Productive Medicine

Pregnancy and Birth Control

Pregnancy occurs when a female gamete, called an oocyte, unites with a male gamete, called a spermatozoon, in the female oviduct. This process is termed fertilization and usually takes place in the ampulla region of the oviduct. Once the gametes are united during fertilization, the nuclei of the male and female gametes merge, resulting in the formation of an embryo. The newly formed embryo then undergoes a series of division events called cleavage as it travels down the oviduct toward the uterus. Approximately 5 to 6 days following fertilization, the embryo enters the uterine cavity and begins to embed itself into the endometrial lining of the uterus. During normal pregnancy, the implanted embryo will continue to develop inside the uterus for an average of 38 to 40 weeks. Some pregnancies will involve the development of more than one embryo, as is the case for twins or triplets. In the developed world, most women will be monitored by an obstetrician or midwife during their pregnancy. The use of birth control or contraceptive methods decreases the probability of pregnancy. Many forms of contraceptives are currently available; some of the better known are sterilization, oral contraception, intrauterine devices, diaphragms, and condoms. The most drastic, yet most effective, form of birth control is sterilization. Sterilization involves a surgical procedure, either vasectomy in males or tubal ligation in females, which renders an individual permanently incapable of reproduction. Sterilization is generally considered by couples that do not want any further children. Oral contraception, also called the birth control pill, usually involves the administration of estrogen and progesterone to women for 21 days of a 28-day menstrual cycle. This method shuts down ovulation and thus prevents pregnancy. An intrauterine device (IUD) is a small piece of molded plastic or copper that is placed in the uterus by a physician. IUDs alter the environment of the uterus so that fertilization is unlikely to occur and, if it were to occur, prevents implantation from taking place. A diaphragm is a soft rubber or plastic cup with a flexible rim that fits over the cervix and physically prevents sperm from passing through from the vagina. When used in conjunction with spermicidal jelly, it generally prevents fertilization from occurring. A male condom is a thin plastic (usually latex) sheath that fits over the erect penis, trapping the ejaculate and preventing it from entering the vagina.

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