The appropriate interpretation of monitored fetal growth throughout pregnancy in individual patients and populations is dependent upon the availability of adequate standards. There is no adequate standard of fetal weight throughout pregnancy that is suitable for patients in the U.S.A. To determine such a standard for infants delivered at about sea level the 10th, 25th, 50th, 75th, and 90th percentiles of fetal weight for each menstrual week of gestation were calculated from 430 fetuses at 8 to 20 menstrual weeks' gestation aborted with prostaglandins and from 30,772 liveborn infants delivered of patients at 21 to 44 menstrual weeks' gestation. Median fetal crown-to-rump lengths and crown-to-heel lengths were derived from measurements of 496 aborted fetuses of 8 to 21 weeks' gestation. Fetal weight correction factors for parity, race (socioeconomic status), and fetal sex were calculated. The derived fetal growth curves are useful for clinical, public health, and investigational purposes.