At laparotomy of a woman not suspected and therefore not examined for pregnancy, a gynecologist may stand before an open abdomen exhibiting an enlarged uterus, and be doubtful whether it is a question of pregnancy or not. The difficulty in this situation is most often to decide whether a myoma (or sarcoma) or a pregnancy or possibly both are responsible for the enlargement of the uterus.If i t is considered unsuitable to close the abdomen and run the risk of being obliged to perform relaparotomy, after a more thorough examination (e.g. biologic test of pregnancy, roentgen examination, etc.) the following precautionary measures may be taken: 1) by examining the ovaries, possibly with incision, an attempt should be made to find out whether either of them contains a corpus luteum graviditatis (de ROUVILLE 1928). In practice, however, i t is extremely difficult to distinguish between a gestational and a menstrual corpus luteum.2) by puncture or incision of the uterus the presence or absence of pregnancy may be established. Both methods have their limitations and involve certain risks. Incision of the uterus, if not sufficiently long and deep, might lead to a wrong-diagnosis and the consequential removing of a uterus containing a fetus (HELLSTEN