J.B. Scrimgeour

Maternal serum-alpha-fetoprotein measurements as an early indicator of low birth-weight.

In a prospective trial of 4224 pregnancies, 103 women had serum-alpha-fetoprotein (A.F.P.) above 2-3 times the median value for their stage of gestation. 10-7% of these delivered infants with birth-weights less than 2-5 kg. This was significantly greater than the rate of 4-2% for low-birth-weight infants in the general population. At higher multiples of the median serum-A.F.P. value the proportion of pregnancies leading to low-birth-weight infants was even greater. It is suggested that early identification of pregnancies with high risk of premature delivery may be an important corollary of maternal serum A.F.P. screening.

MATERNAL PLASMA ALPHA‐FETOPROTEIN SCREENING FOR FETAL NEURAL TUBE DEFECTS

Maternal plasma alpha‐fetoprotein (AFP) screening for fetal neural tube defects (NTD) was used as a part of routine antenatal care in three hospitals over a 26 month period. Blood samples were obtained for plasma AFP measurement at 15 to 20 weeks gestation from 6377 women, representing 79 per cent of antenatal bookings. The outcome of pregnancy was ascertained in 96 per cent of patients: 13 cases of anencephaly and 7 of open spina bifida were detected by plasma screening and a further 3 cases of open NTD through the mothers previous medical history and amniotic fluid determination. Four fetuses with open NTDs and four with closed NTDs were not detected by plasma AFP measurement and the detection efficiency for open NTDs was thus 83 per cent. Integration of screening into the existing pattern of antenatal care required only minor alterations in clinic schedules. Some extra time was needed for explanation of the objectives of the study, for ultrasound examination and for amniocentesis. Eight patients declined the offer of a plasma test, while only one refused an amniocentesis.

ANTENATAL DIAGNOSIS AND AMINOACID COMPOSITION OF AMNIOTIC FLUID

Abstract Twenty-seven aminoacids and related compounds have been identified in human amniotic fluid. The concentrations of these various substances have been determined at various stages of pregnancy. The results are presented in the hope that the information may prove useful in the antenatal diagnosis of certain genetic disorders associated with aminoaciduria.

Effect of gestational age on screening for neural-tube defects by maternal plasma-A.F.P. measurement.

Maternal plasma or serum alpha-feto-protein (A.F.P.) concentrations were measured once between 8 and 22 weeks of gestation in each of sixty-two pregnancies which resulted in an infant with a neural-tube defect. Between 13 and 22 weeks of pregnancy twenty-two of the forty-one cases tested (54%) had A.F.P. values greater than three times the median value for unaffected pregnancies (which is equivalent to the 97th percentile of normal), and many of these values were very high indeed. However, before the 13th week of pregnancy only one of the twenty-one cases (5%) had an A.F.P. value more than three times the median for unaffected pregnancies, and this value was not very high. This indicates that in antenatal screening for anencephaly or spina bifida, A.F.P. should be measured in blood taken from the mother during the second trimester.

THE RELATION BETWEEN MATERNAL PLASMA ALPHA‐FETOPROTEIN AND BIRTH WEIGHT IN TWIN PREGNANCIES

In the course of routine screening for neural tube defects, maternal plasma alpha‐fetoprotein (AFP) was measured between 15 and 23 weeks of gestation in 64 twin pregnancies. Women with AFP levels more than twice the median for singleton pregnancies gave birth to infants with significantly decreased birth weights. Women with AFP less than the median also tended to produce twins with decreased birth weights. The distribution of gestations at delivery suggested that in twin pregnancies low AFP values gave an early warning of growth retardation while high values signal possible premature delivery.

Maternal plasma α‐fetoprotein and low birthweight: a prospective study throughout pregnancy

Summary. Maternal plasma α‐fetoprotein (AFP) was measured serially between 15 weeks gestation and term in 520 patients. Thirty‐seven of these women were delivered of normal singleton infants with birthweights <2·5 kg. The median plasma AFP values in this group of women were highest between 15 and 20 weeks gestation and then declined steadily towards term. It is concluded that the use of maternal plasma or serum AFP in the early detection of low birthweight babies is optimal in the period most suitable for screening for fetal neural tube defects.

AMINOACID COMPOSITION OF AMNIOTIC FLUID IN CENTRAL- NERVOUS-SYSTEM MALFORMATIONS

Abstract Quantitative aminoacid analysis of amniotic fluid at various stages of gestation has been carried out in 33 cases of central- nervous-system (C.N.S.) malformations. All the mothers were rhesus-positive and the fetuses were believed to be alive when fluid was obtained. There was a significant increase in the amount of various aminoacids, which was particularly pronounced in the case of certain neutral aminoacids (methionine, isoleucine, leucine, tyrosine, and phenylalanine). If the observed changes in the aminoacid composition of amniotic fluid in C.N.S. malformations should prove to be unrelated to fetal distress, aminoacid analysis might be a useful adjunct in the antenatal diagnosis of such disorders.