Send to

Choose Destination
See comment in PubMed Commons below
Paediatr Perinat Epidemiol. 2008 Nov;22(6):587-96. doi: 10.1111/j.1365-3016.2008.00965.x.

Comparison of gestational age at birth based on last menstrual period and ultrasound during the first trimester.

Author information

  • 1Department of Epidemiology, University of North Carolina at Chapel Hill, NC, USA.


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 1867 singleton livebirths to women enrolled in a prospective pregnancy cohort. The 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 post-term 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 post-term than ultrasound (4.0% vs. 0.7%). GA difference was greater among young women, non-Hispanic Black and Hispanic women, women of non-optimal body weight and mothers of low-birthweight infants. Results indicate first trimester report of LMP reasonably approximates gestational age obtained from first trimester ultrasound, but the degree of discrepancy between estimates varies by important maternal characteristics.

[PubMed - indexed for MEDLINE]
PubMed Commons home

PubMed Commons

How to join PubMed Commons

    Supplemental Content

    Full text links

    Icon for Wiley
    Loading ...
    Support Center