The hormones that are important during pregnancy include human chorionic gonadotropin (or hCG), progesterone, oestrogen, relaxin, oxytocin, prolactin, and a group of hormones called endorphins.

You may experience constipation, nausea and heartburn because of the changes in your digestive system triggered by the hormone levels. Mood changes are also common – you might feel a bit depressed or tearful, or more grumpy than usual. Sometimes these changes can be quite extreme. Many of the hormone levels drop suddenly after the birth – and this can lead to strong feelings of depression.

In early pregnancy

• hCG helps get the womb ready and can produce morning sickness and tiredness.
• Progesterone and oestrogen help release the egg from your ovaries and implant it in your womb, and to increase blood supply.
• Progesterone helps the baby grow – and can cause upset tummies, bloating, sore breasts and legs. Progesterone is also responsible for the fact that your hair is thicker.
• Progesterone helps the breasts to develop ready for lactation and stimulates gland and duct development.
• Progesterone and relaxin relax the uterus muscles to be ready for the baby. Other muscles in your body may also relax because of these hormones, which might make you ache a little, and might affect your pelvic floor muscles, so you need to go to the loo more frequently.

In later pregnancy

• Hormones including oxytocin create that loving “bonding” feeling and can lead to the Mum feeling strong urges to rush around to create a “nest” for her baby.
• Oxytocin hormone triggers labour, as well as stretching the cervix and stimulating the nipples to release milk.
• Oestrogen, progesterone and human placental lactogen (HPL) prepare the breasts for breastfeeding
• Prolactin switches on milk production and also has a tranquilising effect.