Lactational amenorrhea prevents pregnancy due to:

The correct answer is Option (2) → Intense lactation

Lactational amenorrhea means no menstruation during the period of breast-feeding. This method of birth control rests on the fact that ovulation, and therefore the menstrual cycle, does not occur during the period of intense lactation after parturition. As long as the mother feeds the child fully, the chance of conception is almost nil. NCERT says that the method is effective only up to a maximum period of six months following parturition.

(1) Milk production increases LH levels — Incorrect. LH (luteinising hormone) is the pituitary hormone whose surge causes ovulation. If milk production raised LH, it would favour ovulation, not stop it.

(2) Intense lactation — Correct. Ovulation does not occur while the mother breast-feeds fully, so she cannot conceive.

(3) Oxytocin stimulates ovulation — Incorrect. Oxytocin causes the uterus to contract during childbirth and the milk to be ejected during suckling. It does not stimulate ovulation.

(4) Estrogen — Incorrect. Estrogen from the growing follicle prepares the uterus and helps to start the LH surge that leads to ovulation. It is not the reason for the lack of ovulation.

NCERT Extract:
Population Stabilisation and Birth Control – “… Withdrawal or coitus interruptus is another method in which the male partner withdraws his penis from the vagina just before ejaculation so as to avoid insemination. Lactational amenorrhea (absence of menstruation) method is based on the fact that ovulation and therefore the cycle do not occur during the period of intense lactation following parturition.”