Estimation of gestational age using trans-cerebellar diameter: a sonographic study of a cohort of healthy pregnant women of Igbo ethnic origin in a suburb of Lagos, southwest Nigeria

Abstract

Aim: To use a sonographic method to determine the usefulness of trans-cerebellar diameter (TCD) as an independent estimator of gestational age (GA).

Methods: A convenience sample of 257 healthy pregnant women of Igbo ethnic origin with singleton normal pregnancy whose GA ranged from 16 to 40 weeks were examined. GA was calculated from the date of onset of the last menstrual period (LMP) and was used as the standard criterion, while the biparietal diameter (BPD), head circumference (HC), abdominal circumference (AC), and femur length (FL) were used to estimate GA. TCD was measured and employed to derive regression models utilized to assess GA.

Results: The mean TCD was 32.0 ± 11.6 mm; TCD had a strong positive linear relationship with GA (R = 0.988; R² = 0. 975; P = < 0.001). The GA that was estimated using regression models, which were derived using the sonographically measured TCD, was closer to the actual GA in the second and third trimesters of pregnancy than the GA estimated using other fetal parameters.

Conclusion: In a population of healthy pregnant women of Igbo ethnic origin living in Oshodi, Lagos State, Nigeria, the sonographically measured TCD was more accurate as a single estimator of GA than BPD, HC, AC, and FL in the late stages of pregnancy. Subject to further validation, the nomograms derived using TCD proposed in the present study could be used as reliable GA estimators in the late stages of pregnancy among women who are unsure of the date of onset of their LMP.

Keywords: Estimation; Gestational age; Trans-cerebellar diameter; Ultrasonography.

Fig. 1

Fetal skull showing TCD measurement in a fetus of 21 weeks ± 3 days’ gestation. The line AB (between cross heads) represents TCD

Fig. 2

A histogram of regression standardized residual plot. Note the near symmetry of both halves of the superposed normal curve normality of TCD data

Fig. 3

A P–P plot showing the relationship between the observed and expected values in the combined trimester. P–P probability–probability, Prob. probability

Fig. 4

a The relationship between trans-cerebellar diameter and gestational age in the second trimester. Press presumed. b The relationship between trans-cerebellar diameter and gestational age in the third trimester. c The relationship between trans-cerebellar diameter and gestational age in the combined trimester

Fig. 5

a The relationship between GA and BPD. b The relationship between GA and HC. c The relationship between GA and FL. d The relationship between GA and AC