Proper decisions regarding presumed preterm labor or postdate pregnancies are only possible when gestational age is accurately estimated.
Timed ovulation, either by basal body temperature recording or semiquantitative assessment of luteinizing hormone surge, predicts gestational age within ±4 to 6 days.
Ovulation induction with agents such as clomiphene citrate and Pergonal, also accurately predicts gestational age.
In the past gestational age was established by a combination of the historical information and the physical examination.
Reliance was placed on the menstrual history and the maternal sensation of fetal movement (“quickening”).
In another report, even among women with known LMP, neonatal age assessment differed markedly from that assigned by certain menstrual dates in 15%.