Conception FAQs from UPMC in Central Pa.

Inside your ovaries each month, a group of eggs begins to grow in small, fluid-filled sacs called follicles. Ovulation occurs when one of the eggs erupts from the follicle, usually about two weeks before your period starts. After the egg leaves the follicle, your body releases a hormone that helps thicken the lining of your uterus to prepare it for the egg. The egg moves through the fallopian tube, where conception takes place. The egg stays in the fallopian tube for about 24 hours waiting for fertilization by a single sperm.

After you ovulate, your egg stays in the fallopian tube for 12 to 24 hours waiting to be fertilized by one of the 250 million sperm (on average) that your partner ejaculates during sex. When your partner ejaculates, his sperm travel from your vagina through your cervix and into your uterus to the fertilized egg in your fallopian tube. Only about 400 sperm will survive the 10-hour journey to the egg and only one will succeed in burrowing through its outer membrane.

For fertilization to occur, sperm must reach the egg within a specific timeframe. Sperm can survive for up to 72 hours after ejaculation, but the egg can survive for no more than 24 hours after ovulation. If sperm reach the fallopian tube too early, they risk dying before the egg shows up. If sperm reach the fallopian tube too late, the egg will be gone. Additionally, the egg is present in only one of your two fallopian tubes in a given month.

Before fertilization, hundreds of sperm will surround your egg while trying to reach the egg's nucleus. Only one sperm will succeed in penetrating the egg's outer membrane. After the sperm penetrates the egg, the egg immediately undergoes a chemical reaction that prevents other sperm from penetrating. Chromosomes carried by the sperm and the egg then come together, and the egg is officially fertilized. About a week later, a ball of around 100 cells (called a blastocyst) reaches your uterus and implants into the uterine lining.

When it comes to conceiving a baby, timing is everything. To boost your odds, aim to have sex sometime between 72 hours before and 24 hours after you ovulate.

The best thing you can do to prepare for conception is to get your body in the best possible shape for making a baby. You should stop drinking alcohol, smoking and taking drugs, even over-the-counter medications. You should inform your physician of your plans to conceive and ask him or her if you should continue taking prescription medications. Up to three months before you plan to try to conceive, you should begin taking a multivitamin that contains at least 400 micrograms of folic acid to reduce your baby's risk of birth defects.

HCG, the pregnancy hormone, is present in your blood right after conception. However, pregnancy tests are unable to detect HCG in your urine until after the egg attaches to the uterus during implantation. At the earliest, an over-the-counter pregnancy test will not be positive until nine to 10 days after ovulation. Most women do not experience early pregnancy symptoms until after implantation, but some notice symptoms sooner.