[Adequacy of prenatal care and birthweight: a systematic review].

This was a systematic literature review on publications in which prenatal care was investigated as a predictive factor for birthweight. The MEDLINE, Cochrane Library, and SciELO databases were searched using a combination of the following uniterms: "prenatal care", "antenatal care", "quality", "adequacy", "birthweight", and "low birthweight". Twenty-five studies were found: seventeen had a cross-sectional design, in addition to four cohort studies, three case-control studies, and one randomized trial. The adequacy indicators related to utilization (quantitative measures) and content of prenatal care (process or qualitative indicators). Most authors employed quantitative indicators, mainly the Kessner Index and the Adequacy of Prenatal Care Utilization Index. Qualitative criteria were used in only two studies. Most of the cross-sectional studies found a protective effect of prenatal care against low birthweight, whereas results of studies with other designs were conflicting. This review's findings highlight that the impact of prenatal care on birthweight is not unequivocal, mainly due to the effect of self-selection bias. Randomized trials are needed to elucidate such a relationship.