How Soon After Pregnancy Can Perimenopause Start?

How soon after pregnancy can you enter perimenopause? I am 41, and I had a baby about nine months ago. I recently weaned, but my period hasn’t come back. Does this mean I am in perimenopause? How would I know?

—Anonymous

It is possible to go straight from pregnancy to breastfeeding to perimenopause. But it may take some time to know that that is what is going on. However, if this was going to happen to you, I would expect there to have been some signs before your pregnancy that would have tipped you off that you were close to perimenopause, such as changes in cycle length, irregular periods, hot flushes, and night sweats.

A clock in the foreground with a woman opening a sanitary napkin in the background. — doucefleur / Canva

While perimenopause does not necessarily proceed in an orderly fashion from the late-reproductive stage to early perimenopause to late perimenopause, the vast majority of women do spend some time in each stage, though there are a small number of women who go straight from the reproductive years into menopause.

To understand what is going on here, I think it is helpful to quickly review what pregnancy and breastfeeding do to our reproductive hormones. Pregnancy essentially pauses the usual signals that come from the hypothalamus and pituitary gland to direct our ovaries to ovulate and make estrogen and progesterone. During pregnancy, the placenta takes over production of our reproductive hormones.

During breastfeeding, prolactin and oxytocin run the show, and they often effectively suppress ovulation. Estrogen and progesterone levels during breastfeeding are similar to the levels seen in menopause. Many women will experience symptoms associated with menopause, such as vaginal dryness, while breastfeeding.

With weaning, the hypothalamus and pituitary gland are allowed to resume their typical functioning. Depending on where in the perimenopausal transition you hit the pause button by becoming pregnant, you may reenter more or less where you left off. So if you were in the late-reproductive stage when you became pregnant, after weaning you might find yourself back in the late-reproductive stage or in early perimenopause.

However, you might also still be experiencing the effects of breastfeeding. Some women’s endocrine systems are more sensitive to the hormones of breastfeeding. For those women, it may take more time for regular menstrual cycles to resume. Women under age 45 should be evaluated for absent or irregular periods, though. So if you haven’t resumed having regular periods within three months of weaning, you should see your doctor to be evaluated for other causes of absent periods.

Ultimately, it is possible to go straight from pregnancy to perimenopause, but it would not be expected before age 45. So if you don’t resume regular periods within three months of weaning, you should see your doctor for an evaluation.