Normative references of fetal chest circumference in a Nigerian population

ABSTRACT

A linear relationship between gestational age and fetal thoracic size has been observed, with growth occurring at a regular rate from 16 to 40 weeks.Objective: To determine the fetal chest circumference in normal late second and third-trimester pregnancies in a Nigerian population.Materials and Methods: This was a descriptive cross-sectional study carried out on gravid women with normal singleton pregnancies at 22 ­ 38 weeks gestational age. We recruited 440 eligible gravid women. The fetal gestational age was estimated from the last menstrual period and an early first trimester ultrasound report (< 10 weeks). The fetal chest circumference was measured on an axial view of the fetal chest after ensuring adequate visualisation of the four cardiac chambers, both fetal lungs and ribs. The other fetal biometric parameters were determined using the previously established guidelines. Descriptive statistics, Pearson's correlation, and regression analysis were used as appropriate. Statistical tests were considered significant at P ≤ 0.05.Results: The mean age of the subjects was 29.8 ± 4.6 years (range = 18-45 years). The chest circumference of the fetuses ranged from 16.56 ± 0.29 cm to 30.87 ± 6.88 cm. The fetal chest circumferences increased with advancing gestational age (16.56 ± 0.29 cm at 22 weeks to 30.87 ± 6.88 cm at 37 weeks gestational age). There was strong positive correlation between chest circumference and menstrual gestational age (r=0.85, p=<0.0001), biparietal diameter (r=0.88, p<0.0001), abdominal circumference (r=0.90, p<0.0001) and fetal length (r=0.88, p<0.0001).Conclusion: The fetal chest circumference grew as the pregnancy progressed. There was a positive linear correlation between fetal chest circumference and menstrual gestational age as well as the other fetal biometric parameters.