A guide to your body during pregnancy and birth – how it changes and grows and what the different hormones do. Your body during pregnancy – hormones As soon as the placenta starts to form and the cells, which are fast becoming your baby, have implanted into the side of the uterus, your baby will produce human chorionic gonadotrophin (hCG) – these levels will double every couple of days, reaching its peak by about 10 weeks when the levels start to level out as the placenta starts to function. Oestrogen – This hormone is needed to:*stimulate the placenta – to ensure it grows and works *develop your baby’s lungs, liver and kidneys*work with progesterone to grow your breast tissue for milk production The rapidly growing levels of oestrogen in early pregnancy may cause sickness and nausea. Oestrogen and relaxin creates the loosening of the ligaments and joints throughout the body. This is needed to enable your body to expand for your growing baby and to provide the space for your baby to be born. Progesterone – This is a powerful hormone and …