There was very little evidence available on treatment initiation thresholds for chronic hypertension in pregnancy, so the committee based their recommendations on the values specified in the recent Control of Hypertension in Pregnancy Study (CHIPS) and the NICE guideline on hypertension in adults. There was evidence for target blood pressure levels from the large CHIPS trial, so the committee made recommendations based on this. There was some very limited evidence of both benefits and harms for different antihypertensive medicines. However, there was not enough evidence to recommend one treatment over another. As labetalol, nifedipine and methyldopa had been recommended in the previous guideline (for gestational hypertension and pre-eclampsia), and these medicines had been used for many years in pregnancy, the committee agreed they should be preferred treatment options for chronic hypertension in pregnancy. Labetalol is specifically licensed for use in pregnancy and so is suggested as the first-line option, with nifedipine as the next alternative, and methyldopa as the third option (as it may lead to more side effects and be the least effective option of the 3). There was some very limited evidence for the benefits of aspirin in reducing preterm births and neonatal unit admissions, so the committee retained the recommendation on aspirin from the previous guideline, but incorporated it into the section on the treatment of chronic hypertension in pregnancy. The committee noted that the studies used different doses of aspirin (ranging from 50 150 mg daily), and that common practice in the UK was to offer 75 150 mg, therefore this dose range was recommended. The committee were aware of the link between chronic hypertension and both pre-existing and gestational diabetes, therefore they made an overarching recommendation at the beginning of the guideline to cross-refer to the existing NICE guideline on diabetes in pregnancy. 