Yes. Methyldopa has been the drug of choice for treatment of hypertension during pregnancy since the 1970s or earlier. So the short answer to your question is that Methyldopa has probably been used with success more times and for a longer time period with fewer side effects than any other drug used to treat hypertension during pregnancy.
Yes. Methyl dopa is a safe blood presuure medication, and has been used for many years. There are newer medication that can be used alone or in combination with methyl dopa.