It is safe to have sex after ovulation and avoid pregnancy?

No: Having intercourse after ovulation is not a reliable way to avoid pregnancy. Its difficult to know when ovulation occurs and the egg persists for a variable length of time after ovulation. Some couples use the "Rythem Method" to avoid pregnancy This requires avoiding intercourse during the fertile window when its most likely to get pregnant. It takes diligence and research to get it right.

Never safe: You are taking a risk to get pregnant any time you have unprotected intercourse. There are too many factors impacting a woman's menstrual cycle and when she ovulates that having unprotected intercourse always means taking a risk.