Pregnancy

Description

"A normal pregnancy, from ovulation to delivery, averages 265 to 280 days, or approximately nine calendar months. It is divided into three stages, or trimesters. "

The First Trimester

"During the first trimester - the first three months - the baby is called an embryo. This is the most critical phase for the development of vital organs. Because cells are dividing rapidly and organs are forming, the baby is vulnerable to physical and environmental factors that may affect the mother. It is especially important during these months to avoid exposure to x-rays and contagious diseases and to abstain from drugs and alcohol.

During the first trimester the mother's body is creating two vital structures that ensure support and nourishment of the developing baby: the amniotic sac and the placenta.

The baby lives and grows enclosed in the amniotic sac or membrane. The baby floats free in a clear liquid called amniotic fluid, which increases from about 3 ounces at the end of the first trimester to as much as 1 1/2 quarts at term. The amniotic fluid protects the baby by providing a constant and perfect environment for growth and development. It also functions as a shock absorber so that daily activities and exercise do not bounce the baby around too much.

Extending from the wall of the uterus to the baby's umbilical cord, the placenta is the connection or bridge between mother and baby. The mother's blood vessels spiderweb into the placenta and deliver oxygen and nutrients needed for the baby's growth, while at the same time picking up carbon dioxide and waste that need to be removed and excreted.

The available supply of nutrients flows from mother to baby through the placenta.

Although the placenta is amazing, it is not flawless. It is unable, in most cases, to distinguish between needed substances and harmful substances (see Prenatal Care). It recognizes substances simply by the concentration in the mother's blood and pumps a like concentration across to the baby. This means that if the mother has a high concentration of drugs, alcohol, or nicotine in the blood (see Pregnancy and Smoking), the placenta will deliver a like concentration to the baby.

The placenta forms during the first few weeks of pregnancy and begins to function around the sixth week. It performs optimally until shortly before delivery. This aging and slowdown may be necessary to trigger delivery.

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The Second Trimester

"The middle of the pregnancy, months 4 to 6, forms the second trimester. The baby is completely formed, but a refinement of organs and body systems is still needed. Now the baby is called a fetus.

Though unable to live independently, the fetus is far more developed than the more primitive embryo. As the weight creeps up and the belly begins to bulge, many women start to worry about weight gain. But it is necessary to eat well since the baby and mother are an inseparable pair. When you skip meals and make poor food choices, so does the developing baby. This is not the time to diet or start some unusual eating regimen that may jeopardize the baby's growth.

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The Third Trimester

"In the last trimester, months 7 to 9, nutrient demands are the greatest as the baby goes through his or her final growth spurt before birth. Fetal weight triples during this trimester to an average birth weight of about seven pounds. Brain, muscles, bones, and fatty tissues are growing rapidly, and the liver, lungs, adrenal glands, and diaphragm are maturing. To meet the baby's increased demands, the absorptive capacity and transport efficiency of the placenta reach a peak in the third trimester and then slowly decline just before birth.

A woman's body undergoes many changes during the nine months of pregnancy. Heart rate increases to circulate the increased amount of blood. The lung capacity increases, and a pregnant woman actually uses 15 percent more oxygen. The renal tract dilates and holds more urine. The urge to urinate increases in early pregnancy, followed by increased thirst.

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Questions to Ask Your Doctor

"What changes in nutrition are required?

What bodily changes can be expected?

What changes in lifestyle need to be made?

How much weight can I expect to gain?

What are the possible complications?

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• Pregnancy and Childbirth
• Women's Health