Assoc Prof Dr Harlina Halizah Siraj: ‘The hormones are important to prepare a woman’s body for breastfeeding and to sustain lactation.’

Assoc Prof Dr Harlina Halizah Siraj: ‘The hormones are important to prepare a woman’s body for breastfeeding and to sustain lactation.’


WOMEN who are pregnant know that they undergo changes in their hormone levels, and when they go through childbirth there is a dramatic change again.

Exactly what roles do hormones play as a woman prepares to welcome a new baby?

“The hormones are important to prepare a woman’s body for breastfeeding and to sustain lactation,” said Assoc Prof Dr Harlina Halizah Siraj, obstetrician and gynaecologist at the Universiti Kebangsaan Malaysia Medical Centre, at the recent PRISMA 2015 conference.

She spoke on “Is it All About the Hormones?” at the two-day conference organised by the Malaysian Breastfeeding Peer Counsellor Association.

Hormones are chemical substances produced in the body and they control, regulate and fine-tune the activity and function of certain cells and organs. These are secreted by special glands. For example, the thyroid hormone is produced by the thyroid gland.

In pregnancy

Prof Dr Harlina explained that the Human Chorionic Gonadotropin (HCG) hormone is very high in the first trimester. In some women who are very sensitive, this can cause a lot of morning sickness. The HCG hormone is there to maintain the corpus luteum (a temporary endocrine structure needed for ovulation and early pregnancy).

There is also an increase of oestrogen and progesterone during pregnancy. “Oestrogen is the hormone that makes you look flushed and glowing,” explained Prof Dr Harlina.

These are the placental hormones and their actions:

  • HCG – maintains the corpus luteum.
  • Progesterone – maintains the uterine lining and inhibits the uterine contraction.
  • Oestrogen – maintains the uterine lining and stimulates the mammary glands.
  • Placental lactogen – stimulates the mammary glands and supplies energy to the foetus.
  • Parathyroid hormone-related protein – increases the blood calcium.
  • Relaxin – softens the cervix, tissue and ligaments and weakens the pubic symphysis.
  • Corticotropin-releasing hormone – fine-tunes the heart rate, blood pressure, blood glucose and stimulates labour (without this hormone you won’t be able to adapt to the demands of having another human being inside you).

During breastfeeding

Explaining how the hormones work during breastfeeding, Prof Dr Harlina said, “The infant’s suckling stimulates the hypothalamus. The hypothalamus then signals the pituitary gland to release the oxytocin and prolactin. The oxytocin stimulates the release of milk while the prolactin stimulates milk production.

“That’s why it is so important for baby to suckle because that will activate the whole process,” she said.

Hormones in breastfeeding:

Prolactin – This is the hormone that signals the body to make more milk. It is known as the milk-making hormone. When you are pregnant, it starts to pour in.

This is also known as the hormone of submissiveness, anxiety and vigilance, or, the “mothering hormone”. This hormone keeps you awake and wakes you up when your baby makes a slight noise.

Prolactin very much depends on the suckling. The secretion continues after a feed, to produce milk for the next feed. More prolactin is secreted at night. This is also the hormone that suppresses ovulation.

Oxytocin – This is the milk-ejection hormone. When the nerves in the areola are stimulated (through suckling), the brain sends a signal to the milk-making cells to contract and send milk to the baby.

Oxytocin has been known to increase when you hear a baby cry, you smell your infant, or when you see your baby.

When the oxytocin is really abundant, it will contract the alveoli of the glands in the breast. When this happens, you don’t need to express a lot, as the mammary glands will contract and the milk will be easily secreted. This explains the letdown reflex.

In fact, you can produce more oxytocin if you stimulate the nipple.

Prof Dr Harlina was full of praise for the oxytocin hormone.

“Oxytocin is not just for milk production. For me, it serves other functions as well. If your oxytocin is not working for you, having so much prolactin doesn’t really do much good.

“In fact, it is called the hormone of love. It has been well established that oxytocin is released during sexual activity, through orgasm, during birth and during breastfeeding. It gives you that feeling of love and altruism.

“Oxytocin has also been found to make you more courageous, eliminates fear and encourages trust,” she added.

Among the factors that cause the release of oxytocin are nipple stimulation, feeling of security, chocolate, soft music and massage.


Although mothers are often told that if they are breastfeeding, they cannot become pregnant, Prof Dr Harlina said this is not true.

If you are breastfeeding but your menses has returned, you can conceive. How will you know when you should use contraception, if you do not want to become pregnant so soon?

You will need to use contraception if:

  • Your menses has returned.
  • You are supplementing regularly or allowing long periods without breastfeeding.
  • Your baby is more than 6 months old.

No additional contraception is necessary if:

  • Your menses has not returned.
  • You are not supplementing regularly nor allowing long periods without breastfeeding.
  • Your baby is younger than 6 months old.

During her presentation, Prof Dr Harlina addressed the question on whether a mother can continue breastfeeding after she becomes pregnant.

In a study done in Italy and published in 2013, it was found that:

“No evidence indicates that pregnancy breastfeeding overlap might cause Intrauterine growth restriction (IUGR) particularly in women from developed countries. Little information is available on the composition of human milk of pregnant women, and we found no data on the growth of infants nursed by a pregnant woman.

“However, both the composition of postpartum breast milk and the growth of the subsequent newborn appear to be partly affected, at least in developing countries. We support breastfeeding during pregnancy in the first 2 trimesters, and we believe it to be sustainable in the third trimester. Based on the hypothetical risk, caution may be warranted for women at risk of premature delivery, although no evidence exists that breastfeeding could trigger labour-inducing uterine contractions.”

In simple terms, the study says that breastfeeding during the first two trimesters should be okay as there is no proof that breastfeeding affects the development of the unborn child. In the third trimester, it is believed to be sustainable, however those at risk of premature delivery should practise caution.

Prof Dr Harlina’s advice is to plan and space out pregnancies so that mothers don’t get pregnant while still breastfeeding. This way, the mother can devote enough time to breastfeeding each child.

“No pregnancy should be unplanned and unintended,” she said.


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