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Milk supply – What to expect and how milk supply works 

Written by Jennifer Clark (IBCLC), Kaya Thorpe (IBCLC) and Lucy Lowe (April 2024) 

How does making milk (lactation) and milk supply work? 


Colostrum (your first milk) is made in the breasts from around 16 weeks' gestation. 

Between 3-7 days after birth, milk transitions from colostrum to transitional milk. Parents maybe be able to roughly pinpoint when their milk transitioned through changes in the breasts (generally feeling fuller, milk turning from yellow to white).  


A baby's stomach size is small and in the first 24 hours feeds are around 5-7mls, slowly increasing to 20-30mls by day 3, 45-60mls by day 7 and by day 30 80-150mls.  


A small weight loss is expected on days 3-5 as milk comes in and breastfeeding is established (up to 8% loss is considered within normal). Weight loss of over 8% means some extra support and monitoring is usually required.  Babies are born with extra fat stores to cope with learning to feed in the first few days and recover from birth, they should do well from this point onwards. 

Parents may feel engorgement or feel fuller, they may have leaking and be uncomfortable when milk starts to come in. Their breasts should soften after a feed or pumping session. For some, engorgement will last a while, for others it could be a few days. Those who have breastfed before may not experience engorgement for as long. If they are tandem feeding, their older toddler/child can help to relieve the engorgement by feeding. 


Possible reasons for a delay in milk “coming in” or low supply 

  • First baby  

  • Obesity 

  • Diabetes 

  • Prematurity 

  • Hypoplasia (insufficient glandular tissue) 

  • PCOS and other hormonal issues 

  • Placenta retention 

  • Caesarean section, long labour, effect of pain relief in labour 

  • Postpartum haemorrhage 

  • IVF pregnancy 

  • Traumatic birth 

  • Breast surgery 

  • Separation from baby and little/no breast stimulation 

What is typical in the early days?  

Normal newborn behaviour 

  • Feeds 10-12+ times a day 

  • Show they are hungry through putting hands to their face/mouth, making little noises, eye movements, moving head. Aim to breastfeed at these first signs of hunger as it is harder to feed a baby who is over hungry. 

  • Allow unlimited time at the breast when sucking actively (hearing regular swallows) and offer the second breast each feed. 

  • Babies may be very sleepy in the early days and need to wake up every 2-4 hours. 

  • May cluster feed for 2-3 hours before a longer stretch of sleep (usually after 6 weeks). Cluster feeding and fussy evenings – normal in the first 3-4 months.  

  • Growth spurts – 7-10 days, 2-3 weeks and 4-6 weeks (Warning – May feel like every week!) 

What are the positive signs that things are going well?  

  • Appropriate wet and dirty nappies (1 per day of life until day 5 when they should be getting heavier and at least 5-6+ per day, 2 stools minimum per day, moving from black to yellow by day 5-7)  

  • No concerning weight issues between days 3-5 – baby’s weight loss should be under 8%. 

  • A happy, settled baby where feeding is comfortable, and parents don’t feel too overwhelmed by life with a newborn.  

  • Once milk comes in, parents should be able to hear or see periods of swallowing during a breastfeed. Baby should be back to birthweight by around 2 weeks and gaining around 25-30g per day. 

Regulation of milk production 
(a coordinated dance between mother and baby)  

Demand and supply = an infant driven system 

What milk the baby removes is then replaced. If all the available milk is removed and the baby is asking for more by suckling, then more will be made.  

The milk factory has a certain overall rate of milk production but responds to short term changes (sickness, teething etc.)  = regulation 

Milk production experiences can change from baby to baby, for example, baby boys tend to stimulate a greater milk volume as they grow a little faster than girls. 

Golden rule of milk production = the more often the factory warehouse (the breast) is emptied, and orders are coming in (breast stimulation), management will hire new workers and speed up production lines. New machinery (breast tissue) may even be added. 

Alternatively, if the warehouse is consistently overflowing, management will slow down the assembly line. If new orders don’t come in, then the factory will be downsized, and it will reduce assembly lines and workers. If no milk is being removed permanently then the factory will close (involution).  


AN EMPTY BREAST= always better for milk production than a full breast! 

 Further explanation - 

What can you expect after 6 weeks?  

After 6 weeks, parents should feel they have found a bit of a rhythm for breastfeeding on most days.  

  • Baby should track or remain within 2 squares of their growth centile when weighed.  

  • Feeding should be comfortable 

  • Babies should be settled most of the time and have periods of sleep – it is normal for babies to be happiest within a parent’s arms.  

  • Some babies may poo less often due to the change in composition of milk, but this should be in a regular pattern (if very irregular ensure regular weighing, and that nappies and weight gain is appropriate).

What concerns us? 

