The outcome and pathological background of 182 pregnancies with mid-trimester oligohydramnios are discussed. Maternal serum alpha-fetoprotein (AFP) concentration in the 16th week of gestation was also determined in 119 cases. MSAFP in pregnancies with oligohydramnios associated urinary tract malformations was found to be mostly in the normal range, but it is often elevated in the cases without malformation. In addition, normal AFP was found in most cases, where the newborns survived the perinatal period. It can be concluded, that the elevated maternal serum AFP without ultrasonically detectable malformation refers to the extrafetal origin of the oligohydramnios, and it is recommended to take it into consideration in the genetic counselling practice.