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COMPARISON OF GESTATIONAL AGE AT DELIVERY BASED ON LAST MENSTRUAL PERIOD AND EARLY ULTRASOUND
Citation:
HOFFMAN, C., L. MESSER, D. A. SAVITZ, K. E. HARTMAN, A. H. HERRING, AND P. MENDOLA. COMPARISON OF GESTATIONAL AGE AT DELIVERY BASED ON LAST MENSTRUAL PERIOD AND EARLY ULTRASOUND. Presented at Society of Pediatric and Perinatal Epidemiologic Research, Seattle, WA, June 20 - 21, 2006.
Description:
Reported date of last menstrual period (LMP) is commonly used to estimate gestational age but may be unreliable if recall is inaccurate or time between menstruation and ovulation differs from the presumed 15-day interval. Early ultrasound is generally a more accurate method than self-report for pregnancy dating. This study compared LMP-based estimates of gestational age at delivery with ultrasound-based estimates and examined whether differences varied by maternal characteristics. Analysis included 1,825 singleton live births to women enrolled in a prospective pregnancy study while planning a pregnancy or newly pregnant (< 12 weeks¿ gestation). Women had a study ultrasound between 6 and 13 weeks¿ gestation and completed a baseline interview. Infant birth date was obtained from medical records, vital records or self-reported. Difference in days between LMP and ultrasound estimates of gestational age was calculated, and proportion of births within categories of difference (<-14, -14 to -8, -7 to +7, +8 to +14 and >+14 days) stratified by maternal characteristics was examined. Proportion of births classified as preterm (<37 weeks), term and postterm (>41 weeks) by methods was also examined. Mean difference between LMP and ultrasound estimates was -0.8 days (standard deviation=8.0), with median discrepancy of 0 days. More births were classified as postterm by LMP (4.0%) than ultrasound (0.7%). Difference in estimates varied significantly by reported certainty in LMP date, maternal age, race, education and marital status. Results indicate LMP generally is a reliable estimate of gestational age given early pregnancy recruitment. Where discrepant, LMP tends to overestimate gestational duration. Discrepancy between estimates may differ by maternal characteristics. This is an abstract of a proposed presentation and does not necessarily reflect EPA policy.