The accurate ascertainment of any pregnancy, as well as the determination of the start of any pregnancy, are integral to improving maternal health outcomes and assessing drug exposure. Drug safety and pregnancy outcomes studies utilize health claims, but there are no published pregnancy algorithms that are based on ICD-10 CM/PCS. Currently, there is no unified approach in identifying pregnancies using the current coding system. Using the HealthCore Integrated Research Database (HIRD), we have developed a pregnancy method that 1) ascertain end of pregnancy events for both birth/delivery and termination, 2) estimate their gestational age, and 3) distinguish multiple pregnancies. The assumptions and criteria of our proposed method were tested and refined using the HIRD database, as well as through numerous patients/claims profile reviews. A future validation study would be useful in providing an estimate of the accuracy of our method.