  • A baby who isn’t happy at the breast 

  • Low nappy output/poor weight gain (less than described above) 

  • Consistent unsettled behaviour 

  • Dropping two centiles or more on growth chart 

  • A baby who is unsettled, doesn’t breastfeed for comfort, is often sick and produces green nappies which can be frothy 

  • A breastfeeding parent who is not enjoying breastfeeding at all 

What can affect milk supply? 

Primary factors are factors that impact on the ability to make adequate volumes of milk that occur before birth. Secondary factors impact the ability to make adequate volumes of milk after birth.  

Primary factors  

  • Sufficient glandular tissue- The preparation for lactation starts during puberty. Unlike most mammals, humans' breasts develop in stages and finish their development during pregnancy. Glandular tissue is the tissue that contains the milk making cells. Glandular tissue should be there regardless of breast size and not linked to the size of your breasts. However, the shape of the breast can indicate limited glandular tissue. Not having enough glandular tissue can cause issues with milk supply. This can be known as hypoplasia or insufficient glandular tissue (IGT). It can impact one breast or both. People with hypoplasia can vary in how much milk they can make and often can produce more milk with subsequent babies. 

  • Intact nerve pathways and ducts - The nerves pathways in the breast are crucial for making milk. If there has been any damage to the nerves and ducts via injury or surgery (such as breast implants or breast reduction), this can cause issues for the milk-making messages being transmitted around the body. 

  • Adequate hormones and hormone receptors - Hormones are crucial for breast development and lactation. Pregnancy triggers a large spike in oestrogen, progesterone, prolactin, human placental lactogen (hPL), human chorionic gonadotropin (hCG) and growth hormone. Other key hormones include insulin, cortisol and thyroid hormones. Each hormone will have a corresponding receptor which they unlock. If you have a mismatch between the amount of hormones and receptors, problems with milk production may occur. 

Secondary factors 

  • Adequate lactation-critical nutrients - This means having an appropriate diet to enable you to make milk. This means that potentially your diet could impact your supply. For most of us, we eat enough, even if you eat your calories in chocolate! Milk making uses the parent's energy (approximately 500kcal per day when exclusively breastfeeding a baby under 6 months) T But for some parents, milk making can be inhibited by dietary factors such as a poor vegan/vegetarian diet, having had a gastric bypass, special diets such as keto, low calorie, or having an eating disorder.  

  • Frequent, effective milk removal and breast stimulation- Soon after birth breasts need to be stimulated via either feeding, hand expressing or pumping. This also needs to be done effectively (8-12 times in 24 hours). This means that not breastfeeding effectively (or pumping post birth if baby is not breastfeeding effectively) can impact on milk supply. Additionally, if a breast pump is not being used effectively then milk supply can be compromised. 

  • No other lactation inhibitors - this covers a huge range of issues that can impact on milk making including a large blood loss (known as a post-partum hemorrhage), traumatic birth, early separation of parent and baby, certain medications.  Pregnancy, menstruation and contraceptives can lower milk supply.

(Making More Milk, Maresco and West) 

In theory, if these things are in place, we should see good milk production. 

What is a normal milk supply? 

  • Breasts that feel comfortable after a feed 

  • As milk supply regulates (typically from around 4-6 weeks onwards), breasts that are mostly soft and comfortable 

  • A baby who is content most of the time post a breastfeed, is gaining weight well and is settled at the breast 

  • Leaking between feeds or not leaking is not a sign of a good or bad milk supply! 

IF you need to increase milk supply: 


  • If oversupply is going to occur, it tends to be after 6 weeks of birth 

  • Some parents will naturally have a much higher milk supply. This is fine if it is not causing any issues.  

  • Blockages, mastitis and abscesses can occur for the breastfeeding parent.  

  • Babies can struggle to feed, be uncomfortable, vomit a lot and be unsettled. Green nappies may occur 

  • Oversupply may also cause a fast letdown of milk  

  • Upright positions for baby, using gravity to slow flow down by mum laying back can all help baby cope with fast letdown. 

  • If you feel you have an oversupply, and it is causing issues please see a breastfeeding specialist. 

Resolving oversupply can include: 

  • Ensuring breastfeeding is going well 

  • Block feeding,  

  • Over the counter medications such as pseudoephedrine or GP prescribed medication (Note that medications to reduce supply should only be used as an option in conjunction with support from a breastfeeding specialist) 

  • Blood tests to assess hormone levels.  

  • Tight bras/binding breasts is NOT recommended 



  1. Contraception and Breastfeeding - The Breastfeeding Network 

  1. Emergency hormonal contraception and Breastfeeding - The Breastfeeding Network 

  1. Reasons for Low Milk Supply - Breastfeeding Support 

  1. No Breast Milk After Delivery - Breastfeeding Support 

  1. Droplet » Science ( 

  1. Sheehans Syndrome - Pituitary Foundation  

  1. What is a Galactagogue? - Breastfeeding Support 

  1. DIY Supplemental nursing system | My Site ( 

  1. Peridontal Syringe use | My Site ( 

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