Evaluation of Foetal Cardiothoracic Ratio in Normal Pregnancy: Correlation with Gestational Age, Foetal Weight and Established Nomogram

Background: An important sign of congenital heart disease (CHD), myocardial dysfunction and foetal congestive cardiac failure is cardiomegaly, which is detected using the assessment of the cardiothoracic (CT) ratio. Objective: To evaluate the foetal CT ratio and its relationship with gestational age in the second half of pregnancy, and produce nomograms for the foetal CT ratio. Subjects and Methods: This descriptive, cross‐sectional study enrolled women with a normal pregnancy in their second and third trimesters at the two tertiary health facilities, one secondary facility and one radiodiagnostic facility in Bayelsa State, Nigeria. The study was conducted from April–December 2022. Pearson's correlation and logistic regression analyses were used to assess the relationship and correlation between the CT ratio, gestational age, and estimated foetal weight. The p<0.05 at 95%CI level of significance was set. Results: The mean bi-parietal diameter estimated foetal weight and CT diameter ratio was 66.5 ± 18.3 mm, 1.24 ± 0.87 kg and 0.46 ± 0.02 cm respectively. The foetal CT ratio correlates very strongly with estimated gestational age (ɼ = 0.98; p – 0.001), bi-parietal diameter (ɼ = 0.96; p – 0.001), estimated foetal weight (ɼ = 0.92; p – 0.001), Maternal age (ɼ = 0.36; p – 0.001), maternal weight (ɼ = 0.19; p – 0.001) and maternal height (ɼ = 0.20; p – 0.001). Conclusion: We have demonstrated that there does exist a very strong correlation between the foetal cardiothoracic ratio and the foetal gestational age, biparietal diameter and foetal weight, which slightly, but steadily increased throughout pregnancy.