Pregnant women are heavily underrepresented in clinical trials as it would be unethical to conduct a human trial in which the potential outcome is a birth defect in the offspring. Between 2000-2010, over 97% of clinically approved drugs in the US had an undetermined teratogenic risk (the risk of foetal abnormality from exposure to a drug) or adverse developmental effect in human pregnancy . This presents a significant problem as there are a range of chronic conditions that require ongoing treatment, such as epilepsy, hypertension, auto-immune disorders or psychiatric disorders that may precede or develop during the pregnancy. This can mean women are deprived of medication due to clinical reservations or are prescribed medications that cause potential harm to the offspring. Given the inability to perform RCTs, the harmonisation of pharmacoepidemiological and genetic data is an alternative way to evaluate the potential risks currently associated with continuing medications to provide reliable information for clinicians and patients. The main objective of this PhD is to establish reliable evidence for the intrauterine exposure of prescription drugs on the mother and offspring by triangulating evidence from the Clinical Practice Research Datalink (CPRD), The Norwegian Mother, Father and Child Cohort Study (MoBa) and ALSPAC.