Li Q, Andrade SE, Cooper WO, Davis RL, Dublin S, Hammad TA, Pawloski PA, Pinheiro SP, Raebel MA, Scott PE, Smith DH, Dashevsky I, Haffenreffer K, Johnson KE, Toh S. Validation of an algorithm to estimate gestational age in electronic health plan databases. Pharmacoepidemiol Drug Saf. 2013 May; 22(5):524-32.