Cole J B, Beighton F C, Jones I H
Br Med J. 1975 Oct 25;4(5990):217-9. doi: 10.1136/bmj.4.5990.217.
The sexual behaviour and contraceptive practices of a random sample of unmarried university students were compared with those of a group attending the student health service with an unplanned pregnancy. The immediate cause of most pregnancies in this series was incorrect use of a rhythm method. Irregularity of the menstrual cycle may have been a contributing factor in many cases. Psychological factors influencing the desire for pregnancy, while present, were not major contributing causes in many pregnancies.
将一组随机抽取的未婚大学生的性行为和避孕措施与一组因意外怀孕而前往学生健康服务中心就诊的学生进行了比较。在这一系列案例中,大多数怀孕的直接原因是节律避孕法使用不当。月经周期不规律在许多情况下可能是一个促成因素。影响怀孕意愿的心理因素虽然存在,但在许多怀孕案例中并非主要促成原因。