Pregnancy diagnosis.

Choriionic gonadotrophin is produced by trophoblastic tissue. In pregnancy raised serum levels are associated with increased urinary excretion. The excretion of human chorionic gonadotrophin (HCG) is significantly raised within one week of the first missed period, reaches a peak by the tenth week, and falls thereafter to the twentieth week (Fig. 1). In the second half of pregnancy levels fluctuate but remain ra'ised until after delivery. Biological and immunological tests depend on the detection of increased quantities of chorionic gonadotrophins, and reliable positive results may be expected within four weeks of conception. Positive results are also obtained if there are high levels of luteinizing hormone in the urine. This is particularly likely to