A retrospective study was carried out in 47 patients 22 to 43 years of age, with a mean of 32.3 years, with a total of 51 high-risk pregnancies. The patients were treated with Gravibinon starting at the 5th week of pregnancy, and continuing up to the 20th. Indications for treatment were low progesterone or low estradiol levels, or both; these patients made up Group I. Group II patients showed a rapid drop in the progesterone and estradiol values after stimulation therapy despite ongoing pregnancy. The third group comprised women with PCO syndrome, who had previously anovulation or corpus luteum insufficiency. The pregnancy rate was 66.7%. In 9.8% a biochemical pregnancy was diagnosed through the hormone measurements. These biochemical pregnancies were not influenced by Gravibinon treatment. In 3.9% an empty cavity was found. In 11.8% abortion occurred prior to the 16th week of gestations despite Gravibinon treatment. In 7.8% late abortions occurred. In one case pregnancy was terminated owing to chromosomal anomalies. The pregnancy rate in all three groups was nearly equal, with group I at 20%, group II at 21.4%, and group III at 20%. In these high-risk groups it was found that treatment with an estrogen/progestin combination such as Gravibinon appears to be an effective treatment of an endangered pregnancy. An increased risk of specific anomalies was not observed.