Vitamin D for Preventing Recurrent Preeclampsia in Pregnant Women

The goal of this clinical trial is to find out whether giving vitamin D to pregnant women who had pre-eclampsia in a previous pregnancy helps prevent the condition from coming back. The main question it aims to answer is: Does vitamin D supplementation reduce the chance of pre-eclampsia recurring in pregnant women with a history of pre-eclampsia? To answer this question, pregnant women attending the antenatal clinic at the Department of Obstetrics and Gynaecology, Nishtar Hospital Multan will be invited to join the study. Participants will be randomly assigned to two equal groups: * Vitamin D group: will take 4,000 IU of oral vitamin D until 36 weeks of gestation. * Placebo group: will receive a pill identical in appearance, taste, and consistency but without vitamin D. While on the study medication, each woman will visit the clinic every two weeks. At each visit, her blood pressure