Objectively measured perinatal exposure to meperidine and benzodiazepines in Finland

We measured concentrations of meperidine and benzodiazepines in the umbilical serum of all live neonates born in Finland during a single week. Of the neonates, 31.1% were exposed to meperidine or benzodiazepines or both. One hundred twenty-one mothers of the 261 neonates exposed to meperidine were not recorded in the Finnish Medical Birth Registry as having received analgesic drugs. Infants born to primiparous mothers were more likely to be exposed. The exposures were associated with the type of delivery: vacuum extraction with a high proportion of neonates exposed to meperidine and elective caesarean section with a high proportion of neonates exposed to benzodiazepines. The exposures were influenced by the method of obstetric analgesia: epidural blockade was associated with more frequent exposure to meperidine. No significant circadian variation in exposures was detected. Validation of birth registry data is imperative before they are used for pharmacoepidemiologic studies.