Delivery of singleton preterm infants in New South Wales, 1990-1997.

OBJECTIVE: To examine trends in the maternal characteristics and delivery of singleton preterm infants in an Australian population.

DESIGN: Population-based descriptive study.

SETTING: New South Wales (NSW), Australia.

POPULATION: The population included 37 500 singleton preterm births from 1 January 1990 to 31 December 1997.

METHODS: Data were obtained from the NSW Midwives' Data Collection (MDC) and rates over time were calculated. Preterm birth by Caesarean section before the onset of labour or where labour was induced were considered to be medically indicated.

MAIN OUTCOME MEASURES: Preterm rates, medically indicated preterm birth rates, mode of delivery andneonatal outcomes, and trends over time.

RESULTS: Among singleton infants, there was no significant change over time in the rate of preterm birth (annual average 5.5%), preterm births that were medically indicated (annual average 29.3%) or neonatal outcomes of preterm births. The rate of indicated preterm birth varied by gestational age and was highest (39.7%) at 29-32 weeks' gestation. Instrumental preterm births declined over time from 9.5 to 7.8% with a shift from forceps to vacuum use and episiotomy rates declined from 19.7 to 14.8%.

CONCLUSIONS: Increases in the reported overall preterm rate (singletons and multiples) were not due to increased delivery of singleton infants. Changes in the management of singleton preterm births were similar to changes observed in term births such as decreasing forceps and episiotomy usage. It may be to time to reassess whether Australian clinicians would be willing to randomise patients to clinical trials of the best method of delivery for preterm infants.