i was on them when i was PG with DS. i was on them from about 8 weeks through until about 6 weeks after DS was born. i don't recall having any side effects in the way of tiredness (other than what i'd expect from being PG) or the other end of the spectrum. i agree with kim - could be worth speaking to your pharmacist & see what they say. my doctor put it to me that there are other options, they just usually prescribe aldomet first because it's so tried & tested having been used for PG women for such a long time.