Talk to Gynecologist on BP In Pregnancy

Respected Doctors

My wife blood pressure is not controlling in Pregnancy, it's her 35 week and her BP is 140/100. As per recommendations of her gynaecologist she is using Labetalol 100 mg (2 dose per day) but the said medicine is controlling her bp only for 3 hours and then go back to 140/100. She can't use more than 2 doses of the mentioned above Medicines as per her doctor advise. What to do in this situation? Should she switch to another medicines (aldomat 250 mg)...? thanks