Skip to main content

pregnancy

pregnancy, period of time between fertilization of the ovum (conception) and birth, during which mammals carry their developing young in the uterus (see embryo). The average duration of pregnancy in humans is about 280 days, equal to 9 calendar months. After the fertilized ovum is implanted in the uterus, rapid changes occur in the reproductive organs of the mother. The uterus becomes larger and more flexible, enlargement of the breasts begins, and alteration of renal function, blood volume, and blood cell count occur. Movement of the fetus and fetal heartbeat can be detected early in pregnancy.

One test that has been used to determine pregnancy uses blood or urine samples to detect a hormone known as BhCG, found exclusively in pregnant women. Later, prenatal diagnostic tests such as alpha fetoprotein, amniocentesis, and chorionic villus sampling may be performed as screening measures for congenital defects. Ultrasound, a sonar device using high-frequency wavelengths, is used to detect defects, measure fetal heartbeat, and monitor growth of a fetus.

Complications of pregnancy include eclampsia, premature birth, and erythroblastosis fetalis (Rh incompatibility). Ectopic pregnancy, in which the fetus begins to develop outside the uterus, often in a fallopian tube, is another complication. It is often the result of scarring from a sexually transmitted disease. Smoking has been linked to low–birth weight infants; alcohol consumption during pregnancy has been linked to a group of defects called fetal alcohol syndrome.

The technology relating to pregnancy has made great advances and has created a number of ethical issues. Many women in their 40s are now able to sustain successful pregnancies, due to technological devices that carefully monitor the progress of the fetus. In vitro fertilization and other infertility treatments have allowed even postmenopausal women to give birth. The use of fertility drugs has led to a marked increase in multiple births. Abortion, in which pregnancy is terminated prior to birth, has long been a subject of heated debate, and surrogate motherhood (see surrogate mother) has also raised ethical issues in recent years.

See also amenorrhea; birth defects; midwifery.

See J. T. Queenan and C. N. Queenan, ed. A New Life (1992); C. A. Bean, Methods of Childbirth (1990);; Boston Women's Health Book Collective, Our Bodies, Ourselves for the New Century (1998).

Cite this article
Pick a style below, and copy the text for your bibliography.

  • MLA
  • Chicago
  • APA

"pregnancy." The Columbia Encyclopedia, 6th ed.. . Encyclopedia.com. 20 Aug. 2017 <http://www.encyclopedia.com>.

"pregnancy." The Columbia Encyclopedia, 6th ed.. . Encyclopedia.com. (August 20, 2017). http://www.encyclopedia.com/reference/encyclopedias-almanacs-transcripts-and-maps/pregnancy

"pregnancy." The Columbia Encyclopedia, 6th ed.. . Retrieved August 20, 2017 from Encyclopedia.com: http://www.encyclopedia.com/reference/encyclopedias-almanacs-transcripts-and-maps/pregnancy

Learn more about citation styles

Citation styles

Encyclopedia.com gives you the ability to cite reference entries and articles according to common styles from the Modern Language Association (MLA), The Chicago Manual of Style, and the American Psychological Association (APA).

Within the “Cite this article” tool, pick a style to see how all available information looks when formatted according to that style. Then, copy and paste the text into your bibliography or works cited list.

Because each style has its own formatting nuances that evolve over time and not all information is available for every reference entry or article, Encyclopedia.com cannot guarantee each citation it generates. Therefore, it’s best to use Encyclopedia.com citations as a starting point before checking the style against your school or publication’s requirements and the most-recent information available at these sites:

Modern Language Association

http://www.mla.org/style

The Chicago Manual of Style

http://www.chicagomanualofstyle.org/tools_citationguide.html

American Psychological Association

http://apastyle.apa.org/

Notes:
  • Most online reference entries and articles do not have page numbers. Therefore, that information is unavailable for most Encyclopedia.com content. However, the date of retrieval is often important. Refer to each style’s convention regarding the best way to format page numbers and retrieval dates.
  • In addition to the MLA, Chicago, and APA styles, your school, university, publication, or institution may have its own requirements for citations. Therefore, be sure to refer to those guidelines when editing your bibliography or works cited list.