Fetal open spina bifida: a natural history of disease progression in utero.

OBJECTIVE

To determine the natural history of the prenatal development of ventriculomegaly and talipes in fetuses with open spina bifida.

STUDY DESIGN

All fetuses with isolated open spina bifida and managed at our center between January 1996 and March 2000 were retrospectively evaluated. Ultrasonographic images and reports were reviewed from examinations performed every 3 to 4 weeks from the time of diagnosis to delivery for lesion level and type, ventriculomegaly (defined as an atrial width of > or =10 mm), and lower extremity appearance.

RESULTS

Of the 53 pregnancies identified, 20 (38%) were electively terminated. In the 33 ongoing gestations, the lesions ranged from lower thoracic to sacral; 79% were characterized as meningomyeloceles and 21% as myeloschises. Fifty-five percent (n = 18) had ventriculomegaly at diagnosis (early onset, mean gestational age at diagnosis 22 +/- 5 weeks), 33% (n = 11) subsequently developed ventriculomegaly (late onset, mean 29 +/- 6 weeks), and 12% (n = 4) had normal ventricle size at the last sonogram before birth (mean 38 +/- 1 weeks). The ventricular size prior to delivery was significantly smaller with late-onset ventriculomegaly than with early-onset: 15 +/- 4 mm versus 28 +/- 10 mm, (p = 0.001). Only 6% (n = 2) had talipes at the initial sonogram, and 18% (n = 6) were subsequently determined to have talipes (mean 30 +/- 6 weeks).

CONCLUSION

Most fetuses with open spina bifida develop ventriculomegaly, and the majority do so by 21 weeks' gestation. Fetuses that develop ventriculomegaly later in gestation have less severe ventricular dilation at birth. In contrast, a minority of fetuses have congenital talipes, and because most cases develop after 20 weeks, they are not predicted by early midtrimester sonographic evaluation.