The relationship between antenatal care and preterm birth: the importance of content of care.

Background: Antenatal care can play an important role in the prevention of preterm birth. Evaluation of antenatal care is usually based on the number of visits rather than the content of care, using tools such as the Adequacy of Prenatal Care Use index. This article presents an analysis of the relation between specific elements of antenatal care and the risk of preterm birth compared with considering the number of visits only.
Methods: A prospective cohort study was conducted in the Brussels Metropolitan Region. In all, 333 women were consecutively recruited at the beginning of their antenatal care trajectory and followed until birth. Information on timing and content for every visit was recorded by structured interview. A new tool was developed to measure the antenatal care trajectory, which included Content and Timing of care in Pregnancy (CTP). Odds ratios (OR) (adjusted and unadjusted) for preterm birth were calculated for the Adequacy of Prenatal Care Use and CTP model.
Results: The number of visits alone was not associated with preterm birth. In contrast, a significant association was found between the content and timing of care and preterm birth. Compared with the CTP lowest ('inadequate') category, women in the CTP 'sufficient' (OR 0.30; 95% CI 0.09-0.94) and CTP 'appropriate' (OR 0.21; 95% CI 0.06-0.68) category had a lower risk.
Conclusions: This study suggests that measurement of the content and timing of care of antenatal care using the new CTP tool is a better assessment of the risk of preterm birth than assessment of the number of antenatal visits alone.