Introduction: Teenage pregnancy is defined as a pregnancy occurring between ages 10 and 19 (Loredo-Abdlá et al., 2017; Belitzky, 1985; Kaplanoglu et al., 2015), and is associated with increased morbidity and mortality for both mother and child. Several factors have been identified with increased risk of a teenage pregnancy, including incomplete sexual education awareness and increased exposure at a young age. In addition, an earlier onset of sexual intercourse, or coitarche, has been linked to a higher risk of teenage pregnancy. Early menarche, defined as first menstruation before the age of 12 has been previously identified as a risk factor for an earlier coitarche, possibly linking an early menarche with a higher incidence of teenage pregnancy. This study aims to compare and determine the relationship between the incidence of teenage pregnancy with early menarche and coitarche in a low income setting. Design, Setting, Participants, Interventions, Main Outcome, Measures: A cross sectional review of electronic records of women admitted for delivery in a second level center in northeastern Mexico, being a low-income setting, where 814 teenage and 1474 adult mothers were included. Results: Primigravid teenagers had earlier menarche and coitarche than adult counterparts and opted for postpartum contraception more frequently. Linear regression analysis revealed significant unadjusted beta coefficients between age at first pregnancy and coitarche (0.839) and menarche (0.362). Menarche and coitarche had a significant linear regression association of 0.395. Conclusion: We found amongst primigravid patients that teenagers had earlier menarche and coitarche than adults, which in turn correlated to their age at their first pregnancy.
