Pregnancy is the transition from embryo to fetus after an egg is fertilized in order to create offspring. Gestation can be single or multiple as we recognize in twins, triplets, etc. A normal pregnancy will generally run for 38 weeks, in the first 8 weeks after fertilization the offspring is called an embryo and subsequently it is known as the fetus. There are 3 stages in a human pregnancy and extensive studies have been carried out to better understand the development of the embryo and the fetus.
The first 12 weeks of the pregnancy is known as the first trimester and is the stage that entails the highest risk of miscarriage. This stage begins with the implantation of the embryo in the uterine wall connected by the placenta. This placenta allows gases to be exchanged, nutrients to travel and waste to be removed. In this trimester there is a lot of growth and changes in the embryo.
Three quarters of all pregnant women experience some form of morning sickness during this stage which tapers off as they approach the second trimester. The nausea can occur at any time of the day, but is known as morning sickness because more often than not it occurs in the morning. After fertilization and implantation the placenta begins to grow and tests can now detect the pregnancy.
During this trimester organs are formed and the embryo consists of three layers. The first layer will become the skin, central and peripheral nervous system, eyes, ear and connective tissue. The middle layer will form the heart, the start of the circulatory system, bones, muscle and kidneys. Finally the third layer will develop into the lungs, intestine and bladder.
In the sixth week the features of the face start to develop and the following week the brain, face and limbs develop. From the eighth week when the embryo starts to move till the end of the trimester the toes, neck and sexual organs develop.
The period from the 13th to the 28th week is termed the second trimester and the risk of miscarriage is greatly reduced. Morning sickness is mostly gone, the woman has a lot of energy, eats well and starts to put on weight. Movement also termed “quickening” occurs anywhere between the 19th and 21st week but in some rare cases it can occur later. The fetus can clearly be distinguished as either male or female and in addition to urinating it can also produce insulin.
From the 29th week until delivery is termed the third trimester and the largest amount of weight gain occurs in this period and the belly that was upright in the second trimester begins to descend. The movement of the fetus can be strong enough to disrupt the woman’s activities. The pressure of the fetus often results in backache and frequent urination for the woman. The large size of the stomach causes the navel to protrude and the woman can also feel the fetus doing “acrobats”. In the later part of this trimester the fetus descends into the pelvic cavity and this is known as head engagement. The result is an ease in breathing but this added pressure gives the feeling that the bladder is always full. At this stage any baby born prematurely has a good chance of survival even if they are not full term.
Pregnancy can be an enjoyable time for the mother to be especially if she follows a healthy diet and exercises. It is a time for her to bond both with her partner as well as her baby. But it is important to take note that as a result of hormonal changes the pregnant woman is prone to mood swings and a knowledgeable partner will adjust to this and understand it is just a phase. Available out there today are many resources on how to stay healthy during this period and the joy of pregnancy.
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