Prenatal development
The process of growth and development within the womb, in which a single-cell zygote (the cell formed by the combination of a sperm and an egg) becomes an embryo, a fetus, and then a baby. The first two weeks of development are concerned with simple cell multiplication. This tiny mass of cells then adheres to the inside wall of the uterus. The next three weeks see intense cell differentiation, as the cell mass divides into separate primitive systems. At the end of eight weeks, the embryo has taken on a roughly human shape, and is called a fetus. For the next twenty weeks the fetus’ primitive circulatory, nervous, pulmonary, and other systems become more mature, and it begins to move its limbs. At 28 weeks, fat begins to accumulate under the skin, toenails and fingernails appear, and downy hair sprouts on the body and scalp. The fetus may open its eyes periodically. For the remaining weeks of development, the fetus continues to gain weight, and its internal systems reach full development.
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- Prenatal diagnosis
Diagnosis before birth. Methods for prenatal diagnosis include ultrasound of the uterus, placenta, and/or developing fetus; chorionic villus sampling (CVS) to obtain tissue for chromosome or biochemical analysis; and amniocentesis to obtain amniotic fluid for the analysis of chromosomes, enzymes, or DNA. A growing number of birth defects and diseases can be diagnosed prenatally and […]
- Prenatal radiation exposure
The exposure of an unborn baby to radiation. Radiation exposure of the fetus can occur when the mother’s abdomen is exposed to radiation from outside her body as, for example, by diagnostic X-rays. A pregnant woman may also be exposed to radiation by swallowing or breathing in radioactive materials. From the mother, radioactive materials may […]
- Prenatal surgery
The surgical treatment of the fetus before birth. Also called antenatal surgery or, most often, fetal surgery. Fetal surgery is done when the fetus is not expected to live long enough to make it through to delivery or to live long after birth unless fetal surgery is performed. For instance, if a fetus has a […]
- Preop
Short for preoperative; before a surgical operation. The opposite of preop is postop.
- Preoperative
Before surgery. As opposed to postoperative, after surgery.