Abstract:
Until recently congenital malformations were studied mainly as anatomical and pathological curiosities. Congenital malformations are now more important because incidence of neutral tube defects might be lowered in the general population. Several complications and malformations of pregnancy have been reported to occur more frequently in cases of fetal neural tube defects (Elwood and Elwood, 1980)
The existence of specific and distinct alpha 1 (0C 1) globulin in human fetus was first noted in 1956 by Berystrand and Czar and named Alpha Fetoprotein (AFP) (Cited by Elwood and Elwood, 1980). It is the protein in the circulation of early fetus being synthesized in the yolk sac, liver and very small amounts originate in the gastrointestinal tract. In the 2nd trimester (13th week) it is 3-4 mg/ml and reaches a maximum at 20th week and continue at this rate until 36th week of gestation. AFP is a single polypeptide change with a molecular weight 64,000. It is temperature stable between -20oC and +36oC and contains Hexose, Hexosamine, Sialic acid, nitrogen and Sulphur.
Maternal serum level of AFP is found to rise progressively at about 12 weeks of gestation and virtually reach base line levels one week after delivery (Elwood and Elwood, 1980). Also, if the concentration of AFP in amniotic fluid is sufficiently high, spill over effect will occur producing abnormally elevated levels in maternal serum, to help in the assessment of the prognostic significance in both complicated and uncomplicated fetal neural tube defects (Gosh at al., 1982). A sharp rise has been reported in maternal serum with placenta previa, molar pregnancy, triploid fetus and ectopic pregnancy due to break down in the fetal maternal barrier (Cederqvist at al., 1983) and in the absence of neutral tube defects there are many non-including under estimated gestational age, twin gestation impending fetal death and rare fetal malformation (Perkes at al., 1982).
Measuring maternal serum AFP levels in the 2nd trimester is an affective screening test. There are not many recent studies in relation to congenial and the hazards associated with amniocentesis and X-rays. Smithell, Chin and Franklins (1964) have reported 3.4% of 180 mothers of Anencephaly had a threatened abortion and 5.7% had Antepartum Hemorrhage. (Cited by Elwood and Elwood, 1980). Amniotic fluid AFP levels are raised in fetuses with neural tube defects which have been spontaneously aborted from the seventh weeks of gestation (Seller at al., 1974).
This relationship, therefore, between the higher maternal serum AFP concentration and different intrauterine conditions of fetus male AFP estimation the most suitable comprehensive test for screening congenital malformations. If the AFP level is very high termination may be carried out (Seller at al., 1973). High risk pregnancies such as antenatal diagnosis with AFP and other related clinical tests, i.e., Amniocentesis, Sonography may offer a combined platform for induction of therapeutic abortion (after considering the technical, ethical and legal implications) for the future benefit both for the mother and the child.
