How to calculate the day of ovulation effective contraception?

Question
Hello doctor,
If I have sex before 5 days of ovulation, is there any chance of pregnancy? I had sex on 8/3 and ovulated on 3/13! How to calculate the date of ovulation is effective contraception?
Anonymous customer
Answer
Answered by Specialist I Nguyen Thi Kim Dung - Obstetrician and Gynecologist - Obstetrics Department - Vinmec Times City International Hospital
Hello,
To the question " How to calculate the day of ovulation effective contraception? ", the doctor would like to answer as follows:
The method of contraception by calculating the day of ovulation is not effective at preventing pregnancy, especially for women with irregular menstrual periods. According to theory, having sex 3 days before and 1 day after ovulation, the chances of conception are high. Or for women with a regular 28-day menstrual cycle, the safe time to have sex is from the 10th to 17th day of the menstrual cycle. However, around the remaining days the possibility of conception is still there although lower, it is important to determine the correct day of ovulation. You can go to a gynecologist for advice on suitable birth control methods.
Contraceptives that are more than 99% effective:
Contraceptive implants (lasts up to 3 years) Hormonal IUDs (up to 5 years) IUDs, or non-contained IUDs endocrine (up to 5 to 10 years) Female sterilization (permanent) Male sterilization or vasectomy (permanent) Vinmec Health System for further examination and consultation. Thank you for trusting and sending questions to Vinmec. Wishing you lots of health.
Best regards!