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COMPARISON OF GESTATIONAL AGE AT BIRTH BASED ON LAST MENSTRUAL PERIOD AND ULTRASOUND DURING THE FIRST TRIMESTER
Citation:
HOFFMAN, C., L. C. MESSER, P. MENDOLA, D. A. SAVITZ, A. H. HERRING, AND K. E. HARTMAN. COMPARISON OF GESTATIONAL AGE AT BIRTH BASED ON LAST MENSTRUAL PERIOD AND ULTRASOUND DURING THE FIRST TRIMESTER. PAEDIATRIC AND PERINATAL EPIDEMIOLOGY. Blackwell Publishing, Malden, MA, 22(6):587-596, (2008).
Impact/Purpose:
The authors compared first trimester report of LMP and first trimester ultrasound for estimating GA at birth and examined whether disagreement between estimates varied by maternal and infant characteristics.
Description:
Reported last menstrual period (LMP) is commonly used to estimate gestational age (GA) but may be unreliable. Ultrasound in the first trimester is generally considered a highly accurate method of pregnancy dating. The authors compared first trimester report of LMP and first trimester ultrasound for estimating GA at birth and examined whether disagreement between estimates varied by maternal and infant characteristics. Analyses included 1,867 singleton live births to women enrolled in a prospective pregnancy cohort. Authors computed the difference between LMP and ultrasound GA estimates (GA difference) and examined the proportion of births within categories of GA difference stratified by maternal and infant characteristics. The proportion of births classified as preterm, term and postterm by pregnancy dating methods was also examined. LMP-based estimates were 0.8 days (standard deviation=8.0, median=0) longer on average than ultrasound estimates. LMP classified more births as postterm than ultrasound (4.0% versus 0.7%) but the proportions classified as preterm were similar (10.0% versus 8.9%). GA difference was greater among young women, non-Hispanic Black and Hispanic women, less educated women, women of non-optimal body weight and mothers of low birth weight infants. Results indicate first trimester report of LMP is a reliable estimate of GA.
