Yes, you can breastfeed with PMOS (PCOS), and many women do. The condition, now renamed polyendocrine metabolic ovarian syndrome but still widely known as polycystic ovary syndrome, does not stop you making milk. What the research does show is that some women with PMOS (PCOS) are more likely to struggle with low milk supply, and the strongest suspects are insulin resistance, higher androgen levels, less breast growth during pregnancy and a higher body weight. The good news: knowing this before your baby arrives means you can get support early, which is exactly when it makes the biggest difference.

This guide covers what the studies actually found, the early signs that feeding is not going to plan, seven practical ways to protect your supply, what to know about metformin and herbal "milk boosters", when your periods may come back, and how to look after your own mental health along the way. No guilt, no scare stories. Just the information nobody handed you at your booking appointment.

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In this article

• Can you breastfeed with PMOS (PCOS)?
• Does PMOS (PCOS) affect milk supply?
• Why might PMOS (PCOS) affect milk production?
• How do you know if your baby is getting enough milk?
• How can you protect your milk supply with PMOS (PCOS)?
• Is metformin safe while breastfeeding, and does it boost milk?
• Do herbal milk boosters or supplements help?
• When will your periods come back after birth?
• Does breastfeeding help your long-term health?
• How do you look after your mental health while feeding?
• FAQ

Can you breastfeed with PMOS (PCOS)?

Yes. PMOS (PCOS) does not stop you breastfeeding, and in large population studies most women with the condition breastfeed at similar rates to everyone else.

Let's start there, because a lot of what you will read online makes it sound like PMOS (PCOS) and breastfeeding are a doomed combination. They are not. In one of the largest studies on this question, researchers followed 5,605 Australian women across 12,920 pregnancies, including 601 pregnancies in women who reported PCOS. Once they accounted for other factors, PCOS on its own was not significantly linked to whether women started breastfeeding or how long they kept going (Rassie et al., 2024) ^[1].

So why does the worry exist? Because "most women are fine" is not the same as "every woman is fine". Smaller, more detailed studies suggest there is a subgroup of women with PMOS (PCOS), often those with more pronounced metabolic features, who are more likely to find milk supply hard work. If that turns out to be you, you're not imagining it, and it is not a reflection of how hard you are trying.

If you are newer to the name change, our guide to what the switch from PCOS to PMOS means for you explains why "metabolic" is now right there in the title. It matters here, because metabolism turns out to be a big part of the breastfeeding story.

Does PMOS (PCOS) affect milk supply?

It can, for some women. The research points to metabolic factors (insulin resistance and higher body weight) and less breast growth in pregnancy, rather than the diagnosis itself.

The research on this is smaller than it should be, but it does tell a fairly consistent story. Here is what the key studies found:

Study	Who was studied	What it found
Rassie et al., 2024 [1]	12,920 pregnancies in 5,605 Australian women (601 with PCOS)	PCOS alone was not significantly linked to breastfeeding outcomes. Obesity was: 2.1 times the odds of not starting breastfeeding and 1.8 times the odds of stopping before 6 months.
Vanky et al., 2012 [2]	186 Norwegian mothers with PCOS, followed up after a metformin trial	Women whose bra size did not increase in pregnancy breastfed for less time (7.3 vs 9.3 months of any breastfeeding) and had higher BMI and fasting insulin.
Nommsen-Rivers et al., 2019 [3]	46 mothers with low milk supply (not only PCOS)	Mothers with signs of insulin resistance were producing less milk at the start of the study than those without.

Put together, the picture looks like this: the label PMOS (PCOS) is not the problem. The metabolic and hormonal features that often come with it are. That is a much more useful way to think about it, because those features are things you can talk to your GP about, and some of them you can support.

One honest note on weight: the link between higher BMI and shorter breastfeeding is about biology and support, not willpower or blame. It is also not a reason to diet hard in the weeks after birth. More on that below.

Why might PMOS (PCOS) affect milk production?

Three suspects keep coming up: insulin resistance, higher androgen levels and less development of milk-making breast tissue during pregnancy. They often overlap.

Hormonal literacy isn't complicated, it's just rarely taught. So here is the short version of how milk gets made, and where PMOS (PCOS) can get in the way.

1. Insulin resistance

Insulin is not just a blood sugar hormone. The milk-making cells in the breast rely on it too, and a 2017 review argued that insulin resistance "may be the missing link" between PCOS and low milk supply (Kirigin Biloš et al., 2017) ^[4]. The same review notes that around 30 to 40% of women with PCOS have impaired glucose tolerance. That lines up with the finding that mothers with signs of insulin resistance started out producing less milk ^[3]. If insulin resistance is new territory, our guide to PMOS (PCOS) and insulin resistance walks through the signs and tests.

