Increasing hormone levels mean that your bowels don't work as well as they normally would to push the food through your body during the 2nd and 3rd trimesters of pregnancy. Your digestive system absorbs more water from the food and this makes your faeces harder and more difficult to pass. You should make sure you are drinking enough fluids and eating plenty of fresh fruit, vegetables and high-fibre foods. If you're concerned about constipation, talk to your doctor or midwife as mild laxatives and fibre supplements can help.
Attribution: BUPA