Life in the Uterus

Your baby's life support system

The development of the fetus inside the utero from a tiny group of cells to a fully grown baby occurs with the help of the placenta, umbilical cord and the amniotic fluid. This trio forms your baby's life support system before she makes her entry into the world.

The Placenta

• The placenta is a temporary, disc-shaped but an essential organ through which the fetus absorbs food and eliminates waste. It is connected to the uterine wall on one end and attached to the baby via an umbilical cord.
• There is an on-going delicate interchange between the mother and the fetus. Materials travel from the maternal system to the other and vice versa. For example excess blood sugar from the mother's blood passes into the fetal blood until equality is achieved. That is the sugar the mother eats is passed to her baby. Oppositely excess carbon dioxide from the fetal blood crosses over into the mother's blood and is exhaled by her lungs. The mother essentially breathes for her child. Likewise all waste products are absorbed and eliminated through the mother's kidneys.
• The placenta protects the fetus by blocking the passage of many potentially harmful substances e.g. drugs and chemicals
• The placenta is essentially a network of arteries and veins fully functioning between weeks 10 and 12; it collects oxygen and nutrients from the maternal bloodstream, processes them and passes them on to the baby. It also filters and transports waste materials from the fetus (carbon dioxide, baby's waste) to the mother's system for disposal. However maternal blood and baby's blood can come very close to each other but do not mix.
• The placenta is also responsible for the manufacture of a number of hormones viz HcG, HPL, Oestriol and Progesterone
• The placenta develops from the chorionic villi during the second month of pregnancy. The chorion is the outer surface of the sac holding the embryo. On one side the villi will burrow into the uterine wall to receive nourishment from the mother and the villi on the opposite end will flatten out.
• The placenta will grow in size and reach its full thickness of about 2.5 cm by the 4th month. At birth it will weigh about 500 gm and measure at 20 cm in diameter, about one sixth the size of the baby.

Amniotic Fluid - the useful fluid

• The fluid is essentially water at first; it is colorless and surrounds the fetus. As pregnancy advances, the fluid will start to turn straw-colored as it now contains skin cells shed by the fetus, fetal hair, vernix, various minerals, salt, sugar as well as fetal urine.
• Until 14 weeks amniotic fluid is absorbed by the baby's skin. As her kidneys start to function and her sucking reflex develops she will start to swallow the fluid and excrete it back into the sac as urine. Most of the fluid contained in the sac is now fetal urine.
• Amniotic fluid serves many functions. It allows the fetus to move unhampered hence aiding in the development of muscles and bones. It is particularly useful for fetal lung development
• It acts as a good insulator against cold and heat and provides the fetus protection against temperature changes. It is also and excellent shock absorber
• The fluid can also provide valuable information about fetal well being and growth.
• Pregnancy doesn't lessen the chances for injury but the fetus in most instances is cushioned by the amniotic fluid against blows and falls. An accident rarely triggers premature labor or membrane rupture. It only becomes a situation for concern if the injury involves the use of weapons or sharp penetrative objects.
• 95% of the fluid is replenished every day. During the later half of pregnancy fluid is lost because it is swallowed by the fetus. Most of it is returned as urine. About one pint is swallowed and a similar quantity is urinated on a daily basis. Baby swallows amniotic fluid as she practices breathing and then urinates it out. The fluid is constantly being recirculated.
• At 16 weeks the fluid measures at about 200 ml and at term the volume grows to about 1000 ml.

Umbilical Cord

• The cord starts to form by the 26th day of embryonic life; it is usually about 50 cm long, 1-2 cm in width with 2 arteries and 1 vein.
• It coils into a spiral. The cord is a moist dull white, semitransparent, jelly like rope that runs from the navel of the fetus to the fetal surface of the placenta. It is considered the lifeline of the fetus as it connects the fetus to the nutrient-rich placenta.
• Some cords are straight, some twisted and others become knotty because of fetal movements.
• Inside the cord is a jelly like substance called the 'Wharton's Jelly' which cushions the blood vessels. Occasionally the cord forms a knot, known as false knot but this seldom poses a problem as it doesn't hinder the blood flow.
• Fetal blood which is low in oxygen and high in waste products travels through the two arteries into the placenta. Blood gets purified; oxygen and nutrients are absorbed from the maternal blood and returns to the fetus through the single umbilical vein.