Diagnosis of intrauterine fetal growth retardation by DHAS half-life.

A DHAS test (50 mg i.v.) was performed on 49 women with clinically suspected intrauterine fetal growth retardation (IUGR) in the last trimester of pregnancy. A correlation could be established between the serum DHAS halflife (DHAS-T 1/2) of the mother after DHAS loading and the birthweight percentile of the newborns, which were retrospectively divided into two groups; one with regular intrauterine fetal growth (birthweight greater than 10th percentile) (n = 28) and one with poor intrauterine fetal growth (IUGR) (less than 10th percentile) (n = 21). The DHAS loading test was retrospectively evaluated by the correct diagnosis of intrauterine fetal growth; a DHAS halflife below 4.7 h was taken as a threshold for normal intrauterine fetal growth as indicated by a previous study by our group: DHAS-T 1/2 (less than 10th birthweight percentile): 6.00 +/- 1.43 h (mean +/- S.D.) (n = 18), DHAS-T 1/2 (greater than 10th birthweight percentile): 4.37 +/- 1.06 h (mean +/- S.D.) (n = 28). In 89% (16/18) of the cases (less than 10th birthweight percentile), a prolonged DHAS-T 1/2 (greater than 4.7 h) led to the correct diagnosis of an IUGR. In 75% (21/28) of the cases with regular fetal growth, a DHAS-T 1/2 of less than 4.7 h could be registered. In three cases with intrauterine death of the fetus, a prolonged DHAS-T 1/2 of 7.64 +/- 0.37 h (mean +/- S.D.) was found. Furthermore, IUGR could not be detected in three cases by DHAS loading (DHAS-T 1/2 3.77 +/- 0.51 h (mean +/- S.D.) due to betamethasone induction of lung maturation prior to the DHAS test. Indications for the DHAS test include the diagnosis of an ultrasonographically symmetric IUGR (biparietal and thoracic diameters) in cases with an indefinite gestational age and the detection of a placental sulfatase deficiency by means of a delayed conversion of DHAS to dehydroepiandrosterone.