Open fetal malformations in incorrectly dated pregnancies with initially low maternal serum alpha-fetoprotein

Improved performance in a prenatal screening programme for Down's syndrome incorporating serum-free hCG subunit analyses

A prenatal screening programme for Down's syndrome potentially detecting 76 per cent of affected pregnancies in the South Australian general population at an amniocentesis rate of 3.9 per cent was designed following analysis of mid-trimester serum samples from 57 women who carried an affected fetus. This equates to one affected pregnancy being detected for 41 chromosomal analyses performed. For the experimental series, 75.4 per cent of affected pregnancies were detected, while 4.1 per cent of control specimens produced estimated risk odds consistent with further action. A maternal risk odds of birth of a Down's syndrome fetus of 1:420 was taken as the decision value, which is the prevalence of Down's syndrome births to 35-year-old mothers in South Australia. This screening performance was achieved by investigating combinations of serum analytes not previously reported and by refining the calculation of maternal risk odds to include selective weighting of indicator analytes. Combination of the measurements of free alpha-subunits and beta-subunits of chorionic gonadotrophin, alpha-fetoprotein, unconjugated oestriol, and placental lactogen was found to be most effective in indicating Down's syndrome fetuses. In all combinations of analytes tested, replacing the measurements of free alpha-subunits and free beta-subunits of chorionic gonadotrophin with the measurement of intact chorionic gonadotropin produced a less effective screen.

Maternal serum alpha-fetoprotein levels in pregnancies among black and white women with fetal open spina bifida: a United States collaborative study

In the present study second-trimester maternal serum alpha-fetoprotein levels were analyzed from 146 pregnancies associated with fetal open spina bifida to identify whether affected pregnancies from the black population were associated with higher maternal serum alpha-fetoprotein levels than their white counterparts. Pregnancies in black women not affected by open spina bifida are already known to have higher maternal serum alpha-fetoprotein levels. All of the cases were analyzed with gestational ages assigned by last menstrual period, and all maternal serum alpha-fetoprotein values were expressed as multiples of the median, to correct for differences in gestational age and assay among the 15 centers reporting data. The levels from affected pregnancies in white and black women fit log Gaussian distributions, with medians of 3.10 and 4.37 multiples of the median, respectively, on the basis of singleton, unaffected, white pregnancy medians. These results support adjustment of maternal serum alpha-fetoprotein values for race in black women; in addition, if a screening program's policy is to screen at a comparable risk in the two races, a higher maternal serum alpha-fetoprotein multiple of the median cutoff would be justified for black women.