Heart rate slows, peripheral blood vessels contract, blood pressure rises, and organs adjust their operations. Instead, the scientists found that blood pressure was the big divider. However, the blood pressure finding was a surprise. A jubilant Haenyeo proudly raises her catch at the 5th annual Haenyeo Diving Festival on Jeju Island, South Korea. But during pregnancy, blood pressure disorders like preeclampsia pose a particularly acute risk for both mother and child.