Throughout pregnancy, your blood volume increases progressively causing the kidneys to produce more urine, so you need to go to the bathroom more often.
You’ll also find you’re producing more urine because you’re probably drinking more, which is a good thing – the advice when you’re experiencing morning sickness is to stay hydrated to compensate for the lack of food, which also leads to more frequent trips to the bathroom.
When you’re pregnant, hormones such as progesterone and relaxin help to loosen and relax your muscles, joints and ligaments to allow your body to stretch and prepare for delivering a baby. This also weakens the muscles that control urine flow, so leaks can become more common.
As your uterus expands with your growing baby, there’s extra pressure on your bladder and it can’t expand to the same levels of fullness. The bigger your baby gets, the more your bladder gets squeezed, which is why you might feel you live in the bathroom during your third trimester.
What’s more, when you lie down at night, fluid that has built up in your legs and feet finds its way back into your bloodstream. This increases the production of urine, which is why you might be waking up more frequently at night to pee.