Prior t o the development of fertility drugs, the natural biological incidence of multiple gestations approximated the formula 1 : N(X-l) where N is 89 and X is the number of fetuses in that gestation. Twins, therefore, would be expected 1 :89 pregnancies. Sextuplets would be expected with a frequency of 1:8g5, or 1:558,405,936 times. Even in an extremely active ultrasound laboratory, where one obstetrical patient is studied every twenty minutes, or approximately 24 per day, it would still take 89,489+ years to find such a patient occurring randomly. Clomid", a fertility drug, increases the incidence of twinning from 1:89 to 1 : l O ( I ) . With Perganol**, another fertility agent, there is even a greater chance of multiple gestations being produced (2, 3).
In the case presented here, ERS, Colorado General Hospital No. 487-30-8, the patient had received Perganol because of infertility. Her last menstrual period was 2/12/73, and the first ultrasonic examination was at 18 weeks' gestation. The ultrasonic examination was requested because the uterine size was greater than expected for the gestational age. Initial reading of the ultrasound films suggested four definite fetuses with a question of a fifth. The difficulty in interpretation lay in the fact that there was poor correlation between the number of heads and chests. On re-reading, a sixth fetus seemed *Clomiphene Citrate (CIomidB ) -Wm. S. Merrell C o : Div.