2. Androgens

Higher levels of androgens (the so-called "male" hormones, which every woman has) are one of the defining features of PMOS (PCOS). An earlier Norwegian study, as summarised in the 2017 review, found that higher levels of one androgen (DHEAS) late in pregnancy were linked with less breastfeeding at one and three months ^[4]. The later follow-up study, though, concluded that androgens had no impact on breastfeeding ^[2]. So this one is still unsettled.

3. Breast development in pregnancy

During pregnancy, breast tissue grows to build the "factory" that makes milk. In the Norwegian follow-up study, women with PCOS whose bra size did not go up during pregnancy breastfed exclusively for 3.4 months on average, compared with 4.7 months for those whose breasts did grow ^[2]. Bra size is a rough, self-reported measure, but it is a simple thing to notice and mention to your midwife.

This is what I wish someone had told me: none of these mean you will have low supply. They are reasons to have a plan and a support person lined up before your baby arrives, rather than discovering the problem at 3am on day four.

How do you know if your baby is getting enough milk?

Watch nappies, not the clock. From day 5, the NHS says to expect at least 6 heavy wet nappies and at least 2 soft yellow poos a day, with steady weight gain.

You cannot see how much milk is going in, which is maddening. The NHS gives these signs that feeding is going well ^[5]:

Sign	What to expect
Wet nappies (first 48 hours)	Usually 2 or 3
Wet nappies (from day 5)	At least 6 heavy, wet nappies every 24 hours
Poos (from day 4, first few weeks)	At least 2 soft, yellow poos a day, about the size of a £2 coin
Weight	Some weight loss in the first 3 to 4 days is normal, then steady gain

If these signs are not there, or your gut tells you something is off, the NHS is clear: ask for help early, from your midwife, health visitor or a breastfeeding specialist ^[5]. You do not need to wait until things are "bad enough". Your body is trying to tell you something, and so is your baby's nappy.

How can you protect your milk supply with PMOS (PCOS)?

Plan ahead, feed early and often, get a feed watched by a specialist, express after feeds once established, and look after your blood sugar and sleep where you can.

Here are seven steps, based on NHS breastfeeding guidance and what the PMOS (PCOS) research suggests.

1. Tell your midwife about your PMOS (PCOS) before birth. It is not on every checklist. Ask for your feeding to be flagged so someone checks in during the first week.
2. Line up support in advance. Find your local breastfeeding group or infant feeding team now, and save the National Breastfeeding Helpline number: 0300 100 0212 ^[6].
3. Feed early, often and on demand. The NHS advises feeding as often and for as long as your baby wants, and offering both breasts ^[5]. Milk supply works on demand, so more removal tends to mean more production.
4. Get a feed watched. Positioning and attachment problems are common for everyone, and they can look exactly like low supply. A midwife, health visitor or breastfeeding specialist can spot this in minutes ^[5].
5. Express after feeds once feeding is established. The NHS suggests this as a way to boost supply ^[5]. Ask your feeding specialist when and how often is right for you.
6. Eat regularly and keep your blood sugar steady. This is not the moment for strict dieting. Regular meals built around protein, fibre and slow-release carbs are kinder to insulin sensitivity than skipping meals then grazing on biscuits at midnight (we have all been there). Our guide on PMOS (PCOS) and weight gain explains why crash dieting tends to backfire.
7. Ask about your metabolic health. If you had gestational diabetes, or you have signs of insulin resistance, ask your GP whether your postnatal checks should include a blood sugar test. It is relevant to your long-term health and, possibly, to your milk.

And if you do all of this and your supply is still low? Combination feeding (breast milk plus formula) still counts. Any breast milk counts. A fed baby and a mother who is not falling apart counts most of all.

Is metformin safe while breastfeeding, and does it boost milk?

The NHS says you can usually take metformin while breastfeeding, as only tiny amounts pass into milk. But the evidence that it increases supply is weak.

Metformin is commonly prescribed for PMOS (PCOS), and the NHS itself now describes it as used for symptoms of PMOS. On breastfeeding, the NHS says you can usually take it because it passes into breast milk only in tiny amounts, and side effects in breastfed babies are rare. Check with your doctor first ^[7].

