Delayed period. For delayed period?

My wife has regular period with 30 days cycle. Her period delayed for 41 days. She took a blood test on 35 day. It was around 1.2. She had cough & cold with slight fever. We thought her period could have been delayed due to these. It has been 41 days so far. She has dry cough however has not got her period yet. Few of our Frd's advised us to wait for another week & take pregnancy test. Should the delay in period due to server cough. Cold is mild . Fever is not there since last week. Her last period was on 2nd Sep, we had last unprotected sex between 23rd to 26 Sep. last two years her period had alws been regular she gets the period between 29th day or max 33 days. My question is , what could be the reason for delayed period? Can she go ahead and take treatment for her could and cough if there won't be a chance for pregnancy