We all have lots of different hormones circulating in our bodies, but the types and amounts of these hormones can change a lot during pregnancy. Why are pregnancy hormones important and what kind of changes should you expect?

What Hormones Change in Pregnancy?

A hormone is a messenger that moves around your body. When it reaches certain types of cells or organs, it can tell them what to do. You might know a bit about the way hormones can affect your body during your menstrual cycle. Changes in the levels of hormones such as oestrogen and progesterone over the month can affect everything from your mood to your digestion. You’ve probably noticed that these effects can change from one cycle to the next and that your friends don’t always have the same experiences. Hormones can have complicated effects on many different parts of the body.

During pregnancy, your hormones can have even stronger effects and you’ll be exposed to some new hormones that are only produced when you’re expecting:

  • Oestrogen: produced by the early embryo and then the placenta, its levels rise during the first trimester and then remain steady. Oestrogen plays an important role in the baby’s development.

  • Progesterone: levels rise throughout the first trimester and then stay steady. It looks after your uterus and ensures your immune system doesn’t try to attack the baby.

  • Human Chorionic Gonadotropin (HCG): produced by the placenta (and its precursors) throughout pregnancy, it is at its highest levels at day 60-90 and is responsible for many of the early signs of pregnancy, including morning sickness. Pregnancy tests usually check for HCG in your urine.

  • Prolactin: gets your breasts ready to produce milk.

  • Relaxin: relaxes your joints so that your body is able to give birth.

  • Oxytocin: your uterus becomes very sensitive to this hormone as the birth gets closer, so it can trigger labour. Oxytocin also helps to prepare the cervix, stimulates milk production, and encourages bonding with your baby.

How Can Pregnancy Hormones Affect You?

Just as women can have different experiences during their menstrual cycles, we can also have very different experiences of pregnancy hormones. You might notice some of the following:

  • Morning sickness

  • Other digestive symptoms including heartburn, constipation, and bloating

  • Needing to urinate more often

  • Changes in blood flow that can cause dizziness or low blood pressure

  • Skin changes, including the “pregnancy glow” that some women experience, but also problems such as spots and pigmentation changes

  • Hair growth, for example on your breasts or belly

  • Looser joints (especially near the end of pregnancy)

  • Tender and larger breasts

  • Changes in your mood, especially during the first trimester

Although some of the effects of pregnancy hormones can be uncomfortable, they are also helping your body to carry your baby and get ready for the birth.