The use of record linkage to examine illicit drug use in pregnancy

Aims  To examine the obstetric and perinatal outcomes for women with a drug‐related hospital admission during pregnancy. Design  Antenatal and birth admissions to New South Wales (NSW) hospitals from the NSW Inpatient Statistics Collection were linked to birth information from the NSW Midwives Data Collection over a 5‐year period (1998–2002). Measurements  Birth admissions were flagged as positive for drug use where a birth admission or any pregnancy admission for that birth involved an opioid, cannabis or stimulant‐related International Classification of Diseases version 10 Australian modification (ICD‐10AM) code. Findings  A total of 416 834 live births were analysed over a 5‐year period (1998–2002). Of these, 1974 pregnancies had an opioid ICD‐10AM diagnosis recorded, 552 a stimulant‐related ICD‐10AM and 2172 a cannabis ICD‐10AM diagnosis. Births in each of the drug groups were to women who were younger, had a higher number of previous pregnancies, were indigenous, smoked heavily and were not privately insured. These women also presented later in their pregnancy to antenatal services and were more likely to arrive at hospital unbooked. Neonates born to women in each of the drug groups were more likely to be premature and were admitted to neonatal intensive care and special care nursery more often, with neonates born to women in the opioid group admitted most often. Conclusions  Linked population level administrative data is a powerful method for examining the maternal and neonatal outcomes associated with the use of specific illicit drugs during pregnancy.