Because insulin resistance seems to play a part in low supply, you will see metformin talked about online as a "milk booster". The research does not back that up yet:

• In the Norwegian trial, women with PCOS who took metformin through pregnancy breastfed for about the same length of time as those on placebo (8.8 vs 8.5 months of any breastfeeding) ^[2].
• In a small US pilot trial of mothers with low supply and signs of insulin resistance, 15 women were randomised. The change in milk output was not statistically significant, 44% on metformin had nausea or vomiting, and none felt it was worth continuing (Nommsen-Rivers et al., 2019) ^[3].

Bottom line: if you already take metformin and want to breastfeed, talk to your GP about continuing. Do not start or change it hoping for more milk without medical advice. Bigger trials are needed.

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Do herbal milk boosters or supplements help?

The evidence for herbal "milk boosters" is thin. The one supplement the NHS advises for breastfeeding mothers is 10 micrograms of vitamin D daily in autumn and winter.

Search "increase milk supply" and you will drown in teas, cookies and capsules. Most herbal galactagogues (the technical name for milk boosters) have little good-quality research behind them, and "natural" does not mean "tested in breastfeeding mothers".

Here is what the NHS does recommend ^[6]:

• Vitamin D: everyone, including breastfeeding women, should consider a daily 10 microgram supplement during autumn and winter.
• Vitamin B12: may be advised if you are vegan or have a restricted diet.
• Caffeine: no more than 200mg a day while breastfeeding (roughly two mugs of coffee).
• Free vitamins: you may be eligible through the Healthy Start scheme.

Before you take any supplement while breastfeeding

Speak to your GP, health visitor or pharmacist before starting any supplement, herbal product or botanical tea while breastfeeding, especially if you take prescribed medication such as metformin or you are managing a diagnosed condition. Some herbs that are fine at other life stages have not been studied in breastfeeding at all. If you are planning another pregnancy later, our guide to folate vs folic acid is a good place to start that conversation.

When will your periods come back after birth with PMOS (PCOS)?

It varies. Exclusive breastfeeding often delays periods, but with PMOS (PCOS) your cycle may return irregularly, so don't rely on periods to tell you when you are fertile again.

Frequent breastfeeding suppresses ovulation for many women. The NHS describes the lactational amenorrhoea method (LAM) as a form of contraception that only works if all of these are true ^[8]:

• Your baby is under 6 months old
• You are fully breastfeeding, at least every 4 hours in the day and every 6 hours at night, with no formula or solid food
• Your periods have not returned

Used correctly, the NHS puts LAM at more than 99% effective, falling to about 98% with typical use ^[8].

The PMOS (PCOS) twist: irregular cycles were often your normal before pregnancy, so the "wait for a period" signal is even less reliable. You can ovulate before your first period, and your cycle may come back long, short or not at all for a while. If you do not want to get pregnant again yet, sort out contraception with your GP or sexual health clinic rather than waiting to see. For more on what irregular cycles mean, see irregular periods and PMOS (PCOS).

Does breastfeeding help your long-term health with PMOS (PCOS)?

Possibly. In women who had gestational diabetes, longer and more intensive breastfeeding was linked with a lower risk of type 2 diabetes two years later.

Women with PMOS (PCOS) have a higher risk of type 2 diabetes (we break down what that risk really looks like in PMOS (PCOS) and diabetes). That makes one US study especially interesting.

Researchers followed 959 women who had gestational diabetes for two years after birth. Overall, 11.8% developed type 2 diabetes. Women who breastfed for more than 10 months had less than half the risk of those who breastfed for 2 months or less (adjusted hazard ratio 0.43), and exclusive breastfeeding was linked with a lower risk than formula feeding (Gunderson et al., 2015) ^[9].

Two big caveats. This study was in women with gestational diabetes, not PMOS (PCOS) specifically. And it shows an association, not proof that breastfeeding caused the lower risk. It is a reason to see breastfeeding as one helpful thing among many, not a test you pass or fail. If breastfeeding does not work out for you, there are plenty of other ways to support your metabolic health over the long run.

How do you look after your mental health while breastfeeding with PMOS (PCOS)?

Women with PMOS (PCOS) report more anxiety and depression around pregnancy, so build in support early and tell your midwife or GP how you are actually feeling.

In an Australian study of 5,239 women, those with PCOS reported more perinatal mental health problems. Postnatal depression and/or anxiety was reported by 31.4% of women with PCOS compared with 22.4% without. After adjusting for other factors, the link remained significant during pregnancy but not after birth (Tay et al., 2019) ^[10]. The authors called for women with PCOS to be screened for perinatal mental health problems.

