Understanding the Link Between Breastfeeding and Fertility

The choice of which contraceptive method to use after childbirth is an important decision that should be made during the pregnancy in order to avoid unwanted surprises. The return of fertility after childbirth is influenced by many factors and can return faster than we think.

Firstly the return of fertility after childbirth is dependent on whether the mother is breastfeeding or not.

In general, absolute infertility lasts 6 weeks after the birth in an exclusive breastfeeding woman and 3 weeks if there is no breastfeeding.

Why is there a difference?

The answer is based on the hormones that are involved in breastfeeding.

Everything Starts in the Brain

The reproductive hormones are the messengers that send information from the brain to the ovaries and vice versa. The menstrual cycle is controlled by the hypothalamus and pituitary gland which are both situated in the brain. These control centers in the brain are responsible for sending messages to the ovaries to ovulate and secrete the reproductive hormones: estrogen and progesterone. The hormones also act on the uterus, cervix, breasts and other organs.

The Hormonal Cycle

At the beginning of the menstrual cycle, follicle-stimulating hormone (FSH) stimulates the ovaries to mature a few follicles (fluid-filled sacs that contain immature eggs called oocytes) and as they mature they produce a hormone called estrogen. The level of estrogen continues to rise as the follicles grow and mature until the levels get to a certain high level that then stimulate the control center in the brain to release a new hormone called luteinizing hormone (LH) which is better known as the LH surge. The LH surge is what causes ovulation, which is the expulsion of the oocyte from the follicle out of the ovary to be picked up by the fallopian tube. If the oocyte is fertilized it makes its way through the fallopian tube towards the uterus. The follicle that held the oocyte before ovulation becomes the corpus luteum and it releases another very important hormone called progesterone.

What Happens Hormonally After Childbirth?

Immediately after childbirth a new hormone called prolactin stimulates milk production. If a woman is not breastfeeding or if the initial milk is not extracted from the breast, the production of prolactin will slowly cease. If milk will be produced until eventually there is no more prolactin nor milk production and the usual hormonal pattern will return ultimately leading to ovulation. 

If the woman is breastfeeding, each time the nipple is stimulated there is a secretion of prolactin which produces a positive feedback loop which stimulates the production of more milk. The prolactin has an inhibiting factor on the hypothalamus and pituitary gland in the brain which impede all ovarian hormonal activity for an undetermined amount of time. If there is no ovarian activity there cannot be ovulation

It is important to note though that breastfeeding itself does NOT indicate infertility.