We compared patterns of blood pressure (BP) change among normotensive women, women who developed gestational hypertension or preeclampsia, and women who had essential hypertension to examine how distinct these conditions are and whether rates of BP change may help to identify women at risk for hypertensive disorders. We used antenatal clinic BP measurements (median, 14 per woman) of 13016 women from the Avon Longitudinal Study of Parents and Children who had a singleton or twin live birth surviving until ≥ 1 year. Linear spline models were used to describe changes in systolic and diastolic BPs in different periods of pregnancy (8-18, 18-30, 30-36, and ≥ 36 weeks' gestation). Women who had essential hypertension and those who developed gestational hypertension or preeclampsia had higher BP at 8 weeks' gestation (baseline) compared with normotensive women. The decrease in BP until 18 weeks was smaller in gestational hypertensive compared with normotensive pregnancies. BP rose more rapidly from 18 weeks onward in gestational hypertensive and preeclamptic pregnancies and from 30 weeks onward in essential hypertensive compared with normotensive pregnancies. Women who developed preeclampsia had a more rapid increase in BP from 30 weeks onward than those who developed gestational hypertension or had essential hypertension. Our findings indicate notable patterns of BP change that distinguish women with essential hypertension, gestational hypertension, and preeclampsia from each other and from normotensive women, even from early pregnancy. These distinct patterns may be useful for identifying women at risk of developing a hypertensive disorder later in pregnancy.