In utero environment during development is critical for normal growth and sets the foundations for the health of the individual for life. Exogenous compounds, such as over-the-counter (OTC) analgesics, when consumed during pregnancy by the mother, have the ability to cross the feto-maternal placental interface and reach the developing fetus. OTC analgesics use during pregnancy is often necessary to deal with pregnancy symptoms and other sources of pain or fever. Their abundancy and ease of access without prescription, makes their use difficult to quantify and control. Evidence from several studies using different methodological approaches show conflicting results, questioning the safety of those compounds for the exposed fetus, with associations with adverse offspring health outcomes. This thesis utilised an interdisciplinary approach on the topic. An epidemiological analysis of 151,141 pregnancies assessed associations of OTC analgesic consumption during pregnancy with postnatal offspring health outcomes. Multiple cohorts of human fetal tissue was used to analyse the ability of the fetal liver, placenta and reproductive organs to transport and process those compounds following potential exposure. Results showed a significant association of in utero exposure to OTC analgesics with multiple postnatal health outcomes. The human fetal liver, placenta, testis and ovary express metabolising and transporting machinery to process these compounds. All above organs were able to catalyse paracetamol metabolism after cultured in paracetamol-enriched media in an ex vivo culture system. Observations in this thesis offer an insight on the potential link between in utero exposure to OTC analgesics and postnatal health outcomes.