Pregnancy

Historical Background

People have developed theories and speculated on pregnancy for millennia, and continue to do so. Research into birth control indicates humans have known for centuries, if not specifically, that sexual intercourse between a man and a woman could lead to pregnancy. Cultures continue to propagate beliefs about how or when pregnancy can occur, including that virgin females cannot become pregnant when having sex the first time, women control the gender, and features of the child are based upon the women's dreams or what they see when having sex, and [Page 1017]women can only become pregnant after midnight and before 5:00 a.m. These and other beliefs remain central to many peoples' ideologies regarding pregnancy. Since the early 20th century, medical science has continued to alter its understanding of pregnancy. The knowledge of the importance of sanitation during delivery has done a great deal to significantly lower the maternal mortality rate across the globe, even as many midwives in the late 19th and early 20th century, for which records are maintained, had better rates than most of their medical professional peers.

Core Definition

Pregnancy occurs when a fertilized egg—a zygote—implants itself in a woman's uterus. Implantation remains at the core of this definition. During their own gestational period, a female fetus develop her lifetime supply of eggs, and this number, by some calculations nearing 7 million, begins to drop off to about 1 million when the baby is born. Around 12 years of age, girls begin their first menstrual cycle, during which the ovary releases an egg about every 28 days. If the egg receives a sperm, pregnancy may occur. If the egg is not fertilized, the developing endometrium, or uterine lining, is shed through the vagina and urethra, known as menstruation. If uninterrupted by birth control methods after menarche, a woman's ovaries will continue to release these developed eggs throughout her lifetime until menopause, when the ovary no longer has eggs to release.

Fertilization most often occurs through vaginal intercourse between a woman and a man. Biologically, fertilization may lead to pregnancy through a complex process. Women and men may also prevent pregnancy through a variety of physical, pharmaceutical, and herbal means. If no birth control methods are used—and sometimes regardless of these methods—and intercourse occurs around 48 hours before or after the ovary releases an egg, individual sperm that travel through the vagina, uterus, and uterine tube can meet the egg and fertilize it. Propelled both by the tail and follicles and minor contractions in the uterine tube, the sperm meet the egg, but the egg only accepts one. If fertilization occurs, the zygote moves through the uterine tube into the uterus, where it implants itself in the uterine wall and remains for

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