910 RADIATION BIOLOGY 



irradiated between conception and the third month, 31 per cent between 

 the third and fifth months, and 11 per cent after the fifth month. In 

 Goldstein and Murphy's compilation (1929), 79 per cent of the abnormals 

 come from pregnancies irradiated before the fifth month. 



Russell and Russell (1952) have suggested that, since during at least 

 the early part of the period of major organogenesis, many women are not 

 yet aware that they are pregnant, pelvic irradiation of women of child- 

 bearing age should whenever possible be restricted to the two weeks 

 following a menstruation as there is little chance of an unsuspected preg- 

 nancy during that time. This type of timing should be feasible for 

 diagnostic irradiation (see following paragraph for discussion of dose), if 

 not always for therapeutic. The dangers of irradiation after the period of 

 major organogenesis, which, predicting from the animal results, consist 

 of the production of possibly delayed and less obvious but, from a 

 human point, at least as undesirable effects (e.g., changes in mental 

 abilities, sterility), occur at a time when there need no longer be any 

 doubt of pregnancy. They are, therefore, already avoided in good cur- 

 rent practice. 



It was mentioned earlier (see p. 907) that in experimental work a dose 

 as low as 25 r, the lowest used, may be shown to have an effect on prenatal 

 development (Russell and Russell, 1950b), and there is no evidence that 

 lower doses would not also cause damage detectable in man where even 

 subtle defects are likely to be recognized. This is of significance in 

 medical diagnostic practice since Sonnenblick et at. (1951) found that 

 about one-fifth of sixty-three fluoroscope machines tested emitted^ more 

 than 30 r per minute, and Bell's results (1943) indicate that the length of 

 exposure for a standard gastrointestinal series is 4^2 to 12 minutes, during 

 which time about 50 r may be received at a depth of 10 cm for a panel 

 dose of 30 r/minute. On the other hand, doses received by the uterus 

 in radiographs are comparatively negligible (Mobius, 1951). 



The question of feasibility of radiation-induced therapeutic abortion 

 arose very soon after the beginning of radiological practice. As early as 

 1911, von Klot discusses its pros and cons at considerable length. Dries- 

 sen (1924) cites seven references which claim success and seven others 

 which state X rays to be unsuitable for the induction of abortion in man. 

 Murphy (1929) showed that the abortion rate following postconceptional 

 irradiation was probably no higher than in the population at large. In 

 his review, Schall (1933) states that radiation abortion has finally been 

 discontinued in medical practice because of inconstancy of results; but, 

 three years later, Mayer, Harris, and Wimpfheimer (1936) recommend 

 the method and claim a very high percentage of success. The statement 

 has occasionally been made (Robinson, 1927, and others) that doses high 

 enough to cause maldevelopment usually also terminate pregnancy and 

 thus do not present an appreciable hazard. Whether the unreliability 



