The Chronic Hypertension and Pregnancy (CHAP) project is a large pragmatic multi-center randomized clinical trial designed to evaluate the comparative effectiveness and safety of pharmacologic treatment of mild chronic hypertension (CHTN) in pregnancy. During pregnancy, CHTN is the most common major medical disorder, most often mild (BP <160/110 mmHg), and is associated with a 3-5 fold increase in adverse outcomes including preeclampsia, perinatal death, preterm birth (PTB) and small for gestational age (SGA) infants (birth weight <10th percentile). Whereas antihypertensive therapy is a public health priority for the general population, authorities, including the American College of Obstetricians and Gynecologists (ACOG), recommend against BP lowering therapy during pregnancy unless hypertension is severe, i.e., e160/110 mm Hg, because of uncertain benefits and the concern that therapy may actually increase the risk of SGA. Based on supportive preliminary data presented herein, we hypothesize that antihypertensive therapy for CHTN during pregnancy to the goal <140/90 mmHg as currently recommended for the non-pregnant hypertensive population, will reduce the risk of several adverse pregnancy outcomes including SGA. During a 6-year project period, our consortium of 12 academic perinatal centers (25 sites), will identify 4700 women with mild CHTN and standardized BP<155/100 mmHg (which providers are more comfortable not treating) in early pregnancy and randomize them to either antihypertensive therapy (using labetalol) or to management according to ACOG recommendations (antihypertensive therapy for more severe CHTN). The women will be followed-up until discharge from the hospital after delivery and up to 3 months postpartum (long-term follow-up, including an interim 6-month phone call, is anticipated as a separate related project). The following Specific Aims will be addressed: 1.1 Primary Aim: To determine if pharmacologic treatment of mild CHTN in pregnancy to a standardized BP goal<140/90 mmHg, compared with standard management (per ACOG: no treatment unless hypertension is severe), reduces the risk of adverse pregnancy outcomes including: 1) a severe perinatal composite outcome (perinatal death, severe preeclampsia, placental abruption or indicated PTB <35 weeks) and 2) SGA. 1.2 Secondary Aims: i. To better quantify the incidence during pregnancy of rare maternal cardiovascular risks associated with mild CHTN (including death, myocardial infarction, stroke, renal failure) and examine the effect of treatment. ii. To investigate the optial gestational age to deliver women with CHTN in order to minimize maternal and perinatal complications. iii. To collect and store biospecimens including maternal blood, cord blood and placenta biopsy for future biological and biophysical studies to understand the effects of antihypertensive therapy during pregnancy. iv. To evaluate whether antihypertensive treatment during pregnancy increases post-pregnancy treatment adherence. This application summarizes the trial of the companion application and describes the operations of the DCC to provide full service electronic data capture, reporting and data management services. The extent of these data management services include: database specification, edit check programming, data management plan development and maintenance, ongoing manual data review and query management, medical coding and data cleaning and locking. Specific monitoring of observed blood pressures and blood pressure control along with safety monitoring will be a major endeavor. In addition, the DCC will provide statistical analysis (considering the pragmatic design) and reports which include the data summaries, tables, and statistical analyses for the DSMB.