Health Check: is it safe to express milk before giving birth?

Late in their pregnancies, some women notice colostrum (early milk) leaking from their nipples.

Some hospitals are advising women to collect this milk in the last weeks of pregnancy, ready to give to their newborn baby, if needed. Midwives, doctors and lactation consultants may suggest this in particular to women with diabetes in pregnancy.

Although collecting colostrum before giving birth is not new, it is now more widely promoted. Yet there has been little research on the practice. And some people are concerned that collecting it when pregnant could bring on labour early, potentially increasing the risk to mother and baby.

So is it safe for women to collect their own colostrum while pregnant? And are there some situations that are more risky than others?

What is colostrum and how do women collect it?

Colostrum contains high levels of antibodies, the proteins that not only fight infections but program a baby’s immune system for life. We don’t know why some women’s breasts start producing colostrum in pregnancy; many women won’t have any until after they give birth.

If women are advised to collect colostrum while still pregnant, they usually “express” these early drops of fluid by stimulating their nipples by hand rather than using a breast pump.

The amount women collect varies from nothing, to a few drops, to a teaspoonful or more. They collect it in a syringe or small sterile jar, which they store in the freezer at home. They then bring it (still frozen) to the hospital when they give birth, where it is thawed if needed to give to the newborn baby while he or she is one or two days old.

Why do women collect it?

The most common reason why women consider expressing colostrum early is if they have diabetes in pregnancy, whether that’s existing diabetes or diabetes that only came on while pregnant (pregnancy-onset or gestational diabetes).

Before birth, all babies receives a continuous supply of food in the form of glucose from their mother. This stops suddenly at birth and as babies transition to life outside the womb they have a period of low blood sugar (hypoglycaemia).

However, this adaptation to outside life takes longer for babies of mothers with diabetes. About one in four or five of these babies develop hypoglycaemia soon after birth. If untreated, this could cause seizures or brain damage.

To treat hypoglycaemia these babies are often supplemented with infant formula since mothers’ milk does not “come in” for a couple of days after birth.

While breast milk is much better than formula at bringing blood sugar to normal levels, there may not be enough milk in the breast to boost the newborn baby’s blood sugar levels. So babies of women with diabetes are more likely to be admitted to a special care nursery for treatment.

But if the mother has a small supply of breast milk ready to feed the baby – a few millilitres in a syringe or spoon – they could avoid this.

If the mother has collected colostrum before birth, the newborn baby may also be less likely to need infant formula, which has a number of risks to the immature gut. Giving formula based on cow’s milk to newborns may also increase their risk of allergies and developing diabetes themselves.

Other women may want to express milk before giving birth because they had a low milk supply with a previous baby or they know their baby has a medical condition that might make it hard to breastfeed well, like a heart condition.

While there can be short-term benefits to newborn babies from being fed colostrum expressed before birth, no one has studied if there are any longer-term benefits.

There also doesn’t seem to be much difference between the quality of the colostrum expressed before birth and colostrum expressed 24 hours afterwards.

Risks to mother and baby

By stimulating their nipples and expressing milk while pregnancy, women could bring on regular contractions of the womb and give birth early.

This is because nipple stimulation leads to an increase in the hormone oxytocin, which plays a role in both milk let-down and contraction of the womb.

For this reason, women who need a caesarean (for instance if their baby is not “head down” or if they have had previous caesareans), have been advised not to express while pregnant.

Another concern is that stimulating the nipple and the increased contractions could reduce blood flow to the womb. So, expressing while pregnant is not recommended when the foetus is not growing well, or has other medical conditions such as macrosomia (excessive weight), or there is too much fluid in the womb.

Is it right for me?

Our study results, published today in The Lancet, found that expressing while pregnant is safe for women with diabetes in low-risk pregnancies in late pregnancy (from around 36 weeks). After studying over 600 women, we found no increase in early births or admissions to neonatal intensive care. However, one in four women couldn’t collect any colostrum.

Before our trial, researchers had only run three small studies of expressing colostrum while pregnant, and no randomised trials for women without diabetes.

So, our advice to women with questions about expressing while pregnant is to ask their health care professional about their individual situation. They are best placed to discuss the risks and benefits.