An 11-year nationwide registry-linkage study of opioid maintenance treatment in pregnancy in Norway

Abstract

Aim: We aimed to describe opioid maintenance treatment (OMT) to pregnant women in Norway and study thebackground characteristics of the pregnant women compared to the general population of pregnant women andto a previous clinical cohort study of OMT in pregnancy.Methods: Population-based cohort study with linked data from the Norwegian Medical Birth Registry, theNorwegian Prescription Database, the Norwegian Patient Registry, and Statistics Norway. The study populationconsisted of women giving birth between 2005-2015 in Norway. We defined OMT pregnancies as pregnancieswhere the woman was dispensed OMT medications (methadone, buprenorphine, or buprenorphine/naloxone) at least once during pregnancy.Results: The study population consisted of 420,808 women with 645,440 pregnancies ending in a live birth inNorway in 2005-2015 (the general pregnant population). Of these, 261 women (0.6‰) had altogether 306OMT pregnancies. The mean number of pregnancies was 28 OMT pregnancies per year and quite stable duringthe study period. Women with OMT pregnancies were older, smoked tobacco more frequently, had lowereducation, and fewer of them had a partner, compared to the general population of pregnant women. In mostpregnancies, the women were treated with buprenorphine (n=183 (59.8%)), while in 120 (39.2%) pregnancies,the woman received methadone. From 2008, buprenorphine replaced methadone as the most frequently useddrug. In only 38 (12.4%) pregnancies, OMT treatment was initiated in pregnancy. In 201 (66%) pregnancies,the woman used OMT medications in all trimesters. For these women, the mean amount of dispensed drug was3.4 DDD/day (85 mg/day) in pregnancy for methadone and 1.9 DDD/day (15.2 mg/day) for buprenorphine.Conclusion: The number of OMT pregnancies per year has been low and stable in the period 2005-2015.Following Norwegian recommendations, there has been a shift from treatment with methadone towardsbuprenorphine. The women receiving OMT during pregnancy had more risk factors for adverse outcomes thanthe general pregnant population but were quite similar to the previous clinical cohort.

Children had increased risks of impaired motor and visual‐motor skills after prenatal exposure to opioid maintenance therapy

“…29 Collectively, it is probable that the drug dose burden on the foetal brain might influence a child's functional outcome. The mean methadone and buprenorphine doses, 85 mg and 13 mg, respectively, in our study are comparable to doses of 85 mg methadone and 15 mg buprenorphine reported in a Norwegian register study, 30 and a Swedish study, 25 reflecting a relatively high common Scandinavian dose regime.…”

Visual function in Norwegian children aged 5–13 years with prenatal exposure to opioid maintenance therapy: A case–control study

“…As opposed to other countries, Norway has a law that protects the foetus; if any illicit drug use is considered to harm foetal health; the mother will be treated in an inpatient clinic, either voluntarily or under duress. Of additional importance is that most OMT women in Norway (85%–90%) are already in OMT before they become pregnant (Odsbu et al, 2021). Taken together, this may explain the lower prevalence of polydrug use (21%) and alcohol (8%) in this study compared to previous studies.…”

Children born to women in opioid maintenance treatment: A longitudinal study of child behavioral problems and parenting stress

“…To date, OMT in Norway includes ∼8,000 individuals, onethird being women. The number of pregnancies in the OMT program has been low and stable in the period 2005-2015 with a mean number of 28 pregnancies per year, representing 0.06% of the general pregnant population in Norway during the same time period (34).…”