Estimation of gestational age by amniocentesis

Area of Science:

• Obstetrics and Gynecology
• Prenatal Diagnostics
• Fetal Development

Background:

• Accurate estimation of gestational age is crucial for optimal pregnancy management and delivery timing.
• Traditional methods for dating pregnancies include ultrasound and assessment of fetal growth parameters.

Purpose of the Study:

• To compare the accuracy of gestational age estimation using amniotic fluid cytology and creatinine levels with early ultrasound biparietal diameter (BPD) measurements.
• To evaluate the reliability of amniotic fluid tests for dating pregnancies, particularly in cases of uncertain dates or when early ultrasound is not performed.

Main Methods:

• Gestational age estimation by plotting the percentage of lipid-carrying cells (amniotic fluid cytology) and amniotic fluid creatinine concentration.
• Comparison of amniotic fluid test dating with early ultrasound (biparietal diameter, BPD) measurements in 53 samples from 48 pregnancies.

Main Results:

• A high correlation (r = 0.72) was observed between gestational age estimated by amniotic fluid tests and early BPD measurements.
• The two methods agreed within 2 weeks in 94% of cases.
• Amniotic fluid tests overestimated gestational age compared to BPD in one third of infants with low birth weight for age, potentially due to growth retardation effects.

Conclusions:

• Amniotic fluid tests provide a reliable method for estimating gestational age, especially when early ultrasound is not available or dates are uncertain.
• Discrepancies in cases of intrauterine growth retardation may be influenced by combined effects on BPD and accelerated maturation.
• This method is particularly useful for guiding decisions prior to elective delivery in pregnancies with uncertain dating.