Hormonal contraceptive use in first and second interpregnancy intervals of Norwegian-born women

Abstract

Background and objective: Short interpregnancy intervals (IPIs) are associated with low birthweight and preterm births, while long IPIs may increase the risk of pre-eclampsia and small for gestational age (SGA). IPIs among Norwegian women are not described in the literature. The aim of this study is to investigate interpregnancy intervals and use of hormonal contraception between first and second births, as well as second and third births of women in Norway.

Methods: This cohort study used data from the Norwegian Prescription Database (NorPD), the Medical Birth Registry of Norway (MBRN) and Statistics Norway. The study population comprised 216 512 out of 903 704 deliveries in the MBRN between 2004-2018, and consisted of the first, second and third deliveries of Norwegian-born women with a spontaneous conception. Exposure group A represented the IPI of women with only two deliveries, while the first IPI of women with three deliveries was represented by group B1 and the second IPI by group B2. Statistical analysis was performed in SPSS version 27 with Chi-square test and T-test at significance level p<0.005.

Results: The average IPI length for study group A, B1 and B2 was 29.7, 23.7 and 32.6 months, respectively. Hormonal contraceptive use varied from 42.0% for group A, 30.2% for group B1, to 38.3% for group B2. Overall, 23.5% used POP, 8.5% used COC, and 3.9% used LNG-IUD between pregnancies. Use of vaginal ring, the patch and implant was low (0.5-1.2 %). The mean time from delivery to first contraceptive method for each exposure group was 7.9, 8.4 and 10.8 months. For older age groups, contraceptive use declines and IPIs are shorter. Proportions of no contraceptive use was high among all women with shorter IPIs.

Conclusion: Norwegian-born women had interpregnancy intervals just below two years to two years and eight months. Less than half of women used a hormonal contraceptive method between pregnancies. POP use was the most used method postpartum. The first hormonal contraceptive method is on average initiated 8-11 months postpartum. Older mothers had a lower hormonal contraceptive use and shorter IPIs compared to younger parturients.