Abstract 583 Poster Session I, Saturday, 5/1 (poster 184)

An increase in preterm deliveries in Ribeirao Preto stimulated an analysis of factors associated with it. Two cohorts of singleton livebirths were studied, the first based on 6746 births in 1978/1979 and the second based on 2846 births in 1994. Preterm birth rate rose from 7.6% in 1978/1979 to 13.6% in 1994. A logistic regression was carried out to assess the association of preterm birth with several socio-demographic, behavioural and clinical variables including year of survey. Delivery in private settings (OR 1.34, 95% CI 1.02-1.75) in comparison to a public setting, maternal age of 17 or less (OR 1.00) in comparison to any other age group (18 and 19 years: OR 0.50, 95% CI 0.34-0.71; 20 to 24: OR 0.47, 95% CI 0.35-0.64; 25 to 29: OR 0.45, 95% CI 0.33-0.61; 30 to 34: OR 0.46, 95% CI 0.32-0.65; 35 years and over: 0.58, 95% CI 0.40-0.84)), mothers who had previous abortions (OR 1.42, 95% CI 1.16-1.74) and previous stillbirths (OR 1.78, 95% CI 1.16-2.71) were associated with greater rates of preterm birth. There was a significant interaction between year of survey and mode of delivery on preterm birth rate, showing over time a greater increase of preterm births in caesarean section deliveries than in vaginal deliveries (table).

Table 1 The association between type of delivery and year of survey on preterm birth rates among singleton livebirths in Ribeirao Preto.
Full size table

Over the study period deliveries in private hospitals increased from 4% to 36% and caesarean section operations increased from 30.3% to 50.8%. Deliveries in private facilities are a possible factor responsible for the increase in preterm rate and caesarean section may have contributed to it. It is essential to learn how monitoring technology in obstetrics is being used and ensure that health staff using private facilities are properly audited and educated.