Like you, atenolol was the only med that worked for me post-partum. I was on it 1 1/2 yrs. before I got pregnant. My doctor okayed me staying on it for the first 13 wks ( I was on a very low 25mg. dosage). We then tried going w/out meds for two weeks since my bp was so good, but it started creeping up a bit. My doctor was not comfortable with atenolol in the 2nd trimester, since some studies show it restricts fetal growth. Luckily for me, the Aldomet I've been on is working. Here's an article for you that may provide you with some background info before you talk to your OB about Atenolol
I know if your doctor does okay you staying on, frequent ultrasounds are recommended to track the baby's growth (although my peri is doing that anyway, since hypertension in general can slow it). So far, having been on it in the first trimester has not seemed to effect the baby. Good luck to you!!
Evan 12-9-01 (PIH @ 29 weeks)