Use of prescribed opioid analgesics and co-medication with benzodiazepines in women before, during, and after pregnancy: a population-based cohort study

The aim of the study was to describe the use of prescribed opioid analgesics for noncancer pain and the degree of possible concurrent co-medication with benzodiazepines to women in Norway before, during, and after pregnancy. This was a population-based cohort study based on linkage of two nationwide registries: the Medical Birth Registry of Norway, and the Norwegian Prescription Database. Prescribed opioid analgesics and benzodiazepines issued to women 3 months prior to, during, and 3 months after pregnancies were identified. The study population consisted of 194,937 singleton pregnancies beginning in March 2004 or later and ending before January 2009. About 6% of the women were dispensed opioid analgesics before, during, or after pregnancy. Almost all these women received weak opioids (99%) with short-acting codeine in combination with paracetamol (acetaminophen) as the most frequently dispensed drug. The dispensing of codeine was reduced from 24/1,000 women before pregnancy to 10/1,000 in the last trimester, increasing to 17/1,000 during the breastfeeding period. Most women were dispensed codeine once, and treatment was of short duration (about 1 week). A small group of women (n = 271) were dispensed opioids in all trimesters. Increasing benzodiazepine use was observed as the number of opioid prescriptions increased. The use of opioid analgesics in pregnant women in Norway was dominated by treatment of short duration of the weak opioid codeine. As pregnancy proceeded, opioid use was reduced. However, the increase in opioid use during the nursing period has the potential for serious adverse effects.