The fetal spine.

Ultrasonography has made it possible to evaluate the fetal spine in utero. Vertebral ossifications are demonstrable by ultrasonography in the early second trimester. Most spinal defects are apparent by 20-22 weeks menstrual age. Early detection of spinal anomalies allows for parental counseling and appropriate obstetrical management. Real-time equipment allows the fetal spine to be examined in parasagittal, transverse and coronal planes. The transverse plane provides the best view of the three ossification centers that form each fetal vertebra. Evaluation of the neural arch ossifications in the transverse view is crucial in detecting spina bifida defects. Ultrasonography of the fetal spine complements the use of alpha-fetoprotein levels in screening for neural tube defects. Examination of the fetal spine is also important in detecting vertebral ossification defects, particularly in cases of short-limbed dwarfs and infants of diabetic mothers.