BACKGROUND: Heroin availability and purity decreased precipitously in Australian markets between 2000 and 2001. This led to increased use of non-opiate drugs in the general community but whether pregnant drug users and their newborn infants were affected remains unknown. AIM: To determine if perinatal drug exposure and outcomes are affected by changes in street drug availability. METHODS: Retrospective review was carried out of known drug-exposed mothers delivering live-born infants at the Royal Hospital for Women, Randwick, Australia (n = 316). Study periods were divided into preshortage (A = 1998-2000, n = 79), shortage (B = 2001-2002, n = 92) and post-shortage (C = 2003-2006, n = 122) periods. Cannabis-only users were excluded (n = 23). RESULTS: The percentage of confined women who admitted to using heroin decreased significantly (65%(A) vs 34%(B), P < 0.01) as did women on methadone programmes (90%(A), 80%(B), 75%(C), P = 0.024). The use of cocaine (7% (A) vs 33% (B), P = 0.031) and amphetamines (4% (A) vs 22% (C), P = 0.01), tripled. Most infants were born full-term and healthy but the duration of infant hospitalisation increased significantly from (median [interquartile range]) 8 [10, 38](A) to 13 [7, 23](C) days (P < 0.01). Approximately 50% of infants required withdrawal treatment but more needed phenobarbitone as an adjunct to morphine during the shortage (4/80 (0.5%) vs 15/93 (16%), P = 0.026), probably because of increased exposure to non-opiate drugs. CONCLUSIONS: The types of drugs used by pregnant drug users follow street trends and may affect infant hospitalisation and withdrawal treatment. Of concern is the rise in amphetamine-use and there needs to be increased vigilance for similar trends, especially in previously unidentified drug users.