Pregnancy is usually divided in three trimesters, each lasting 12 to 13 weeks…
A normal pregnancy lasts 40 weeks counting from two weeks before conception occurs, or the first day of the last menstrual period. Pregnancy is usually divided in three trimesters, each lasting 12 to 13 weeks.
Pregnancy starts around two weeks after a woman has her period. The egg is fertilized in the fallopian tube 12 to 24 hours after it is released from the ovary. After conception, the egg is now called a zygote, starts successive cellular divisions and moves into the uterus where it attaches to the uterine wall.
In the early stages of pregnancy, women experience many symptoms that are mostly related to the hormonal changes typical of pregnancy. The placenta cells start producing hCG from the moment of implantation and progesterone rises, causing nausea and tiredness among other symptoms. The body has to do a major adjustment to accommodate the changes that have to take place, in order for the embryo to develop. These hormones affect almost every organ system in your body. For example the heart will start working harder to adjust to the increase in the volume of blood that supplies the growing embryo. This is the period where most miscarriages happen, usually due to defects in the development of the embryo .
During the first month of pregnancy, despite the woman’s body not changing in appearance, there are a lot of development processes taking place in the embryo. At the beginning of the month, the embryo is the size of a poppy-seed and composed of three distinct cellular layers that will develop the different organ systems. There is also the formation of the umbilical cord, that delivers nutrients to the embryo, and the yolk sac, that produces red blood cells. At the seventh week, the heart, brain and limbs start to form. After one month, the embryo is about the size of a pea .
By the end of the second month, the embryo is about the size of a kidney bean and has formed wrists, ankles, fingers and eyelids. At this stage, your baby’s heart beats and sex organs begin to form. After the eighth week, the baby is called a fetus and has most of the organs formed.
In the third month the intestine begins to develop and the fetus’ bones, nerves and muscles start to work. The fetus is about 5.4 centimeters long by the end of this month and has increasingly more complex features, as the eyes and ears go into position, and internal organs start functioning, kidneys produce urine and liver produces bile.
In the second trimester, the symptoms that you experienced so far subside, as your body gets accustomed to the hormonal changes. Instead you will start experiencing other things; you will have a baby bump, gain more weight and have back pain. Also, there is increased fluid retention that causes swollen feet and ankles and sometimes carpel tunnel syndrome. At this stage you have a lower risk of miscarriage. It is normal to feel slight pain when you shift position due to round ligament stretching, the ligament that supports your uterus.
By the fourth month of pregnancy there is the development of skin, eyelashes, eyebrows, fingernails and neck. The fetus can now move the limbs, hear and swallow. If it is a girl the ovaries develop eggs. The baby is now 10 centimeters long and weighs around 100 grams.
In the fifth month, you will start to feel the baby’s movements and an ultrasound can now reveal the sex of the baby. The fetus is covered in fine hairs (lanugo) and has a wax like substance (vernix caseosa) protecting the skin from the amniotic fluid. At this stage other important development takes place, the bone marrow starts to make the blood cells that will give rise to your baby’s immune system. The baby is now 26cm long and steadily gains weight.
At 6 months the baby is fully formed, the hair begins to grow, the eyes open, and the baby starts being more active inside the uterus. If you are having a boy, the testes will descend into the scrotum. At this stage the baby measures about 28 to 35 centimeters and weights around 500 to 750 grams.
The discomfort that you experience during the second trimester usually gets worse during the third trimester. As your belly grows the uterus expands upwards and compresses the stomach and the diaphragm, causing gastrointestinal disturbances and shortness of breath, respectively. There is an increase in fluid retention that can lead to swelling of hands, ankles and feet. The weight of the expanded uterus leads to the compression of the bladder and to back pain. It is normal to experience leakage of colostrum from the breasts as the tissue prepares for breastfeeding .
At the seventh month of pregnancy the baby can respond to touch, sounds and light, as the senses become more sophisticated. You can sense that there are regular sleeping cycles. The lungs are formed and preform training breathing movements. The baby weights now 1 kg and measures around 39 centimeters.
In the eighth month the fetus puts on weight, at a rate of about 200 grams per week, in the form of fat tissue, and the bones become more solid. The weight gain begins to smooth out the wrinkled skin. The baby now weights around 2 kg and measures 44 centimeters.
During the ninth month the fetus gets ready for birth having fully developed lungs and by turning the head towards the cervix. The baby is now completely formed, weights 3 kg and measures 50 centimeters in average.
Just remember that all pregnancies are different and the development of the baby and the symptoms experienced are highly variable. So do not worry if you do not feel exactly as described at each stage. If you feel pain, bleeding or dizziness you should contact your doctor, so always be alert to your body and get to know the normal symptoms of pregnancy.