Control of Reproduction in Mammals 
of such short cycles is less than that observed in normally- 
menstruating women, i.e., 3-2 per cent for 10 mg., 4-9 per cent 
for 5 mg., and 10-4 percent in the non-medicated, normal men- 
strual cycles. 
The volunteers in this project have employed this method of 
ovulation inhibition for purposes of contraception. The record 
from April, 1956 to December, 1961 of conceptions at the 
various dosages we have used is given in Table I*. The concep- 
tion rate is remarkably low, and control at the lowest dosage 
Table I 
FERTILITY IN PATIENTS TAKING ENOVID 
Daily dosage of Enovid 
IO mg. 5 mg. 2°5 mg. 
Number of pregnancies 22 15 2 
Years of medication 789°3 1,579°1 217°S 
Pregnancy rate per 100 woman 2:8 0°95 led. 
years 
employed (2-5 mg./day) is just as effective as at the highest 
dosage (10 mg./day). We have several times pointed out that 
with faithful following of the medication regimen, contraceptive 
efficiency is practically 100 per cent. This is illustrated in 
Table II, which compares the conception rates for women 
Table II 
FERTILITY IN PATIENTS TAKING ENOVID 
Number of Number of Years of Pregnancy rate per 
tablets missed pregnancies medication 100 woman years 
Oo 4 25343°4 0°17 
I-5 16 193°2 8-3 
6-19 20 49°6 40°3 
All cycles 40 2,586-2 I°5 
Controls 124 59°0 210°0 
allegedly taking a pill every day during the 20 days, for those 
missing a few pills and for those missing more than five pills. 
83 
