Objective: To determine conditions that may explain the failure to attend the programmed prenatal control appointments (cPn), and assessing whether eliminating the access barriers improves the health conditions of pregnant women. Methodology: We performed a mixed design prospective cohort study in several stages. Results: The main access barrier that caused failures to attend was difficulties to pay for transportation. By giving transportation subsidies, the failures to attend to the appointments were reduced by 87%. The health determinants associated with a higher probability of having perinatal complications were: low socio-economic status, distance from their residence to the attention site, and a high score in the bio-psychosocial risk scale. Additionally, factors like tertiary education and economic support in charge of the man head of the household were associated with a decrease in the risk of maternal-fetal complications. Conclusions: the economic, socio-cultural and geographical barriers ignored by the Colombian health system affect access to the cPn.