Feeding struggles and low mood can feed each other. If breastfeeding is making you dread every feed, that is important information, not a failure. Tell your health visitor, midwife or GP. Your mental health is part of your baby's care plan too. Our guide to hormonal anxiety covers more of the why and what helps.

Your diagnosis is a starting point, not a verdict. That applies to feeding as much as anything else.

Frequently asked questions

Can PMOS (PCOS) cause low milk supply?

It can for some women. Large studies show most women with PMOS (PCOS) breastfeed at similar rates to other women, but the metabolic features that often come with it, especially insulin resistance and higher body weight, are linked with lower supply and shorter breastfeeding ^[1][2][3].

Can I take metformin while breastfeeding?

The NHS says you can usually take metformin while breastfeeding, because only tiny amounts pass into breast milk. Check with your doctor first ^[7]. There is not good evidence that it increases milk supply.

Does breastfeeding make PMOS (PCOS) worse?

There is no good evidence that breastfeeding worsens PMOS (PCOS). Breastfeeding often delays the return of periods, and in women who had gestational diabetes, longer breastfeeding has been linked with a lower risk of type 2 diabetes ^[9].

Can I get pregnant while breastfeeding if I have PMOS (PCOS)?

Yes. You can ovulate before your first period returns, and irregular cycles make the timing harder to predict. Breastfeeding only works as contraception under strict conditions in the first 6 months ^[8], so speak to your GP or sexual health clinic if you want to avoid another pregnancy.

Is it safe to take supplements while breastfeeding with PMOS (PCOS)?

The NHS advises 10 micrograms of vitamin D daily in autumn and winter for breastfeeding women ^[6]. For any other supplement, herbal product or botanical tea, check with your GP, health visitor or pharmacist first, particularly if you take medication.

Who should I contact if breastfeeding is not going well?

Your midwife, health visitor or a breastfeeding specialist, as early as possible ^[5]. You can also call the National Breastfeeding Helpline on 0300 100 0212 ^[6].

Conclusion

PMOS (PCOS) does not stop you breastfeeding. For most women, the diagnosis alone makes little difference. For some, insulin resistance, androgens and less breast growth in pregnancy can make milk supply harder work. The best thing you can do is plan before your baby arrives: tell your midwife, line up specialist support, learn the nappy signs, and ask for help early rather than late. Feed in the way that works for you and your baby, and look after yourself while you do it. That is not a compromise. That is the plan.

Further reading

• Myo-Inositol in Pregnancy With PMOS (PCOS): The Evidence
• PMOS (PCOS) and Insulin Resistance: Understanding the Link
• PMOS (PCOS) and Diabetes: What Your Risk Really Looks Like
• Anovulation: What It Is, Why It Happens and What Helps

References

1. Rassie K, Dhungana RR, Mousa A, Teede H, Joham AE. Maternal metabolic conditions as predictors of breastfeeding outcomes: insights from an Australian cohort study. Acta Obstet Gynecol Scand 103(8):1570 to 1583, 2024
2. Vanky E et al. Breast size increment during pregnancy and breastfeeding in mothers with polycystic ovary syndrome: a follow-up study of a randomised controlled trial on metformin versus placebo. BJOG 119:1403 to 1409, 2012
3. Nommsen-Rivers L et al. Feasibility and acceptability of metformin to augment low milk supply: a pilot randomized controlled trial. J Hum Lact 35(2):261 to 271, 2019
4. Kirigin Biloš et al. Polycystic ovarian syndrome and low milk supply: is insulin resistance the missing link? Endocrine Oncology and Metabolism 3(2):49 to 55, 2017
5. NHS. Breastfeeding: is my baby getting enough milk?, reviewed April 2026
6. NHS. Breastfeeding and diet, reviewed May 2026
7. NHS. Metformin: pregnancy, breastfeeding and fertility, reviewed August 2026
8. NHS. Natural family planning (including breastfeeding as contraception), reviewed February 2024
9. Gunderson EP et al. Lactation and progression to type 2 diabetes mellitus after gestational diabetes mellitus: a prospective cohort study. Ann Intern Med 163(12):889 to 898, 2015
10. Tay CT, Teede HJ, Boyle JA, Kulkarni J, Loxton D, Joham AE. Perinatal mental health in women with polycystic ovary syndrome: a cross-sectional analysis of an Australian population-based cohort. J Clin Med 8(12):2070, 2019