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Measurement of alpha1-fetoprotein by rocket immuno-electrophoresis in cord serum from a consecutive series of 422 newborn infants showed a negative correlation with gestational age. The coefficient of correlation was divided by 0.70 for girls and divided by 0.74 for boys. For a given alpha1-fetoprotein concentration in cord blood the confidence limits for prediction of gestational age for both sexes were calculated to +/- 24 days. It is concluded that determination of alpha1-fetoprotein in cord serum is of limited help in the evaluation of maturity.

We studied the precision and accuracy of SF measurements. Five trained obstetricians made three measurements of SF on each of 33 patients in the third trimester. The intraobserver variation varied from 0 cm to 8 cm, and comprised on average 1.5 to 2 cm (95th centiles 2.5 to 4 cm). The interobserver variation varied from 1 to 13 cm, and comprised on average 4 cm (95th centile 8 cm). The accuracy of SF measurements was estimated by comparison with ultrasound-guided measurements, which showed a very high precision. Two of the investigators differed significantly, by -1.56 cm and -1.97 cm, from the other 3.