Leon Chesley studied hypertension, or high blood pressure, in pregnant women during the mid-twentieth century. Chesley studied preeclampsia and eclampsia, two hypertensive disorders found in approximately five percent of all US pregnancies. In New Jersey and New York, Chesley devoted over forty years to researching preeclampsia and eclampsia. Chesley conducted several long-term studies using the same group of women beginning from their pregnancies. Chesley’s multi-decade research led to more accurate diagnosis of preeclampsia and eclampsia in pregnant women and significantly reduced the mortality of pregnant women due to hypertensive diseases.

In the 1950s and 1960s, researchers Leon Chesley, John Annitto, and Robert Cosgrove investigated the possible familial factor for the conditions of preeclampsia and eclampsia in pregnant women. Preeclampsia and eclampsia, which are related to high blood pressure, have unknown causes and affect at least five percent of all pregnancies. The researchers, who worked at Margaret Hague Maternity Hospital in Jersey City, New Jersey, used hospital patient records to find and reexamine women who had eclampsia at the hospital, as well as their daughters, sisters, daughters-in-law, and granddaughters. Chesley and colleagues found that the daughters and granddaughters of eclamptic women were more likely than the female offspring of non-eclamptic women to have preeclampsia and eclampsia in their own pregnancies, and especially in their first pregnancies. The study provided evidence that the disorders are inherited, enabling physicians to better monitor pregnancies in women who have a known family history for preeclampsia and eclampsia.