Your body produces hormones all the time; they act as messengers, carrying information between tissues and organs via the bloodstream.1 These hormones attach to specific receptors and enable your body to function as it should.1 During pregnancy, these are particularly important to maintain the health of the mother and child.

There are six key hormones that are essential for a successful pregnancy. They’re produced in different parts of the body and serve very specific functions at different times throughout a pregnancy. They are:1

  • Human chorionic gonadotropin (hCG)
  • Human placental lactogen (hPL)
  • Estrogen
  • Progesterone
  • Relaxin
  • Oxytocin

Human Chorionic Gonadotropin (hCG)

This hormone, also known as hCG, helps to signal to the mother that a fertilized egg has been implanted in the uterus.1 It can be detected in the urine as early as 7-9 days after conception, and it’s what over-the-counter pregnancy tests use to determine a positive result. If you receive a pregnancy test when visiting your doctor or healthcare provider, they’ll be testing for the presence of this hormone as well.2 Human Chorionic Gonadotropin shoulders some responsibility for the frequent urination that some mothers experience during the first trimester; its presence increases blood flow to the pelvic area and kidneys, which triggers the kidneys to eliminate waste more quickly.1 This hormone is produced by the placenta and helps regulate other pregnancy hormones like progesterone and estrogen.1

Human placental lactogen (hPL)

This hormone, also known as prolactin, is made by the pituitary gland and assists in the production of breast milk.3 During a pregnancy, a woman’s prolactin levels rise rapidly—pregnant women may have up to 20 times the amount of prolactin as women who are not pregnant.3 This hormone works in conjunction with oxytocin to encourage bonding and produce breast milk.1 The act of breastfeeding releases more of this hormone into the blood stream, which stimulates further production.1 Women who choose not to breastfeed may find that the levels of this hormone return to normal shortly after giving birth.3


This hormone is vital for a successful pregnancy outcome. In the early stages, it has a few roles that help establish the pregnancy:1

  • Stimulates the growth of blood vessels and increases blood flow to the womb.
  • Stimulates glands within the lining of the womb to produce nutrients that will nourish the implanted embryo.
  • Makes the lining of the womb grow and thicken to support a placenta and allow an embryo to implant and thrive.
  • Helps to establish the placenta, which then produces progesterone throughout the pregnancy.

This hormone also contributes to a range of necessary functions throughout the second and third trimesters. It’s vital for the development of the fetus and helps strengthen the muscles in the pelvic area to prepare for labour.1 Additionally, it actively keeps the muscles of the womb from contracting until labour starts, so not only does this hormone help you get ready to give birth, but it also actually staves off labour until you’re ready.1

Lastly, even though pregnant mothers produce prolactin (hPL) throughout their pregnancies, progesterone prevents them from physically lactating until after birth.1


Estrogen and progesterone tend to work in tandem: the functions of one hormone require the presence of the other. Estrogen is made and released by a woman’s ovaries and is necessary for the placenta to produce progesterone.1

During a pregnancy, estrogen’s role is like that of a foreman, ensuring that things are getting done according to plan.1

  • Estrogen acts as a regulator for other pregnancy hormones and maintains their levels and stimulates their production.
  • It ensures that the organs within the fetus are developing correctly, including the lungs and liver.
  • This hormone helps to regulate the placenta and ensure that it’s growing appropriately to support the fetus.
  • Working in conjunction with progesterone to promote the growth of breast tissue in preparation for lactation.


This hormone is produced throughout a pregnancy but may be detectable by week 7.1 The role of relaxin is to relax muscles, joints, and ligaments in order to make room for a growing baby.1 Since the effects are most pronounced around the pelvic region, pain and discomfort in the lower back and hips may be experienced in some women during the first trimester and their newly relaxed joints may make them feel somewhat unstable on their feet. During labour, relaxin helps to prepare for the baby’s arrival by softening the cervix and allowing for the further expansion of the pelvic joints to make birth easier.1


Oxytocin is frequently associated with feelings of love, bonding, and motherhood, which may explain why it’s referred to as the “love hormone.”1 Levels of this hormone rise at the beginning of a natural labour, which leads to contractions and the softening of the cervix.1 However, if labour is not progressing as it should and a mother needs to be induced, a synthetic oxytocin will be used to stimulate contractions, open the cervix, and move the baby into the birth canal.4

Postpartum Hormone Changes

After the baby arrives, women may experience a range of emotions, some of which may be attributed to the rapid drop of hormones after childbirth.5 These mood changes are commonly referred to as the baby blues and may affect 15-84% of new mothers.5 Hormonal changes during labour and the postpartum period that may affect a mother’s mental and emotional well-being may include:

  • A dramatic drop in progesterone occurs immediately after birth, which may play a role in postpartum depression.6 An imbalance may be in effect until this hormone is secreted again, which will not happen until a mother’s first menstrual cycle after giving birth.6
  • During pregnancy, concentrations of progesterone increase up to 18 times their normal levels, and estrogen levels are multiplied by up to 1000 times but return to their pre-pregnancy level within a few hours of giving birth.7 The removal of the placenta causes women to immediately experience a huge drop in their estrogen and progesterone levels.7

Reproductive hormones likely play a role in postpartum depression (PPD) based on of the association between the rapid change in hormone concentrations and the timing of onset of depressive symptoms.8 These hormones have a function in the processing of basic emotions, cognition, and motivation.8 Some women may be more sensitive to the hormone changes following pregnancy, putting them at higher risk for PPD. 8

Hormone changes are part of life, pregnancy, and childbirth. Learning what’s happening inside your body may help explain how you’re reacting to things and feeling the way you’re feeling. Talk to your doctor, midwife, or healthcare provider if you feel like something out of the ordinary is happening, and if you feel any pronounced negative mood shifts after your baby arrives, ask for support from family and friends. If you feel that you require medical help during any part of your pregnancy or the postpartum period, reach out to your doctor.