Postpartum Night Sweats: How Long They Last, Breastfeeding, and Warning Signs

Waking up with a soaked shirt and damp sheets is one of the less talked-about parts of the first weeks with a baby. Research on it is surprisingly thin: the figures repeated online often trace back to one study. This guide looks at what that study did and didn’t find, whether breastfeeding really changes things, and how to tell ordinary sweats from a reason to call.

It’s worth separating terms first. The NHS says it’s normal to sweat at night if the room or bedding is too hot, and that true night sweats mean your nightclothes and bedding are soaking wet even though where you’re sleeping is cool.

How common are they? The numbers, checked

The main source is a study led from the University of Pittsburgh, published in 2013. Researchers followed 429 women through pregnancy and the year after birth, asking at each visit whether they’d had hot flashes that disturbed their sleep. Across all visits after delivery, 29% reported them at least once.

Time after birth	All women in the study	Women with no history of depression or bipolar disorder
2 weeks	20%	11.5%
12 weeks	14%	9.3%
26 weeks	11%	4.7%
52 weeks	10%	3.8%

A figure worth correcting. You’ll often see that “35%” of new mothers get night sweats, including on Cleveland Clinic’s page, which lists this study among its references. In the paper itself, 35% is the figure for women reporting hot flashes during pregnancy. The postpartum figure is 29%.

What this study doesn’t tell you. Three limits matter:

• Who was studied. Most of the women had a history of major depression or bipolar disorder, since the parent studies were about those conditions. That’s why we added the second column. In that smaller comparison group, rates were lower at every visit. The authors call for a population-based study, and we found none.
• What was asked. The question was about sleep-disturbing hot flashes over the past two weeks. It didn’t measure sweating, so it may undercount women who sweat without waking and may not capture sweats exactly as you experience them.
• Who stayed in. There were 291 women at week 2 and 201 at week 52, so the later numbers rest on a smaller group.

Why it happens

Hormones. During pregnancy, estrogen rises about 8-fold and progesterone 9-fold, according to a 2016 review, and both fall rapidly once the placenta is delivered. Cleveland Clinic says low estrogen makes the hypothalamus, your body’s thermostat, believe you’re too hot, for reasons researchers don’t completely understand.

A useful clue comes from outside the postpartum period. In a 2016 experiment by Harvard Medical School researchers in Boston, 29 healthy premenopausal volunteers (mean age 27.3) had their estradiol suppressed with a drug, and 69% developed hot flashes. This shows estrogen withdrawal alone can cause hot flashes in young women. It doesn’t prove the same process explains sweats after birth, and the Pittsburgh authors note that not every woman with these hormone changes gets them, so other systems are likely involved. We found no study measuring hormone levels against postpartum night sweats directly.

Fluid. StatPearls’ postpartum physiology chapter describes a period of brisk diuresis, particularly in the first 1 to 2 weeks, as the body clears fluid held during pregnancy. It describes this as increased urine output. Cleveland Clinic says night sweats “could happen” because your body is shedding extra fluid. That timing fits the week-2 peak, but we found no study measuring sweat as a route, so this remains a reasonable idea rather than a finding.

The first day. StatPearls also notes that sweating, shivering or chills can accompany a slight temperature rise in the first 24 hours after delivery, which usually settles within the first day.

Does breastfeeding make them last longer? Tracing the claim

Cleveland Clinic says you may have night sweats longer if you’re breastfeeding, because prolactin keeps estrogen low. The biology has real support: StatPearls describes prolactin suppressing the signals to the ovaries, and a low-estrogen state in lactating women. But does that translate into more sweats? The Pittsburgh study recorded breastfeeding at every postpartum visit, so we pulled the numbers from its Table 2.

Time after birth	Breastfeeding (50% or more of feeds): hot flashes	Not breastfeeding (under 50% of feeds): hot flashes
2 weeks	37 of 165 (22.4%)	20 of 121 (16.5%)
12 weeks	12 of 114 (10.5%)	21 of 122 (17.2%)
26 weeks	6 of 92 (6.5%)	19 of 125 (15.2%)
52 weeks	1 of 16 (6.3%)	20 of 184 (10.9%)

Our read: breastfeeding mothers reported slightly more at week 2 and fewer at each later visit, the reverse of what the claim predicts. The paper does not mark breastfeeding as significantly associated with hot flashes.

Please don’t over-read this in the other direction. The numbers are unadjusted, and breastfeeding mothers in this sample may have differed in education, smoking or mood, each of which related to hot flashes. Only 16 women were still at 50% or more of feeds at week 52, and “breastfeeding” included mixed feeding. What’s fair to say is this: lower estrogen in lactation is a plausible reason sweats could last longer, but the available data don’t show that they do. We found no evidence that weaning would stop night sweats, so we don’t see it as a reason on its own to stop.

