The Roles of Hormones in Pregnancy

There are many different hormones that all play a really important role in your pregnancy, from before you become pregnant to after you have given birth! Hormones play a role in preparing your body for pregnancy and birth and can affect your mood and even your appetite! Here is a short guide to the different hormones in pregnancy.


hCG – Human Chorionic Gonadotropin

You only have the hormone hCG in your body when you are pregnant.

hCG is incredibly important in early pregnancy as hCG helps the uterus lining stay in place, it supports implantation of the egg into your womb, and starts the production of oestrogen and progesterone! hCG is the hormone that is typically linked with morning sickness as it’s believed the rising levels of hCG stimulate the area of the brain responsible for morning sickness.

Human Chorionic Gonadotropin (hCG) levels rise rapidly in the first few weeks of pregnancy, and because hCG is usually only produced during pregnancy (by the fertilised egg!) hCG is what makes a pregnancy test positive!



In early pregnancy, oestrogen supports the baby until the placenta is developed. Oestrogen helps develop the placenta and the network needed to take waste to and from the developing baby. Oestrogen also helps to trigger the development of foetal organs!

In the mother, increased oestrogen helps to expand and maintain the uterine lining and increase blood flow to the uterus. Because oestrogen triggers an increase in blood volume, it can cause nausea, swelling and tender breasts.



Before pregnancy, progesterone thickens the uterine lining in preparation for the fertilised embryo to embed. During early pregnancy, hCG signals to the ovaries to continue to produce progesterone, which prevents the shedding of the uterine lining for implantation and prevents the release of another egg! Progesterone also increases a woman’s appetite, to increase nutrients available for the baby!



After ovulation, relaxin prevents uterine tightening to encourage implantation of the fertilised embryo. Relaxin also prevents labour tightening during pregnancy to prevent premature childbirth.

Relaxin regulates the mother’s cardiovascular system, by relaxing the mother’s blood vessels to increase the blood flow to the placenta and kidneys to adapt to the increase in need for oxygen and nutrients!

To prepare for childbirth, relaxin softens the cervix and relaxes the ligaments in the front of the pelvis to ease the birth of the baby!


During the first trimester, oxytocin increases the metabolism of the mother to help her gain weight to store nutrients for the growing baby!

During the third trimester, oxytocin is linked to encouraging a woman to act more carefully to protect herself and the baby!

Oxytocin causes uterine tightening during labour and helps you relax after giving birth! Oxytocin produced during skin to skin with your baby helps create the bond between mother and child!


Prolactin helps breasts to grow and develop during pregnancy in preparation to breastfeed and helps to stimulate milk production after birth! Prolactin also helps mothers to not become pregnancy again when she first begins to nurse by blocking egg production!

Prolactin is also known to affect dopamine (the happy hormone) and as a result may be a contributing factor towards postpartum mood and energy changes!