Contraception Pregnancy

In order to prevent an unwanted pregnancy, it’s important to know exactly when you can get pregnant and how it can happen.Pregnancy involves three basic steps: ovulation, fertilization, and implantation.


During ovulation, a woman’s ovaries release a mature egg or eggs. The egg travels down the fallopian tube towards the uterus where it will remain, awaiting fertilization. A woman is most fertile 7 days before ovulation and up to 2 days afterwards. Nevertheless, a woman may get pregnant any day of her menstrual cycle.


The egg will remain in position for about 72 hours, but can only be fertilized within the first 12 to 24 hours. During vaginal intercourse, a man will ejaculate about 1.5 to 5 milliliters of semen, containing approximately 20 to 150 million sperm per milliliter. This may sound like a lot, but the journey to the egg is an arduous one, and only about one percent of sperm actually make it. Of those that do, usually only one fertilizes the egg.

How Pregnancy Occurs - Contraception


Once fertilized, the egg travels the remaining length of the fallopian tube and arrives in the uterus three to four days later. Implantation occurs if the embryo attaches to the uterine lining. This is a critical step in the pregnancy. As many as 50 percent of fertilized eggs are flushed out of the body (during menstruation) before implantation can occur.

Ways You Can Get Pregnant

Vaginal intercourse is by far the most common way to get pregnant. A woman may also become pregnant whenever semen comes in contact with the vagina. For this reason, withdrawal and outercourse are not particularly effective means of birth control.

There are two alternate ways to become pregnant:

  • During alternative insemination, sperm are placed into the woman’s uterus using a syringe.

  • In vitro fertilization is a process by which eggs are removed from the woman’s body, joined with sperm, and placed back in her body.

Preventing Pregnancy

Each of the five types of contraception can prevent pregnancy in a different way:

  • Behavioral methods are natural sexual practices that prevent the union of egg and sperm.
  • Barrier methods involve a physical or substance barrier that prevents sperm from entering the uterus.
  • Emergency contraception is speculated to prevent the release of eggs and/or make implantation more difficult.
  • Hormonal methods manipulate the hormones associated with reproduction (estrogen and progesterone). This prevents the release of eggs.
  • Male sterilization interrupts the vas deferens so the sperm cannot enter the seminal fluid. Female sterilization blocks the female fallopian tubes so the sperm cannot reach the egg.

Recognizing the Signs of Pregnancy

Every sexually active woman is likely to have a few pregnancy “scares” in her lifetime. Knowing pregnancy symptoms can help you determine if a scare is real.

One of the most obvious signs of pregnancy is a missed period. By this time, a pregnancy test can fairly accurately determine whether or not you are pregnant.

Other early pregnancy symptoms may include:

  • Fatigue
  • Feeling bloated
  • Mood swings
  • Nausea
  • Tender breasts
  • The urge to urinate more frequently than normal.

You may not experience all of these pregnancy symptoms. However, if you experience one or more of them, it could indicate you are pregnant. See your doctor if you have any questions or problems related to your pregnancy or your health.


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Planned Parenthood Staff. (n.d.). How pregnancy happens. Retrieved February 6, 2010, from the Planned Parenthood Web site: