Does Skipped Period And Headache After Unprotected Sex Indicate Pregnancy?

Hi, may I answer your health queries right now ? Please type your query here...My wife - age 44 years complains of headache and nausea. She had her first day of period on 11th January 2011 and till date she has not got her next period. She has undergone ligation in Nov2009. We had unprotected sex aroundJanuary 29th and 30th. Please help !! Is she pregnant. She has history of irregular periods and has undergone abortions thrice