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Effect of various dating formulae on sonographic estimation of gestational age in extremely preterm infants
M Simic1, I Amer-Wåhlin, K Maršál
1Department of Women's and Children's Health, Karolinska Institutet, Stockholm, Sweden. marija.simic@karolinska.se
Insights
Estimating gestational age (GA) for extremely preterm infants using different formulas significantly impacts delivery date predictions. This variation may affect clinical management decisions for these vulnerable infants.
Area of Science:
- Obstetrics and Gynecology
- Neonatal Medicine
- Medical Statistics
Background:
- Gestational age (GA) is a critical factor in obstetrics, influencing fetal development and delivery timing.
- Accurate prediction of the date of delivery is typically based on fetal measurements obtained via ultrasound.
- Estimating GA for extremely preterm infants presents unique challenges due to developmental variations.
Purpose of the Study:
- To evaluate the impact of three distinct dating formulas on gestational age estimation in extremely preterm infants.
- To compare GA estimates derived from different formulas against clinically reported GA and last menstrual period (LMP)-based GA.
Main Methods:
- Analysis of 513 infants delivered before 27 weeks gestation from the Swedish national population study (EXPRESS).
- Application of Persson & Weldner, Hadlock, and Mul dating formulas using biparietal diameter and femur length measurements.
- Comparison of formula-derived GA estimates with clinically recorded GA and LMP-based GA.
Main Results:
- The Persson & Weldner formula closely matched the reported GA (173.3 vs. 173.2 days).
- LMP, Hadlock, and Mul formulas yielded higher mean GA estimates (176.8, 175.3, and 175.6 days, respectively).
- Significant differences were observed between Hadlock/Mul formulas and the Persson & Weldner formula (P < 10(-6)), potentially reclassifying nearly half of 22-week pregnancies to 23 weeks or more.
Conclusions:
- The choice of dating formula significantly influences gestational age estimation in extremely preterm infants.
- Discrepancies in GA estimation can have substantial implications for the clinical management of extremely preterm fetuses and neonates.
Objectives:
Gestational age (GA) is one of the most important obstetric factors and prediction of date of delivery is usually based on ultrasonographic fetal measurements. Our aim was to determine whether applying three different dating formulae to a cohort of extremely preterm infants influenced the estimation of their GA.
Methods:
This was a study of 513 infants delivered before 27 gestational weeks, included in a Swedish national population study (EXPRESS), with information available on mid-trimester ultrasonographically measured biparietal diameter and femur length. We applied using these parameters three dating formulae, the Persson & Weldner formula, commonly used in Sweden, the Hadlock formula and the Mul formula, and compared their GA estimates to the clinically reported GA (recorded at delivery) and the last menstrual period (LMP)-based GA.
Results:
The mean reported GA was 173.2 days, corresponding well to the GA according to the Persson & Weldner dating formula (173.3). The mean GA according to LMP, the Hadlock formula and the Mul formula were 176.8, 175.3 and 175.6 days, respectively. The Hadlock and Mul GA estimates differed significantly from that based on the Persson & Weldner formula (both P-values < 10(-6)). Among 68 pregnancies with a reported duration of 22 weeks, 33 (49%) had a duration of 23 weeks or more when GA was calculated according to LMP and 22 (32%) when GA was calculated according to the Hadlock formula.
Conclusion:
Estimated GA among infants delivered before 27 gestational weeks varied significantly depending on the dating formula used to calculate the estimated date of delivery; this might influence the clinical management of extremely preterm fetuses and infants.
