Which of the following can be included under natural methods of birth control?

a. Rhythm method
b. Coitus interruptus
c. Lactational amenorrhea

The rhythm method is also known as periodic abstinence. It involves abstaining from coitus during day 10 to 17 of the menstrual cycle, as ovulation is most likely to occur in this period and the chances of pregnancy are high.

Coitus interruptus is a method which involves the withdrawal of the penis from the vagina before ejaculation.

Lactational amenorrhea is based on the fact that ovulation does not occur in the period of intense lactation after parturition. Thus, the chances of pregnancy are low in this period.