The Mechanics of Breastfeeding

As with pregnancy, breastfeeding is controlled by hormones, these work to keep the volume of milk at the right level to nourish your baby, and to let the milk out when your baby wants it. Prolactin is the hormone responsible for producing milk. During pregnancy it stimulates your breasts to develop milk-producing cells and to produce a small amount of milk. Levels are kept low by the hormone progesterone.® This initial, low-volume milk is called colostrum and is there ready for your baby at birth. After her birth progesterone levels fall, which allows the milk levels to rise - referred to as milk "coming in". Your milk then gradually changes from colostrum to mature milk.

Whenever your baby stimulates your nipples prolactin is released to create more milk, so the volume of milk you produce is decided by your baby's feeding pattern. This is why putting your baby to your breast whenever she wants to feed is particularly important initially, to get your milk supply established. Prolactin levels are higher at night, so it is vital that you allow your baby to breastfeed at night in order to fully establish your milk supply. If milk is not removed from the breasts, prolactin levels fall and milk production will eventually cease.

Oxytocin is the other main hormone involved in breastfeeding, and is responsible for ejecting milk from the breasts - the "let-down" reflex. Muscles high up in your breasts contract, squeezing milk down towards your nipples where your baby can get it. Some women are unaware of this; others find it a strange, almost tickly feeling. A few find it slightly painful. Oxytocin also helps your uterus contract, so when you feed your baby in the early days you may feel "afterpains". These are usually stronger for second or subsequent babies.

Oxytocin can be switched on by different stimuli. Feeding your baby raises oxytocin levels, but Just holding your baby also works - as does thinking about her when she's not there. That's why it's possible to express breast milk without your baby present. This hormone is also produced when you make love so you may find you leak milk during sex especially at orgasm. It's best to feed your baby just beforehand if possible and have a towel handy.

Your baby can get quite a lot of milk from what is released by oxytocin. However, she also needs to play an active part in removing the milk, thus stimulating prolactin to produce enough milk for the next feed. Milk left in the breasts contains an inhibiting factor that stops further milk being produced, so even if your baby feeds often, if she cannot get the milk out effectively then your milk supply will fall.

The first, thirst-quenching milk is often referred to as "foremilk", which means "the milk that comes before". If this is all your baby drinks then she will need to feed more frequently as she will not be getting the levels of fat that she needs to grow. She may also get colicky If she is drinking mostly foremilk, as this passes through the gut quickly and may reach the lower intestine before all the lactose is absorbed. If this happens it will ferment and cause discomfort - as well as green, explosive nappies!

Holding your baby so that she can get at the milk effectively is very important, not only in building and maintaining the milk supply but also in extracting the fat-rich hind milk. There are three things to consider: your posture - how you are sitting or lying; your position - how you hold your baby's body so she can reach your breast and attachment - the relationship between your baby's mouth and your breast.