[Proposed normal values for alpha fetoprotein in maternal serum for the detection of neural tube closure defects and Down syndrome. Preliminary study].

To establish a normal range of alpha fetoprotein in maternal serum (AFP sm) in the population at the "20 de Noviembre" Hospital in Mexico City, there were studied 46 patients with a normal pregnancy confirmed with ultrasonography between 16 to 18 week of gestation. The 97 determinations of AFPsm were made by radioimmunoanalysis. The multiples of the median (MoM) were 2.16 al 16th weeks, 2.33 a 17th week 2.43 al 18th week of pregnancy. Now the methods to determine abnormalities in the product and the genetics studies are proposed only to the patients considered high risk (older than 35 years old, previous malformed son or family history of those abnormalities). AFPsm and the establishment of normal range allow us to amplify the study to every pregnant woman and to determine those malformations in the pregnant women of low risk which represents about 90-95% of DCTN and about 80% of SD.