The Investigator would like to see if taking a DHA supplement at a dose recommended for heart health will improve brachial artery dilation (relaxation) and help blood pressure. As a second goal the Investigator would like to see if this supplement can delay preterm delivery by improving heart health. In this research study, the Investigator is asking pregnant women with chronic high blood pressure to take Expecta (DHA - Martek Biosciences, now known as DSM Nutritional Lipil) during the last half of their pregnancy until six weeks after they deliver their baby.