Abstract—Low socioeconomic status has been associated with pre-eclampsia. The underlying mechanism, however, is unknown. Preeclampsia is associated with relatively high blood pressure levels in early pregnancy and with an absent midpregnancy fall in blood pressure. At present, little is known about the associations among socioeconomic status, blood pressure level in early pregnancy, blood pressure change during pregnancy, and pre-eclampsia. We studied these associations in 3142 pregnant women participating in a population-based cohort study. Maternal educational level (high, midhigh, midlow, and low) was used as an indicator of socioeconomic status. Systolic and diastolic blood pressure was measured in early, mid-, and late pregnancy. Relative to women with high education, those with low and midlow education had higher mean systolic and diastolic blood pressure levels in early pregnancy; this was explained largely by a higher prepregnancy body mass index. Although women with high, midhigh, and midlow education had a significant midpregnancy fall in diastolic blood pressure, those with low education did not (change from early to midpregnancy: -0.38 mm Hg; 95% CI: -1.33 to 0.58). The latter could not be explained by prepregnancy body mass index, smoking, or alcohol consumption during pregnancy. The absence of a midpregnancy fall also tended to be related to the development of preeclampsia, especially among women with a low educational level (OR: 3.8; 95% CI: 0.80 to 18.19). The absence of a midpregnancy fall in diastolic blood pressure in women with a low education level may be a sign of endothelial dysfunction that is manifested during pregnancy. This might partly explain these women's susceptibility to preeclampsia.