Frontal Lobe Development in Fetuses With Congenital Heart Disease and Its Relation to Expected Brain Arterial Oxygen Saturation

Objectives To compare fetal head growth and assess differences in fetal frontal lobe development between fetuses with congenital heart disease (CHD) and normal fetuses. To investigate the association between in utero fetal frontal lobe growth and the expected level of cerebral arterial oxygen saturation (SaO 2 ). Methods This was a retrospective study, including 634 fetuses diagnosed with CHD and 677 normal fetuses. All these fetuses underwent fetal ultrasound scans after the 19th gestational week from January 2018 to June 2024. Fetuses with CHD were categorized into 3 groups based on the expected level of cerebral arterial SaO 2 : normal, mildly to moderately reduced, and severely reduced. CHD cases were also categorized into isolated CHD and non‐isolated CHD, as well as classified based on anatomical subtypes. To assess frontal lobe growth and brain development across gestational ages, we measured biparietal diameter (BPD), head circumference (HC), frontal lobe anteroposterior diameter (FAPD), and occipitofrontal diameter (OFD), and then calculated the FAPD/OFD ratio. The BPD, HC, FAPD, and FAPD/OFD ratio were then compared between the CHD subtypes and the normal group. Results In total, 1196 individual ultrasound scans from 634 CHD fetuses and 3538 from 677 controls after the 19th gestationalweek were available for measurement, respectively. Fetuses with CHD were found to have a slightly smaller BPD, HC, and FAPD than normal fetuses, and the reductions decreased with the advancing gestational age. For the FAPD/OFD ratio, the value showed a consistent lower trend in the CHD group than in the control group, independent of gestational age and HC, with a progressive reduction as cerebral arterial SaO 2 worsened in the CHD group ( P < .001). Isolated and non‐isolated CHD subgroups did not show any significant difference in the FAPD/OFD ratio ( P = .480). Conclusion Fetuses with CHD exhibit impaired frontal regional growth, which may be associated with hypoxia. The cardiac‐induced hemodynamic changes may play a critical role in influencing neurodevelopment, particularly affecting frontal lobe growth. The FAPD/OFD ratio could be a simple and reliable tool to evaluate the development of the frontal lobe.