Definition of Pregnancy
Pregnancy: The state of carrying a developing
embryo or fetus within the female body. This condition can
be indicated by positive results on an over-the-counter
urine test, and confirmed through a blood test, ultrasound,
detection of fetal heartbeat, or an X-ray. Pregnancy lasts
for about nine months, measured from the date of the
woman's last menstrual period (LMP). It is conventionally
divided into three trimesters, each roughly three months
long.
The most important tasks of basic fetal cell
differentiation occur during the first trimester, so any
harm done to the fetus during this period is most likely to
result in miscarriage or serious disability. There is
little to no chance that a first-trimester fetus can
survive outside the womb, even with the best hospital care.
Its systems are simply too undeveloped. This stage truly
ends with the phenomenon of quickening: the mother's first
perception of fetal movement. It is in the first trimester
that some women experience "morning sickness," a form of
nausea on awaking that usually passes within an hour. The
breasts also begin to prepare for nursing, and painful
soreness from hardening milk glands may result. As the
pregnancy progresses, the mother may experience many
physical and emotional changes, ranging from increased
moodiness to darkening of the skin in various areas. During
the second trimester, the fetus undergoes a remarkable
series of developments. Its physical parts become fully
distinct and at least somewhat operational. With the best
medical care, a second-trimester fetus born prematurely has
at least some chance of survival, although developmental
delays and other handicaps may emerge later. As the fetus
grows in size, the mother's pregnant state will begin to be
obvious. In the third trimester, the fetus enters the final
stage of preparation for birth. It increases rapidly in
weight, as does the mother. As the end of the pregnancy
nears, there may be discomfort as the fetus moves into
position in the woman's lower abdomen. Edema (swelling of
the ankles), back pain, and balance problems are sometimes
experienced during this time period. Most women are able to
go about their usual activities until the very last days or
weeks of pregnancy, including non-impact exercise and work.
During the final days, some feel too much discomfort to
continue at a full pace, although others report greatly
increased energy just before the birth. Pregnancy ends when
the birth process begins.
See also acute fatty liver of
pregnancy; ectopic pregnancy; fetal alcohol syndrome; fetal
alcohol effect; hyperemesis gravidarum; preeclampsia;
pregnancy, tubal; prenatal care; prenatal development;
birth defect; teratogen.
Last Editorial Review: 11/30/1999 8:49:00 PMCommon Misspellings: pregnacy, pregancy, pregency, pregnanacy
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