Determining gestational age based on information from the Birth in Brazil study

Area of Science:

• Obstetrics and Gynecology
• Public Health Research
• Biostatistics

Background:

• Accurate estimation of gestational age is crucial for maternal and neonatal health outcomes.
• Existing methods for estimating gestational age in Brazil, such as the last menstrual period, may have limitations.
• The Birth in Brazil survey provides a large dataset for evaluating these estimation methods.

Purpose of the Study:

• To assess the validity of different measures for estimating gestational age at birth.
• To propose an algorithm for improved gestational age at birth estimates within the Birth in Brazil survey.
• To compare the accuracy of ultrasound-based measures and last menstrual period-based measures.

Main Methods:

• Utilized early ultrasound imaging (7-20 weeks gestation) as the reference standard.
• Analyzed data from 23,940 postpartum women in the 2011-2012 Birth in Brazil survey.
• Stratified analyses by maternity care payment (public vs. private) to assess potential disparities.

Main Results:

• Ultrasound-based gestational age at admission showed substantial intraclass correlation coefficients (0.95 public, 0.94 private).
• Gestational age reported by postpartum women also demonstrated high correlation (0.90 public, 0.88 private).
• Last menstrual period-based measures exhibited lower intraclass correlation coefficients compared to ultrasound and interview data.

Conclusions:

• Early ultrasound imaging is a highly reliable method for estimating gestational age in the Brazilian context.
• Gestational age reported by postpartum women is a valuable secondary measure.
• Caution is advised when relying solely on the last menstrual period for gestational age estimation in Brazil.