Hormones in Pregnancy

We all know that changing hormonal levels can make you feel, quite frankly, like you are LOSING YOUR SHIT sometimes…. But why is this? What hormones are being produced? And how are they actually affecting our bodies and mood?

Hormones are the chemical messengers produced and secreted by glands, which maintain the body’s internal environment. During pregnancy there are huge changes to the levels of different hormones that the body produces. It can feel like, and you literally are in, a state of constant hormonal overload…

Here are the key players in the hormones produced in pregnancy:

HCG (Human Chorionic Gonadatopin) – this is the hormone that is produced shortly after an egg is fertilised by a sperm, and is the hormone detected in the urine by pregnancy tests. It basically is the hormone that signals to your body that you are pregnant and needs to build a nest for the growing embryo. It tells your ovaries to stop maturing an egg each month and stops ovulation. HCG can affect appetite and is associated with nausea and vomiting in the first trimester. It is also partly responsible for the frequent need to pee in the first trimester as there is greater blood flow to the kidneys so they eliminate waste quicker.

Progesterone – the hormone that prepares the lining of the uterus to be invitingly rich and squishy for when a fertilised egg implants. If an egg is not fertilised then the lining sheds away (otherwise known as a period). In pregnancy, progesterone maintains the environment of the uterus and prevents uterine contractions until the baby is ready to be born. It also prevents the production of milk in the breasts until birth. At birth there is a dramatic fall in progesterone and an increase in prolactin, stimulating milk production within a few days. Some women will have leaking from their breasts in pregnancy, but this is generally in small amounts and not the level of lactation that occurs once the baby is born. High levels of progesterone can have a sedative effect and contribute to an altered sleep pattern. It can also increase hair growth, hello luscious locks!

One of the main effects of progesterone is that it relaxes smooth muscle in the body (not just the uterine muscle to prevent it uterus contracting). This can lead to lots of common pregnancy symptoms:

  • Constipation/ gas – the intestine is a muscle so digestion is slower due to the relaxing effect of progesterone on the gut’s movement
  • Acid reflux/ heartburn/ burping/ bloating – the muscles that normally prevent stomach acid coming up are relaxed
  • Dizziness as a result of lowered blood pressure (blood vessels ‘relaxed’ and dilated)


Oestrogen – Plays a major role in preparing the body for lactation (the production of milk in the breasts). It also helps the uterus grow and become more ‘vascular’, which means there can be increased blood flow to this organ that is doing a lot of hardwork. Oestrogen also triggers the development of key organs in the baby such as the lungs, liver and kidneys. At the end of pregnancy, the start of labour is triggered by a cascade of hormones, and oestrogen is responsible for preparing the uterus to respond to another hormone called ocytocin. Oxytocin is the hormone that causes contractions and is truly amazing, so much so that I am saving a whole post on this gem!

Side effects of increased oestrogen:

  • Nausea
  • Increased appetite
  • Skin changes, such as pigmentation
  • The much talked about ‘pregnancy glow’ is attributed to oestrogen
  • Mood swings – by the sixth week of pregnancy the level of oestrogen is around three times that of the highest point in the menstrual cycle
  • Breast tenderness

No need to be a mathematician to see that your hormones rise significantly in pregnancy!

Relaxin – this hormone (you guessed it!) relaxes the muscles, joints and ligaments to allow for the growth that occurs in pregnancy and to make room for the baby. This can lead to some discomfort and pain in the lower back and pelvis as the ligaments almost soften too much and there is less stability in the joints. The pubic bone, called the ‘symphysis pubis’, is actually two edges of bone connected by cartilage binding the pelvis together. As the pelvis relaxes this bit of cartilage gets tugged apart and can cause quite severe pain for some women in pregnancy, known as ‘Pelvic Girdle Pain’. Physiotherapy and gentle exercise such as yoga and swimming can help relieve this or prevent it worsening. Due to the potential hypermobility of your joints in pregnancy it is important to be careful when exercising and being active to reduce the risk of injury.

Progesterone and Oestrogen are the two key players for mood swings, irritability, anxiety and low mood, which is also why we experience Pre-menstrual Syndrome (PMS). The body has to adjust in the first trimester of pregnancy to these hormones significantly rising. However, many women will report that once the body has come through this period of adjustment they feel a renewed sense of energy and vigour! This can be a huge relief from the sheer exhaustion of the first trimester, as this is a time when SO much is happening in the body, but little can be seen externally and most people don’t know you are pregnant yet. Having to cope with this physical, emotional, and psychological upheaval and not feeling able to scream and shout about it can be quite isolating. Try to be kind to yourself, rest when you can and look after your body as best able to. All symptoms associated with pregnancy vary so much person to person, you may find that pregnancy makes you feel great and full of energy, but for a friend they may be suffering and struggling to find the joy in growing a tiny human. Furthermore, there are remedies and things to help with a lot of the issues discussed above, so ask your midwife or doctor for advice as needed.

One thought on “Hormones in Pregnancy

Leave a Reply

Fill in your details below or click an icon to log in:

WordPress.com Logo

You are commenting using your WordPress.com account. Log Out /  Change )

Twitter picture

You are commenting using your Twitter account. Log Out /  Change )

Facebook photo

You are commenting using your Facebook account. Log Out /  Change )

Connecting to %s