Umbilical Cord
Umbilical Cord
The umbilical cord joins the embryo to the placenta. It originates in the fetal portion of the placenta and is normally attached near the centre. The cord is typically 20 to 22 inches (50 to 55 cm) long and less than 1 inch (2.5 cm) in diameter at the time of delivery. Umbilical cords can vary widely in appearance. The major part of the cord is a pale white, gelatinous-mucoid substance called Wharton’s jelly (a gelatinous tissue that remains when the embryonic body stalk blends with the yolk sac within the umbilical cord). This substance prevents compression of the blood vessels and aids in insulating the vessels within the umbilical cord. The normal umbilical cord has two arteries and one vein that may give the cord a ropelike appearance. On occasion, the cord has only two vessels, one artery and one vein. This phenomenon is seen in less than 3% of deliveries. It may be associated with fetal anomalies and requires follow-up. The vein carries oxygenated blood to the fetus; the arteries carry deoxygenated blood back to the placenta. The cord has no pain receptors, so cutting at the time of delivery does not cause pain (Bernstein, 2003).
Amniotic Fluid
Amniotic fluid surrounds the fetus in utero. It begins production early in the pregnancy and is present in increasing amounts. Approximately 30 mL (1 oz) are present at 10 to 12 weeks gestation. The peak volume is noted around 34 weeks gestation at approximately 800 to 1000 mL. The amniotic fluid has several important functions for the fetus. It acts as a cushion against mechanical injury; helps regulate fetal temperature; allows the developing embryo or fetus room for growth, which promotes musculoskeletal development; and provides for fetal lung development. The fluid is clear yellow with a slightly alkaline pH. Amniotic fluid contains albumin, urea, uric acid, creatinine, bilirubin, lecithin (phospholipids for fat metabolism), sphingomyelin (a compound of lipids and sphingosine, found in high concentrations in the brain and other tissues of the nervous system), fructose, fat, leukocytes, proteins, epithelial cells, enzymes, and strands of lanugo (downy, fine hair found on the fetus from 20 weeks gestation until birth). Amniocentesis (discussed subsequently) can be done after the first trimester of pregnancy to aid in the determination of fetal development, maturity, health, and gender (U.S. National Library of Medicine, 2011).
Assessment of Fetal Well-Being
A variety of technological and assessment tools can be used in the evaluation of fetal well-being. These tools are used to evaluate maternal and fetal health problems, fetal congenital anomalies, and fetal growth and maturity (Table 25-2).
