Role of prenatal care in preterm birth and low birthweight in portugal

Abstract

Background: It remains unclear if benefits of prenatal care can be attributed to the amount and content of care or to uncontrolled risk factors that might also affect its use. This study was designed to evaluate the independent association between prenatal care adequacy and adverse pregnancy outcomes, measured either as the occurrence of preterm birth or low birthweight. Method: We studied 3734 single liveborn infants. Information on mothers' use of prenatal care, and demographic, anthropometric, behavioural, clinical and obstetric characteristics were obtained through questionnaire. Prenatal care was classified as inadequate, intermediate or adequate based on Kessner's Adequacy of Prenatal Care Index. To estimate the association of adequacy of prenatal care and the defined outcomes, both crude and adjusted odds ratios (OR) and 95 per cent confidence intervals (95 percent CI) were calculated by means of unconditional logistic regression. Results: Adequate and intermediate (compared with inadequate) prenatal care was significantly associated with a lower risk of preterm (OR = 0⋅20, 95 per cent Cl 0⋅12–0⋅32, and OR = 0⋅35, 95 per cent Cl 0⋅23–0⋅54, respectively) or low birthweight (OR = 0⋅23, 95 per cent Cl 0⋅15–0⋅35, and OR = 0⋅31, 95 per cent Cl 0⋅20–0⋅46, respectively). After adjusting for maternal age, social class, marital status, complications of pregnancy and type of hospital, the risk of preterm delivery remained significantly lower for women receiving adequate (OR = 0⋅18, 95 per cent Cl 0⋅11–0⋅28) or intermediate care (OR = 0⋅35, 95 per cent Cl 0⋅23–0⋅54). Adjusted for maternal body mass index, marital status, cigarette smoking, pregnancy weight gain and complications, type of hospital, newborn sex and gestational age, a significant decreased risk of low birthweight remained for infants of women with adequate (OR = 0⋅39, 95 per cent Cl 0⋅23–0⋅65) or intermediate care (OR = 0⋅47, 95 per cent Cl 0⋅29–0⋅76). Conclusions: Our findings show that in a population with free access to prenatal care, the quantitative adequacy of prenatal care has an independent effect on pregnancy outcome, whether assessed through the occurrence of preterm births or low birthweight infants. © 1996, Oxford University Press.