Validity of pre and post-term birth rates based on the date of last menstrual period compared to early obstetric ultrasonography.

Maria Nilza Lima Medeiros,Rosângela Lucena Fernandes Batista,Fabrício José Alencar Mesquita,Marco Antonio Barbieri,Vanda Maria Ferreira Simões,Heloisa Bettiol,Nádia Carenina Nunes Cavalcante,Viviane Cunha Cardoso,Antônio Augusto Moura Da Silva,Ricardo De Carvalho Cavalli

doi:10.1590/0102-311x00121514

Maria Nilza Lima Medeiros, Rosângela Lucena Fernandes Batista + Show 8 more

Open Access

https://doi.org/10.1590/0102-311x00121514

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Abstract

The aim of this study was to assess the validity of the last menstrual period (LMP) estimate in determining pre and post-term birth rates, in a prenatal cohort from two Brazilian cities, São Luís and Ribeirão Preto. Pregnant women with a single fetus and less than 20 weeks' gestation by obstetric ultrasonography who received prenatal care in 2010 and 2011 were included. The LMP was obtained on two occasions (at 22-25 weeks gestation and after birth). The sensitivity of LMP obtained prenatally to estimate the preterm birth rate was 65.6% in São Luís and 78.7% in Ribeirão Preto and the positive predictive value was 57.3% in São Luís and 73.3% in Ribeirão Preto. LMP errors in identifying preterm birth were lower in the more developed city, Ribeirão Preto. The sensitivity and positive predictive value of LMP for the estimate of the post-term birth rate was very low and tended to overestimate it. LMP can be used with some errors to identify the preterm birth rate when obstetric ultrasonography is not available, but is not suitable for predicting post-term birth.

Highlights

The date of last menstrual period (LMP) has been the method most frequently used to estimate gestational age in epidemiological studies
The preterm birth rates determined by both the last menstrual period obtained during the prenatal period and the LMP obtained at delivery were usually higher than those obtained by obstetric ultrasonography in both cities
Excellent agreement regarding preterm birth was observed between last menstrual period obtained during the prenatal period and LMP obtained at birth, both in São Luís and Ribeirão Preto

Summary

Introduction

The date of last menstrual period (LMP) has been the method most frequently used to estimate gestational age in epidemiological studies. Its accuracy has been questioned because it assumes that women have regular menstrual cycles and that the self-reported information about LMP is precise [1,2]. Errors in gestational age estimate based on LMP are greater in populations of lower educational levels 5. On this basis, early obstetric ultrasonography performed during the first trimester of gestation has become the gold standard for the estimate of gestational age based on skull-rump length separately or in combination with last menstrual period 3. Most of the available studies have been conducted in high-income countries [1,2], with little information available for low and middle-income countries 5, in which errors of gestational age classification based on LMP must be greater

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