How long will they last? Where the sources disagree

Source	What it says	When to check
Cleveland Clinic	Worst in the first two weeks, typically end after a few weeks	Sweats lasting longer than three weeks
Pittsburgh study	Peak at week 2, then decline; some still report them at a year	Doesn’t give advice
NHS	General adult guidance, not postpartum-specific	Regular sweats that wake you or worry you
American Family Physician, 2020	Most people with persistent night sweats in primary care have no serious underlying disorder	Persistent sweats deserve a history and exam

These fit together better than they first appear. “A few weeks” describes the typical drop, while the study shows a meaningful minority still reporting hot flashes at 12 weeks and beyond. So if you’re at week 5 and otherwise well, that isn’t unusual, but it’s still reasonable to mention at a visit, because the check is simple.

When to call: a decision guide

What you notice	What to do
Sweats in the first few weeks, feel well, no fever	Expected. Try the steps below
Lasting more than about three weeks	Call your provider, as Cleveland Clinic advises. Usually not urgent
Temperature of 100.4°F (38°C) or higher	Seek care immediately. The CDC lists this as an urgent maternal warning sign up to a year after delivery. See also breastfeeding while sick
Sweats with chills or pain	Call promptly. Cleveland Clinic says this could mean infection
A hot, sore, red area on the breast with flu-like feelings	Call. See our mastitis guide
Foul-smelling discharge, soaking a pad an hour, or clots bigger than an egg	Seek care immediately (CDC)
Chest pain, trouble breathing, fainting	Seek care immediately, and call 911 if severe. The CDC lists these as urgent signs
Racing heart, anxiety, insomnia, weight loss at 1 to 4 months	Ask for thyroid testing
Cough, diarrhea or unexplained weight loss	See your doctor, as the NHS advises

Thyroid. The American Thyroid Association says postpartum thyroiditis affects about 5% to 10% of US women, and its overactive phase typically comes 1 to 4 months after birth and is often overlooked because symptoms get blamed on life with a new baby. American Family Physician lists hyperthyroidism among conditions commonly linked with night sweats. By our reading, this makes sweats that return or worsen after they’d been easing a good reason to ask for a TSH test, particularly with palpitations. Our postpartum thyroiditis guide explains the phases, and the same window also brings postpartum hair loss, so don’t assume either symptom explains the other.

Mood. Depressive symptoms were the factor that stayed linked to hot flashes after birth in the Pittsburgh study’s adjusted model (odds ratio 1.19 per point on a depression rating scale). In the Harvard experiment, depressive symptoms tracked with disturbed sleep and nighttime hot flashes. These studies can’t say which comes first, and sweats alone don’t mean you are depressed. Still, if your nights are wrecked and your mood is low, tell your provider, because it deserves attention in its own right. You can reach the National Maternal Mental Health Hotline 24/7 at 1-833-TLC-MAMA. If you have thoughts of harming yourself or your baby, call or text 988 or call 911.

Medicines and other causes. The NHS lists some antidepressants, steroids and painkillers, along with alcohol or drug use, anxiety and low blood sugar. Oddly, the Pittsburgh authors note that SSRIs are used to reduce hot flashes, so antidepressants can cut either way. Don’t stop a medicine on your own. Ask whoever prescribed it.

If you need more tests, American Family Physician describes a stepwise workup that can include a blood count, TSH, tuberculosis and HIV testing, C-reactive protein and a chest X-ray.

What helps at home

We found no trial of any treatment for postpartum night sweats, so all of this is practical advice rather than tested therapy. Cleveland Clinic suggests:

• Light cotton or silk pajamas and cotton sheets
• A bath towel under you and a second pillowcase
• A waterproof mattress protector
• A fan, an open window or lower air conditioning
• Plenty of water, since heavy sweating can dehydrate you

Our own additions, for practical reasons: keep a dry top and towel within reach, so a middle-of-the-night change doesn’t fully wake you, and do it around a feed if you can. Since broken sleep is already wearing you down, any step that shortens the change is worthwhile.

One safety note: towels and extra pillows stay with you, not near your baby. The AAP says to keep blankets and pillows out of your baby’s sleep space, and to place your baby on their back on a firm, flat surface such as a crib or bassinet.

Medicines for menopausal hot flashes weren’t tested in these studies, so please don’t borrow one. Ask your provider, and check our nutrition and health hub for more on looking after yourself while nursing.