Early Growth The First Trimester Is a Very Critical Time

In the formation of the human organism, egg and sperm first unite, producing the zygote. From this point, the reproductive process occurs very rapidly:

·    Within 30 hours zygote divides in half to form 2 cells.

·    Within 4 days cell number climbs from 64 to 128 cells.

·    At 14 days the group of cells is called an embryo.

·    Within 35 days heart is beating, embryo is ¹/₃₀ of an inch (8 millimeters) long, eye and limb buds are clearly visible.

·    At 8 weeks the embryo is known as a fetus.

·    At 13 weeks (end of first trimester most organs are formed, and the fetus can move.

For purposes of discussion, the duration of pregnancy normally, 37 to 41 weeks from the mother's last menstrual period is commonly divided into three periods, called trimesters. Growth begins in the first trimester with a rapid increase in cell number. This type of growth dominates embryonic and later fetal development. The newly formed cells then begin to grow larger. Further growth and development then involve mostly an increase in cell number with some increase in cell size. By the end of 13 weeks the first trimester most organs are formed and the fetus can move.

Nutritional deficiencies and other insults transmitted through the mother to the embryo or fetus for example, injuries caused by medications and other drugs, high intakes of preformed vitamin A, radiation, or trauma can alter or arrest the current phase of development. The effects may last a lifetime. The most crit­ical time for these problems to happen is during the first trimester. Most miscarriages (more correctly termed spontaneous abortions) occur at this time. Currently, about one-half or more of all pregnancies either fail to attach to the uterine wall or undergo spontaneous abortions, often so early that a woman does not even realize she was pregnant. The early spontaneous abortions usually result from a genetic defect or fa­tal error in fetal development.

A woman should avoid substances that may harm the developing fetus, especially during the first trimester. This holds true for the time when a woman is trying to be­come pregnant. As previously mentioned, she is unlikely to be aware of her pregnancy for at least a few weeks. In addition, the fetus develops so rapidly during the first trimester that if an essential nutrient is not available, the fetus may be affected even before evidence of the deficiency appears in the mother.

For this reason, the quality of one's nutritional intake is more important than quantity during the first trimester. In other words, women should consume the same amount of food, but the foods should be more nutrient dense. Although some women lose their appetite and feel nauseated during the first trimester, they should be careful to meet nutrient needs.