The secretor status of the foetus.

One hundred amniotic fluids were tested for the presence of ABH blood group substances. Gestation at amniocentesis ranged from 12 to 28 weeks, with a mean of 16.6 weeks. The secretor status of the fluid was correlated with the secretor status of the baby after birth as determined from a sample of saliva. Fluid and saliva correlated in 98% of cases. It is felt that contamination with blood is likely to be the main source of error in typing amniotic fluids. However, because of the weaker activity of the anti-H serum, the detection of the presence or absence of H-substance can be doubtful if duplicate tests are not carried out. It is recommended that all fluids be checked for contamination with blood and that duplicate assays be done on two successive occasions. If these precautions are taken, the secretor typing of the amniotic fluid accurately reflects the secretor status of the individual foetus. Though probably not of wide application, the test could be of value in prenatal detection of dystrophia myotonica in individual cases.