Uncomplicated hypertension usually isn't treated during pregnancy unless systolic blood pressure is over 160 or diastolic is over 100. Some anti-hypertensives are safer than others during pregnancy...
Labetalol is a good first-line option, either orally or IV. It is both an alpha- and beta-blocker, so it doesn't decrease fetal blood flow and doesn't seem to cause growth restriction or stillbirths. And the dose can be pushed quite high, up to 2400 mg orally if needed. Save other beta-blockers for second-line. They seem to cause more problems with low birth weight, slow heart rate, or hypoglycemia in the newborn. Extended-release nifedipine is another good option for oral treatment. It isn't associated with significant adverse outcomes in newborns and infants. Methyldopa is still used sometimes because of its long history of safety during pregnancy. But it's a weak anti-hypertensive and causes more side effects than the others. Consider it as an option for women who can't use labetalol or nifedipine. Hydralazine is falling out of favor. It causes increased heart rate and other problems in the fetus and headache, palpitations, and other side effects in the mother.
Many experts advise stopping diuretics during pregnancy due to concerns about reduced plasma volume and possible preterm labor. Avoid ACE inhibitors, ARBs during pregnancy, these drugs may cause fetal injury or death.
REFERENCES
Brown C, and Garovic V, 'Drug Treatment of Hypertension in Pregnancy' (NCBI, 2015). Available at: https://www.ncbi.nlm.nih.gov/pmc/articles/PMC4558097
Treating Hypertension in Pregnancy (Medscape, 2020). Available at: https://www.medscape.com/viewarticle/406535_6