregnant (relative risk ratio 1.00 (95% confidence interval 0.88 to 1.14); absolute risk difference -0.1 (95% confidence interval -4.8 to 4.7) per 1000 pregnancies) or compared with women who did not use any antibiotics (1.05 (0.95 to 1.17); 1.8 (-1.7 to 5.3) per 1000 pregnancies). For all three comparative group analyses and in the analyses of use of individual macrolides, no significant increased risk of specific subgroups of birth defects associated with the use of macrolides was found.ConclusionsIn this nationwide cohort study, the use of macrolide antibiotics in pregnancy was not associated with an increased risk of major birth defects. Analyses of the associated risk of 12 specific subgroups of birth defects with the use of macrolides in pregnancy were not significant.

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