Hypertensive disorders of pregnancy affect up to 10% of all pregnant women in the United States, and the most severe form, preeclampsia, is the leading cause of maternal and fetal death or morbidity. Although the mechanisms for such complications are unclear, it has been proposed that either gestational hypertension or preeclampsia is associated with a hyperadrenergic state, which may contribute to the pathophysiology of these conditions. Sympathetic adrenergic control plays an important role in blood pressure maintenance in humans. Vasomotor sympathetic activity was found to increase in normal pregnancy and to be even greater in women with gestational hypertension or preeclampsia in late pregnancy. However, it is unknown whether sympathetic hyperactivity develops early in normal pregnancy, remaining high throughout the entire gestation, or whether this sympathetic activation only occurs at term, providing the substrate for gestational hypertension or preeclampsia. We found in 11 healthy Caucasian women (24-35 years old) that during early pregnancy (within 8 weeks of gestation), supine resting muscle sympathetic nerve activity (MSNA) was markedly greater (i.e., approximately twofold) compared with that of pre-pregnancy, while paradoxically their blood pressure and peripheral vascular resistance appeared to be lower. This finding is counter to the prevailing wisdom regarding the neurohormonal adaptation to normal pregnancy, which suggests that sympathetic activation occurs only in late pregnancy, and to our knowledge, there are no published nerve recordings in early human pregnancy. Supine MSNA remained elevated, while blood pressure increased slightly during late pregnancy in these women. Within 10 weeks after delivery, supine MSNA returned to the level of pre-pregnancy. One woman developed gestational hypertension at term; during early pregnancy she had greater supine blood pressure, heart rate, and MSNA when compared to other early pregnant women with normal pregnancies. These preliminary results suggest that sympathetic activation may be a universal characteristic of normal pregnancy in humans, while women with gestational hypertension and preeclampsia may have a further increase in sympathetic neural activity during early pregnancy.