During pregnancy, to feed the growing foetus, mum's pulse increases, her heart pumps more blood with each beat and she has 50% more blood. This should cause severe hypertension but amazingly mum's blood pressure drops because her blood vessels relax. We don't understand what controls these changes but sometimes the blood vessels don’t relax causing preeclampsia, and mum’s blood pressure increases threatening both mum's and baby's lives. The only cure for preeclampsia is to deliver the baby, often very early. Surely in today's modern world we can do better! So why not? Since we don't understand what causes mum’s blood vessels to relax normally, we can’t make them relax in preeclampsia. Recently we have shown that tiny packages, called vesicles, that are sent from the placenta into mum’s blood, carry signals that cause her blood vessels to relax and here we will investigate if vesicles change in preeclampsia.