Making Love
Coitus is the basic reproductive method of humans. During ejaculation, which normally accompanies male orgasm, a series of muscular contractions delivers semen containing male gametes known as sperm cells or spermatozoa into the vault of the vagina. The subsequent route of the sperm from the vault of the vagina, is through the cervix and into the uterus, and then into the fallopian tubes. Millions of sperm are present in each ejaculation, to increase the chances of one fertilizing an egg or ovum. When a fertile ovum from the female is present in the fallopian tubes, the male gamete joins with the ovum resulting in fertilization and the formation of a new embryo. When a fertilized ovum reaches the uterus, it becomes implanted in the lining of the uterus, known as endometrium and a pregnancy begins.
Heterosexual intercourse (coitus), where both participants are believed to be fertile, should always be considered likely to result in pregnancy, unless adequate contraceptive (birth control) measures are taken. However, no birth control measure is 100 percent effective, with the exception of complete abstinence from heterosexual intercourse.
A prophylactic such as a condom is among the most effective methods of birth control short of sterilization or abstinence, with the World Health Organization stating that with "typical" condom use (in which condoms were sometimes incorrectly or inconsistently used), they have a failure rate of only 10-14% (with "ideal" use, they are 97% effective).[1] Surgical sterilization (tubal ligation for women or vasectomy for men) is considered permanent birth control, though it can sometimes be reversed surgically, or, rarely, the body can repair itself. Outercourse, and other sexual contact (such as mutual masturbation or oral sex), in which there is sexual activity without penis insertion, can be performed without resulting in pregnancy provided that semen does not come in contact with the vulva.