Pregnancy Hormones

Understand the vital role hormones play in your pregnancy.


Oxytocin is the hormone that triggers uterine contractions during labour, as well as the practice contractions known as Braxton Hicks. Produced by the pituitary gland in the brain, oxytocin also stimulates the milk glands in the breasts to produce milk.


In the latter stages of pregnancy high levels of (MSH) cause the darkening of the nipples, the dark patches on the face called chloasma, and the dark vertical line down the stomach called the Linea Nigra (translates as black line). These changes in pigmentation are temporary and fade following childbirth.


Progesterone affects every aspect of pregnancy. The ovaries usually produce progesterone, but during pregnancy, the placenta produces it. Progesterone relaxes the smooth muscle in the womb to prevent muscle contraction that could otherwise trigger miscarriage. It also increases body temperature, helps in the production of breastmilk, dilates blood vessels and relaxes muscle in the bladder, bowel and veins so that they are more flexible.


Similar to progesterone, oestrogen is usually produced by the ovaries, but is produced by the placenta during pregnancy. It strengthens and prepares the womb for implantation of the fertilised egg and prepares the breasts for breastfeeding by enlarging the nipples and encouraging the development of milk glands. The high level of oestrogen falls immediately after the birth.


Otherwise known as the happy hormones, these help numb the sensations of pain and stress. The brain throughout pregnancy and during childbirth produces endorphins. After the birth, the levels drop sharply.
Human Chorionic Gonadtrophin (HCG)
HCG passes into your urine and can be detected by a pregnancy test 12-16 days after fertilisation. At this stage the primitive placenta produces it. A high level of this hormone in the first three months is thought to be responsible for morning sickness. HCG stimulates the ovaries to produce more progesterone, which in turn halts the menstrual cycle during pregnancy.

Human Placental Lactogen

HPL is a group of hormones that includes prolactin, oestrogen and progesterone. HPL is responsible for enlarging the breasts and the secretion of the first milk called colostrum.


This is the hormone that softens ligaments and tissues during pregnancy. The elasticity provides increased flexibility in the joints of the lower back and pelvis in preparation for childbirth.

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