Nomogram for estimating an individual's risk of having a fetus with open spina bifida.

A nomogram indicating the risk of having a fetus with open spina bifida in relation to a particular maternal serum and amniotic fluid alpha-fetoprotein (AFP) level is described. The nomogram is designed for counselling patients with borderline amniotic fluid AFP results, who on average are only marginally at risk of having a fetus with open spina bifida. The use of the nomogram will refine the estimate of risk for a particular woman by combining the estimate derived from the amniotic fluid AFP level with that derived from the maternal serum AFP level. Details are also given for further refining the estimate risk by using information from an amniotic fluid gel acetylcholinesterase determination.