Mar 02

What You Need To Know

The Biology Of Breastmilk Feeding

Breastmilk feeding of infants is a common characteristic of all mammals.

Like reproduction, optimal infant nutrition is a key element of the survival of our species!

We tend to think of mother’s milk as a food – a purely nutritional – milk source.

Human milk is way more complex and is actually a living tissue – more like blood than food- that mother makes for her baby.

Many mammalian newborns (like newborn calves) cannot survive if they don’t get the immune factors from colostrum (first milk) after birth.

That’s how amazing mothers’ milk is.

The development of the breast and its ability to make milk is super interesting.

Check out this great video about the Physiology of Breastmilk.


The breast starts to develop in utero, in response to pregnancy hormones.

Things settle down then until puberty when the breast starts to mature and grow, going through several stages of development.

During pregnancy, the breast finishes its milk production development, enlarging in size from stimulation of hormones and growth factors from the placenta.

The hormones of pregnancy (made by the placenta) keep milk production down to a very low level before delivery.

By the end of pregnancy the breast is making about an ounce of milk a day- but it may not be obvious to the mother – as much of the milk is absorbed back into the bloodstream.

After delivery, the placental separation to mother is severed, these hormone levels fall, and milk starts to be produced.

At first there are just drops of colostrum; rich in protein, glucose, and antibodies.

Over the first days milk production grows and fat and more milk sugar is put into the milk.

Knowing that milk production is a process and not something that magically happens after baby is born can help mothers understand why her breasts are not full immediately.

Humans are the only species that don’t have a lot of milk right away, and we really don’t know why that is.

There is still much that is not known about human breastmilk.

Give The Gift Of Milk To Your Baby

Breastfeeding is a wonderful bonding experience that comes with an abundance of benefits for mother and baby.

It is a natural process, but one that mother and child must learn together.

Educate yourself about the biology of mothers’ milk, how the infant gets milk from the breast, and ways you can get off to a good start after delivery.

Women have been breastfeeding for millennia and you can too.

Get Informed

Read these tips before you have your baby, so that you know what to expect and how to get a good start.

Watch Breastfeeding in the ‘First Hours After Birth’ to see how people around the world are keeping babies close to mother and starting breastfeeding right after delivery.

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If all is well, doing the most natural things, and getting back to basics will help mothers around the world to be successful with nursing their babies.

If you have questions about your own health condition, medications, or infections, check with your obstetrician or consider a prenatal pediatric consult.

Click here for informative materials on many medications.

Get An Early Start

We encourage mothers to hold baby skin-to-skin at delivery and allow baby to start breastfeeding when they are ready.

It can be right away, or after you recover a little.

Some babies will nurse a long time and then nap for a few hours, others will nurse off and on, and some babies just sleep after delivery- they can be exhausted.

Know that this is all normal and we recommend you watch your baby and follow their lead if all is well.

Some small, premature or babies with risk factors for low glucose or poor feeding may need to be encouraged to feed within an hour of delivery; your nurse or doctor will let you know if this is needed when that time comes.

Watch ‘Carrying Your Baby Skin-to-Skin’ to see how mothers around the world carry their babies skin-to-skin. Although this video features small babies, skin-to-skin is something we encourage all parents to do.

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Get Some Data

Keeping a record of your baby’s feedings and dirty diapers may help you know that your baby is doing well.

Many hospitals will provide you with a log book to record feedings, wet and dirty diapers for the first days.

Since each day is very different, early on this can be helpful.

Consider downloading a baby feeding App before you go to the hospital if you find this easier than paper.

Click here to view the UC San Diego Health Breastfeeding Guide and logbook. En Español.

Get Support

Delivery can be exhausting and most mothers find having their partner, family or a friend at their side to be a great help.

Expect to need around the clock help for those days in the hospital and first week or so at home.

Most women stay 1-2 days after a vaginal delivery and 3-4 days after a Cesarean delivery in California.

Many hospitals have a bed or couch in mothers room for the helper to sleep on. Consider bringing an air mattress if they do not have a sleeping surface for your partner.

