Deep vein thrombosis Formation of a blood clot (thrombus) in one of the deep veins, usually in the leg, resulting in partial or complete obstruction of the blood flow. Eclampsia A convulsive condition associated with pre-eclampsia. Gestational hypertension New hypertension presenting after 20 weeks without significant proteinuria. Hypovolaemia Low circulating volume due to fluid loss commonly caused by haemorrhage. Placental abruption Normally sited placenta separates either partially or wholly from the uterine wall causing haemorrhage and fetal distress. This may also be known as abruptio placenta . Placenta praevia The placenta is sited in the lower segment of the uterus. Type IV placenta praevia will be situated over the internal cervical os.