The Normal Fetal Cephalic Index in the Second and Third Trimesters of Pregnancy

Antenatal Ultrasound Imaging for Analysis of Human Craniosynostosis

The cranial sutures can be imaged sonographically in the fetus as early as the end of the first trimester; however, fetal position and maternal body habitus can present significant challenges to clear visualization. Antenatal identification of craniosynostosis is important for delivery planning, and there are a number of available ultrasound techniques and imaging signs to assist with accurate diagnosis of both single suture craniosynostosis and syndromic multisutural fusions.

Sonographic indicators of isolated fetal sagittal craniosynostosis during pregnancy

INTRODUCTION

The antenatal diagnosis of sagittal craniosynostosis can be challenging, but there are several published papers describing a traumatic outcome to both the affected fetus and the mother during delivery of a scaphocephalic child. The antenatal imaging from affected children was collected along with the mother's obstetric history. The aim of this study was to identify antenatal ultrasound features that may assist the diagnosis of sagittal synostosis before birth, to enable appropriate delivery planning and avoid both maternal and fetal trauma during birth.

METHODS

Antenatal ultrasound scans in both the second and third trimesters were traced for 36 children with sagittal synostosis. The initially diagnostic CT scans were also sourced. A delivery history was collected from the hospital case notes where available.

RESULTS

The affected group showed a statistically significant reduction in cephalic index during the second half of pregnancy compared with the normal population which became slightly more brachycephalic (P = 0.001). Regression analysis showed an average reduction in cephalic index of 0.57 units per month. There was also a much higher rate of malpresentation and surgical deliveries in the affected group than the normal population. There was a relationship between sagittal craniosynostosis and breech presentation and an associated higher rate of surgical deliveries.

CONCLUSION

It is possible to detect sagittal synostosis in the third trimester of pregnancy which may assist with delivery planning.