If you have additional helpers giving your partner an afternoon break to sleep soundly at home and come back to the hospital to face the night with you rested is something to consider.

Remember, somebody has to be safe to drive you all home!

Get Prepared For…. Baby Night Owl

Newborns sleep for most of their first 24 hours as they recover from the delivery. (There are always exceptions.)

During the second and third nights, most babies will wake up and cry more often. They may seem to be hungry constantly.

This normal behavior is displayed by both breastfed and formula-fed babies.

Newborns cry more during the night to make sure they receive adequate care and nutrition during a time when their mothers and caregivers are sleepy. (Smart babies!)

If your newborn displays hunger cues (sticking out tongue, lip-smacking, rooting), then latch them on to breastfeed.

Call your nurse if you need assistance.

If your newborn has recently completed a great feeding and still seems unhappy, then try the soothing techniques listed below.

Learn How To Soothe Your Baby

Hold your undressed baby next to your bare chest. Babies stay warm and are calmed by your heartbeat when held skin-to-skin.

Make sure baby’s nose is not covered and their skin stays pink.

If you are sleepy or asleep, your baby will be safer when placed in the bassinet.

Swaddle baby snugly (but not too tightly). Most babies will stay calmer longer and sleep better if their arms are swaddled straight down along their body.

If you can slip two fingers between the blanket and your baby’s chest, then baby has enough room to breathe.

Check out this great video about swaddling.



Allow baby to be un-swaddled some times during the day when baby is awake and happy, and limit swaddling to brief sessions after 2 months of age.

Hold infant in your arms so they are on their side or tummy.

When a baby is upset, holding or placing them on their back can make them more upset.

Babies should always be placed on their backs for sleep or when left unsupervised.

Offer baby something to suck on (mother’s breast or a clean or gloved finger). Sucking causes endorphins or “feel-good” hormones to be released in babies’ brains.

Rock or sway your baby or pat thier back while holding them.

Babies miss the constant movement and floating they experienced in the uterus.

Say ‘shhhhhh’, talk and sing to them, or play music or white noise.

Babies are familiar with the loud music of their mothers’ heart, pulsing vessels and intestines.

Consider watching Dr Harvey Karp’s videos about ‘Happiest Baby on the Block’ and infant soothing.

Get Prepared For The Hospital

When you are packing your bags for the hospital you might wonder if you need anything for breastfeeding.

Luckily, you and your baby have all you need with no special equipment required!

If you need to pump in the hospital the nurses will give you the equipment you need.

Arranging a pump before you deliver is a good idea for moms who are going back to work, but you don’t need to bring it to the hospital.

Hospitals are generally stocked with lanolin ointment and nipple shields if they are needed.

Think about leaving pacifiers at home, we recommend that for the first weeks anytime the baby wants to suck, that you nurse and not have baby waste energy on the plastic pacifier.

Pacifiers can encourage the baby to clamp down or bite too; so hold off until nursing is comfortable and going well.

Some mothers do find a nursing gown or special bras helpful, but getting the right size is often best judged after your milk comes in.

The hospital has plenty of gowns and after deliver you probably don’t want to use your own as they get soiled frequently.

Lisa Stellwagen MD, FAAP  Professor of Clinical Pediatrics at UC San Diego Health
Tia Hubbard MD FAAP at UC San Diego Health
Carol Sainz RNC IBCLC at UC San Diego Health
The American College of Obstetricians and Gynecologists. (2016). Labor, Delivery, and Postpartum Care: Breastfeeding Your Baby [Pamphlet]. Washington, DC.
U.S. Department of Health and Human Services, Office on Women’s Health. (2011). Your Guide to Breastfeeding. [Brochure]. Washington, DC.
UC San Diego Health. Breastfeeding Guide and Logbook. [Brochure]. San Diego, CA.
Special Thanks To Global Health Media Project For Sharing Their Important Work Around The Globe.
Physiology of Breastmilk courtesy of