PRESENCE OF THE LEMON SIGN IN FETUSES WITH SPINA-BIFIDA AT THE 10-14-WEEK SCAN

In three cases of lumbosacral spina bifida diagnosed at 12, 13 and 14 weeks of gestation there was an associated lemon sign, or scalloping o f the frontal bones, and in one case the fetal nuchal translucency was increased. In a multicenter ultrasound screening study at 10-14 weeks there were 61 972 singleton pregnancies including 29 cases of spina b ifida, none of which was diagnosed at the routine first-trimester scan , but 28 of the 29 cases were detected by ultrasonography at 16-22 wee ks; in one case the diagnosis was missed at the 20-week scan and the d efect was identified at 32 weeks during a scan for localization of the placenta. The fetal nuchal translucency was above the 95th centile in only one of the cases (3.4%). It is possible that the majority of fet uses with spina bifida have a lemon sign in the first trimester, but t he sensitivity of the 10-14-week scan in the diagnosis of spina bifida and the prevalence of the lemon sign at this gestation will only be e stablished by further studies incorporating early systematic examinati on of the head and spine.