Pregnancy is a prime differentiating experienceamong all experiences for a woman during her entire lifetime. This wonderful experience is so different from any other stage in a woman’s life that it ought to be understood for what it is and what it encompasses. Simply put, following are the stages in normal pregnancy.
The ovaries are two almond-shaped glands placed one on each side of the uterus. They contain a large number of immature ova (eggs), each one of these ova begins to mature and develops into a Graffian follicle. When the follicle has matured, it secretes enough estradiol to trigger the acute release of Luteinizing Hormone (LH). In the average cycle of 28 days, this LH surge starts around Day-12 of the cycle and may last 48 hours. The release of LH matures the egg and weakens the wall of the follicle in the ovary. Tension within the follicle leads to its rupture and thus ovulation takes place. Between 14th to 18th days of menstruation cycle of the woman (Days vary depending upon the length of menstruation cycle. The 14th day is said in context with an average menstrual cycle of 28 days) an ovary releases a ripe egg. The egg is caught by the fingers of the fallopian tube and is taken inside the tube. The egg can survive inside the tube for approximately 24 hours. In some women, ovulation features a characteristic pain called Mittelschhmerz (German term meaning ‘middle pain’) which lasts for several hours.
Conception takes place by the activity of the male and female essential sex organs – the testes and the ovaries – producing the male and female sex cells, sperm and ova. When a man reaches orgasm during intercourse, the semen is ejaculated in the woman’s vagina from the male sex organ – the penis. This semen contained around 200 to 400 millions sperms. Many of them are spilled out or are lost in the way, but some swim through the mucus secreted baby the cervix. This cervix becomes thin and stretchy around ovulation and then the sperms cross the womb into the fallopian tube. The sperm can survive in the tube for 48 hours. Sperms carry a substance that can dissolve the outer layer of the egg. In this way, one of them penetrates the egg. When one sperm has entered successfully in the egg, no other sperm can get inside. The sperm loses its tail and its head begins to swell. Now the union of the two cells, the egg of the mother and the sperm of the father, forms a single cell, which later develops into the baby.
The Cell Division
With conception, the cell division starts taking place. The cell starts to divide into more and more number of cells, and travels down the fallopian tubes.
Reaching the Womb
Approximately on the fourth day after the fertilisation, the egg reaches the cavity of the womb. Till this time it develops into a ball of about 100 cells called blastocyst, with a hollow fluid-filled centre, but is still small to be seen with the naked eye. For the next few years, it floats about in the womb cavity.
The blastocyst gets embedded in the soft, thick lining of the womb at about the end of the week three. This is called implantation. When the egg is securely attached to the lining of the womb, conception is complete. Placenta is formed when sponge like fingers from the outer cells of the embryo starts to burrow into the lining, to link up with the mother’s blood vessels. Placenta is an organ to which the foetus is attached by the means of an umbilical cord. It is the lifeline of the foetus. Placenta provides nourishment to the growing foetus through the maternal blood. Some of the cells of the foetus develop into the umbilical cord, and the membranes that protect the baby. The inner cells of the foetus divide into three layers, which develop into the different body parts of the baby.
Changes in the Body
Pregnancy is the period when maximum changes takes place in the body of woman. It is also called the period of great psychological stress for the woman. The development of the foetus brings about many physiological, biochemical and hormonal changes in the body of the mother. Let us understand these changes to be able to understand pregnancy and the causes of common discomforts (which women come across in different phases of pregnancy) better and be prepared to cope up with these changes.
Increase in the Basic Metabolic Rate (BMR)
There is a pronounced increase in the BMR due to the foetal growth and development. It rises by about 5% in the first trimester and around 12% in the later stage of pregnancy.
There are marked gastrointestinal changes during pregnancy. Nausea, vomiting and constipation occur due to reduced gastric tone and secretion. The acid and pepsin secretion in the stomach is less and there is regurgitation of the stomach contents in the esophagus leading to a sensation of heartburn and vomiting. This becomes more pronounced with the increasing pressure of the foetus. In the later stages of pregnancy, the efficiency of absorption of nutrients increases as a result of natural mechanism of the adaptation to the increased needs of the body. ‘IPCA’ or craving for some particular food and aversion to others observed in pregnant ladies is also a result of gastrointestinal changes.
During pregnancy increased secretion of the growth hormone by the pituitary gland, thyroxin secreted by thyroid gland which regulates metabolism in the body, aldosterone, the salt-conserving hormone by the adrenal gland and parathormone secreted by the parathyroid gland which regulates calcium, phosphorous and magnesium are noticed.
Changes in the Body Fluid
There is an increase in the blood volume 40% by the end of the pregnancy. The capacity of the heart to pump blood is increased by 33%. The increased amount of blood is required to carry the nutrients to the foetus and take metabolic wastes away from the foetus. With the increase in the blood volume, most of the nutrients carried by the fluids are available to the placenta. Intracellular water also increases in addition to the increase in fluid with the circulatory system. With the increase in blood volume, the concentration of plasma proteins, haemoglobin and other blood constituents is lowered. This is usually a cause of anemia which is experienced by 60% to 70% of the pregnant woman.
Altered Renal Functions
There is an increased production of the various metabolites like creatinine, urea and other waste products due to foetal and maternal metabolism during pregnancy. To facilitate their clearance, the rate of blood flow through kidneys is increased with a subsequent increase in the rate of glomerular filtration in the nephrons.
Developmental Stages of Pregnancy
On the basis of various changes, complications and different stages of foetal development the human pregnancy is divided into three trimesters. Different trimesters bring about different changes and developments in the mother and in the foetus. Human pregnancy lasts approximately 9 calendar months between the time of the last menstrual cycle and childbirth (approximately 38 weeks from fertilisation).
The medical term for a pregnant woman is genetalian, just as the medical term for the potential baby is embryo (early weeks) and then foetus (until birth). A woman who is pregnant for the first time is known as a primigravida.