Printed in Great Britain. Role of prenatal care in preterm birth and low birthweight in Portugal. Henrique Barros, Margarida Tavares and Teresa Rodrigues.
Vol. 18, No. 3, pp. 321-328 Printed in Great Britain
Journal of Public Health Medicine
Role of prenatal care in preterm birth and low birthweight in Portugal Henrique Barros, Margarida Tavares and Teresa Rodrigues
Introduction
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 hveborn 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 per cent Cl) 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 0-230-65) 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.
Preterm birth and low birthweight have well-known effects on infant morbidity and mortality, and several studies have shown higher rates of those outcomes for pregnant women who receive little or no prenatal care. 1 - 4 Much of the recent decline in the mortality of very low birthweight and preterm infants is attributed to high-quality perinatal care interventions rather than to the effect of programmes promoting prenatal care use. 5 However, cost-effectiveness analyses seem to favour primary prevention as the desirable option to attain the goal of reducing infant mortality, 6 and prenatal care may play a predominant role by providing a beneficial impact on pregnancy evolution and in preparing the women for the postnatal period. 7 ' 8 Significant differences in obstetric practices between countries, such as France and England, were not followed by major differences in perinatal outcome, 9 but in countries offering nearly universal access to prenatal care, the increased accessibility results in earlier initiation of care and fewer visits.10 The impact on the rate of low birthweight and on infant mortality resulting from different national policies towards prenatal care programmes remains to be fully recognized. In Portugal, every pregnant woman is entitled to free prenatal care, but no information is available regarding factors related to the adequacy of prenatal care or its effect on pregnancy outcome. This study was thus designed to evaluate the role of prenatal care as an independent risk factor for preterm birth and low
Department of Hygiene and Epidemiology, University of Porto Medical School, 4200 Porto, Portugal. HENRIQUE Department
BARROS, Professor of Epidemiology,
Head of
MARGARIDA TAVARES, Lecturer in Epidemiology TERESA RODRIGUES, Lecturer in Epidemiology
Keywords: low birthweight, prenatal care, preterm, risk
Address correspondence to Professor Henrique Barros
© Oxford University Press 1996
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Abstract
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JOURNAL OF PUBLIC HEALTH MEDICINE
birthweight in a sample of Portuguese women delivered at facilities at two different levels.
Participants and methods
Results In the study population, we identified 247 (6-6 per cent) women with inadequate care, 1815 (48-6 per cent) with intermediate care and 1672 (44-8 per cent) who received adequate pregnancy care. Twenty women (06 per cent) had no prenatal visits and 13-6 per cent began care after the first trimester. The level of adequacy of prenatal care according to several maternal characteristics is shown in Table 1, and significant differences were disclosed for every variable assessed. Of the women classified as having inadequate care, 14-2 per cent were adolescents, compared with 5-7 per cent having intermediate care and 3-5 per cent having adequate care; 6-9 per cent were unmarried (compared with 2-2 per cent and 10 per cent); 55-9 per cent used to drink (compared with 48-9 per cent and 41 -2 per cent); and 16-6 per cent were smokers (compared with 80 per cent and 90 per cent) during pregnancy; had higher parity (>4 children, 13-4 per cent; compared with 5-1 per cent and 41 per cent). Also, women with inadequate care more frequently had no pregnancy complications (28-7 per cent), were in the lower class of weight gain (43-3 per cent) or delivered at the Level II institution (798 per cent). Prenatal care and preterm birth Overall, 186 (50 per cent) preterm births occurred in this population, and the mean number (istandard deviation) of prenatal visits was significantly lower for women delivered of a preterm than a term infant (6-8 ± 2-9 versus 8-4 ± 2-8,p < 00001). Compared with mothers who received inadequate prenatal care, a significantly decreased crude risk of preterm was found for those with adequate (OR = 0-20, 95 per cent CI 012-0-32) or intermediate care (OR = 0-35, 95 per cent CI 0-23-0-54). In univariate analysis significant associations with preterm birth were also found for maternal age, marital
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During an 18-month period 2872 women consecutively delivered of a single live infant at a Level II facility (Hospital de Famalicao) were studied. Additionally, during the last four study months, the same procedure was followed at a Level III facility in a large teaching hospital (Hospital de S. Joao, Porto), serving as the referral centre for the first hospital, and 862 women were studied. Within 48-72 h after delivery, every eligible participant answered a questionnaire designed to obtain information on maternal demographic, anthropometric, behavioural, clinical and obstetric characteristics, as well as on the use of prenatal care. Characteristics of the newborn were abstracted from medical records. Quantitative adequacy of prenatal care was classified as inadequate, intermediate or adequate according to Ressner's Adequacy of Prenatal Care Index." This index is based on a combination of the date of the first prenatal care visit, the total number of visits and gestational duration. Social class was determined by the profession of the woman or of her husband if she was a housewife, using the Registrar-General's occupational classification.12 Parity was the number of previous live births. Pregnancy weight gain was defined as the difference between pre- and end-pregnancy weight, as reported by the woman, and categorized as 15 kg, based on previous studies in the same geographical area.13 Pre-pregnancy body mass index was calculated as weight (kg)/height2 (m) and women classified in four groups according to Garrow.14 Alcohol consumption and cigarette smoking during pregnancy were analysed as dichotomous variables. Women were classified as experiencing a pregnancy complication if one or more diagnoses were identified in the medical records or recalled by the woman, regardless of severity or specific relation with pregnancy. Gestational age was the best estimate of the date of the last menstrual period, the ultrasound evaluation or the clinical examination of the newborn. The outcome variables of interest to this study were preterm birth (gestational age < 37 weeks) and low birthweight (weight 4 Pregnancy weight gain (kg)
