When Exactly Does Conception Occur: Intercourse, Ovulation, and Implantation

Many people are unsure of exactly when conception occurs, especially if intercourse and ovulation are on separate days. There are many things that come into play leading up to conception.

 Fertility, Ovulation, and the Menstrual Cycle

The body begins preparing for ovulation on the day one of the menstrual cycle. During this time, the ovaries start preparing a few follicles to be the potential egg. After your bleeding period is over, your body starts producing estrogen, and the ovaries are being primed for ovulation. This is when the cervical fluid becomes more “fertile.”

If the cervical fluid becomes fertile up to five days prior to ovulation and you have sexual intercourse, the sperm can live inside your fallopian tube during this time. For example, you can have intercourse on Monday and not ovulate until Friday but still conceive. The chances of conceiving a girl are greater this way because female sperm tend to live longer than male sperm.

While sperm can live up to five days inside a woman's body, the egg only lives 12 to 24 hours. Rarely, a second egg will pop out 24 hours after the first.

Conception – When and How it Happens

There is about a week-long window for conception to occur, but it will only occur under specific conditions. In order for sperm to live longer than about 48 hours, there has to be good, fertile cervical fluid present. In order for the egg to be fertilized, there needs to be sperm present, or intercourse must occur within the first 12 hours of ovulation. With these circumstances in mind, it's important to know when ovulation does occur through fertility charting.

The sperm and egg combine within 24 hours after ovulation. The body will not know it's pregnant until the fertilized egg implants into the uterine wall, some 5 to 12 days after ovulation. Either of these points can be seen as the moment of conception. When the fertilized egg implants, it starts sending signals to the corpus luteum to continue producing progesterone. This is when minute levels of hCG, the pregnancy hormone, are released.

During a healthy pregnancy, hCG levels will double every other day. The earliest a pregnancy test would show a positive would be on day 7 post ovulation, but this happens rarely. Even with the most sensitive tests, you have a better chance of seeing a positive at around 10 days post ovulation.