Does Atenolol have any side effect on menstrual cycle? Seems as though I've been missing my periods a lot. I've been irregular and missed periods in 2-3 week intervals before, but this has been the longest. my last cycle was feb 09. other possible culprit could be from my last diagnosis from my obgyn that i have slight endometriosis and a couple of ovarian cysts. but isn't 3 mos pretty long? and no, i coudlnt be pregnant because my hubby had a vasectomy done 4yrs ago. any insights?