Is It Advisable To Take Double Dosage Of Althea Pills Post Unprotected Sex?

Hello and Good Day,

We had unprotective sex last night for the first time since my wife had her period last january 11 (today is january 20) but she has not taken the althea pills yet. We already have 3 kids youngest is 1 and we cannot afford yet to have a new member of the family. We are planning that she has to take 2 althea pills tonight 24 hours after we had sex. Would it be ok or still guarantee?

Thank you very much.