From the Research
The probability of pregnancy from ejaculation 4 days before ovulation is approximately 10%. Sperm can survive in the female reproductive tract for up to 5 days, making pregnancy possible even from intercourse several days before ovulation. The highest pregnancy chances occur from intercourse on the day of ovulation or the two days prior, with rates of about 25-30% 1. Four days before ovulation represents lower but still significant risk.
Factors Influencing Pregnancy Risk
- The timing of sexual intercourse in relation to ovulation strongly influences the chance of conception 1.
- The probability of conception ranges from 0.10 when intercourse occurs five days before ovulation to 0.33 when it occurs on the day of ovulation itself 1.
- Emergency contraception like levonorgestrel (Plan B) can be effective if taken within 72 hours of unprotected intercourse, with ulipristal acetate (ella) effective up to 5 days after 2, 3.
Recommendations for Pregnancy Prevention
- For future prevention, consider consistent use of contraceptive methods like condoms, hormonal birth control, or IUDs.
- Ulipristal acetate is the dominant choice of oral emergency contraception among combined oral contraceptive users, especially in cases of obesity or potential interactions with other contraceptives 4.
- Fertility varies between individuals based on age, health status, and other factors, so these probabilities represent population averages rather than precise individual predictions.
Key Considerations
- The copper intrauterine device (IUD) is the most effective method of emergency contraception and provides ongoing contraception for up to 10 years 2, 3.
- Women who weigh more than 75 kg or have a body mass index greater than 25 kg/m(2) may have a higher risk of unintended pregnancy when using oral levonorgestrel emergency contraception, making ulipristal acetate or copper IUDs preferable in this setting 2, 5.