Why do aboriginal newborns weigh less? Gestational age at delivery: estimation, distribution and determinants

Area of Science:

• Maternal-fetal medicine
• Perinatal epidemiology
• Indigenous health research

Background:

• Accurate gestational age estimation is crucial for perinatal care.
• Previous studies suggest potential differences in fetal growth and gestation length between Indigenous and non-Indigenous populations.
• Standardized ultrasound dating protocols are widely used, but their applicability across diverse populations requires validation.

Purpose of the Study:

• To compare ultrasound-derived gestational age estimates with last menstrual period (LMP) dates in Western Australian Aboriginal pregnancies.
• To compare gestational age distributions of Aboriginal neonates with Caucasian neonates using Caucasian ultrasound standards.
• To identify determinants of gestational age at delivery for Aboriginal neonates.

Main Methods:

• Review of 1,301 Western Australian singleton Aboriginal pregnancies.
• Ultrasound fetometry used for dating before 24 weeks, applying Caucasian standards.
• Comparison of ultrasound-derived vs. LMP-derived gestational age estimates.
• Analysis of gestational age distributions for full-blood vs. part-blood Aboriginal neonates and comparison with Caucasian neonates.
• Investigation of factors influencing gestational age at delivery.

Main Results:

• Ultrasound estimates were statistically, but not clinically, shorter than LMP-derived estimates (mean difference = 0.4 weeks).
• Aboriginal gestations were shorter than Caucasian gestations by 1-2 weeks (mode/median).
• Factors like antepartum hemorrhage, congenital anomalies, and certain maternal conditions explained only a small portion of the gestation shortening; Aboriginality (full-blood vs. part-blood) did not significantly impact this.
• Caucasian fetometry standards provided acceptable gestational age estimates for Aboriginal pregnancies.

Conclusions:

• Caucasian ultrasound fetometry standards are suitable for dating Aboriginal pregnancies before 24 weeks.
• Aboriginal gestations tend to be shorter than Caucasian gestations.
• The observed difference in gestation length is not fully explained by recorded medical factors, suggesting potential contributions from socioeconomic determinants.