Sonographic correlation of foetal neck circumference and area with gestational age among pregnant women in Port Harcourt, Nigeria

Abstract

The purpose of this study was to create a reference range nomogram of foetal neck circumference (FNC) and foetal neck area (FNA) in a Nigerian population using polynomial regression models. This cross-sectional study involved 723 pregnant women between 14 and 40 weeks of gestation. Axial measurements of the FNC and FNA were obtained in three measurements and the mean taken as the final value and the 5th, 50th and 95th percentiles for each foetal gestational age (FGA) were calculated. FNC and FNA correlated strongly with FGA, biparietal diameter, abdominal circumference, head circumference, and femoral length. Cubic models fitted the FNC vs FGA, and FNA vs. FGA values, and the mathematical relationships are given as: [Formula: see text] [Formula: see text] [Formula: see text]. Nomograms of FNC and FNA are thus generated. Impact statement The foetal neck circumference (FNC) and foetal neck area (FNA) can serve as predictors of foetal gestational age (FGA) since they correlate strongly and positively with FGA and known biometric parameters. The measurements obtained vary with the population studied. This study provides a nomogram of the FNA and FNC for an African population. The values correlate with that of the Caucasian population up to 32 weeks FGA. Interestingly, FNA and FNC measurements demonstrate high correlation but poor agreement in measurements between sonographers. Even though FNA and FNC could be used as predictors of foetal gestational age, the measurements vary significantly between sonographers. This is attributable to the difficulty in obtaining a satisfactory axial view of foetal neck, which is dependent on foetal presentation.

Nomograms of the fetal neck circumference and area

“…[9] When Abonyi et al also noticed the difference in reference ranges after 30-32 weeks of gestation, they argued that it was caused by the different populations rather than technological improvement. [27] In general, the reference ranges in our study show similarity with the values found by Sherer et al during entire pregnancy period.…”

“…Moreover, evaluating many parameters to calculate gestational age will increase the reliability rather than evaluating a single sonographic parameter. [24,25] The high correlation between the week of gestation and FNC and FNA measurements was shown in the studies of Hata et al in 1988, Sherer et al in 2007 andAbonyi et al in 2017. [9,26,27] In our study, FNC increased from 4.91±0.72 at 14 weeks of gestation to 17.52±2.11 at 40 weeks of gestation.…”

“…Hata et al [26] published these measurements in their study in 1988 and these measurements have become simpler with today's technology. In the literature, the interjudge reliability was evaluated only in the study of Abonyi et al [27] and the authors found a weak conformity among the operators. By now, there are three studies conducted with FNC and FNA nomograms.…”

Sonographic Assessment of Fetal Neck Circumference (NC) As a Predictor of Gestational Age

“…We compared data from this study to other similar studies [12,21,22] from different races (Caucasian and African), using their respective centiles. A comparative study of the 50th centile was carried out to rule out any significant difference in values.…”

“…This variation is likely to be present among ethnic groups in Africa because genetically individuals are unique as a result of inheritance, geographical location and environmental interactions [18,20]. Consequently, there was a need to establish nomograms for this population without prejudice to a published study conducted in a diverse population whose frame and size are disparate to ours [21]. The study aimed to establish fetal NC nomogram as a predictor of GA estimation in this population and also verify the influence of ethnicity on nomograms.…”