Dating gestational age by last menstrual period, symphysis-fundal height, and ultrasound in urban Pakistan

Abstract

Objective To compare the accuracy of the reported date of the last menstrual period (LMP) with that of symphysis-fundal height (SFH) in the estimation of gestational age (GA), using an ultrasound (US) scan as reference. Methods Gestational age was concurrently assessed by the 3 methods in this prospective, population-based, pregnancy-outcome study conducted in Hyderabad, Pakistan, from June 18, 2003, through August 31, 2005, with 1128 women between 20 and 26 weeks of a singleton pregnancy. Results The mean GA was less by ultrasound than by SFH measurement or the reported LMP, and the mean differences with the US result were statistically significant ( P < 0.001 for both). At delivery, about 75% of the GA values estimated by SFH measurement were within 7 days and almost 91% were within 14 days of the estimation by ultrasound, compared with 65% and 82% for the GA estimated by the reported LMP. Moreover, using the US as reference, the SFH correctly classified 84% of the term, 68% of the preterm, and 86% of the post-term deliveries (weighted κ = 0.58) compared with the corresponding 79%, 61%, and 55% predicted by the reported LMP (weighted κ = 0.44). Conclusion The SFH measurement was found to be more accurate than the reported LMP as a tool to estimate GA and therefore date of delivery, but neither were as accurate as a US scan.