In the normal menstrual cycle in a female, the hormones such as follicle stimulating hormone (FSH), estrogen and progesterone are secreted. FSH causes actions on ovaries to produce a mature egg, whereas, estrogen and progesterone are concerned mainly with uterus, breast development and maintenance of uterus, respectively.
During ovulation, when the mature egg enters into the uterus, it stays there for some span of days after which it is expelled out of the uterus in the form of bleeding with the shredding of the uterus wall. If before the expulsion, there happens to be an available sperm inside the uterus, then fertilization takes place and a zygote is formed. And as a result of which pregnancy takes place.
3 Stages of Pregnancy
The pregnancy continues up till 36-42 weeks (9 months). These 9 months have been divided into 3 trimesters based on the growth and development of the fetus and the changes which take place accordingly.
Amongst the stages of pregnancy, first trimester is the one in which the rapid growth in the fetus takes place. It is from 1st till 12th week. As it is the start of pregnancy, hence, many hormonal changes take place. The first week starts from the day of fertilization.
During the beginning of first trimester, certain changes such as nausea, tiredness, cravings, mood swings, weakness and constipation will be noticed in the mother. Moreover, enlargement of breasts is also seen with the nipples and areola becoming darker. As the breast enlargement takes place, breasts are also likely to become tender.
This trimester continues from 13thweek up till the 28th week. During this trimester, the feelings nausea and fatigue are known to fade away. Moreover, the first move of the baby is felt between 18th to 20thweek. In second trimester, pain in certain parts of the body occurs such as in back bone, hip bone or thigh pain.
This pain is due to the changing posture of the body of mother as the fetus grows. Other than this, mask of pregnancy, that is patches on cheeks, lips and forehead, also occur during this trimester. The face, ankles and feet also tend to swell. Whereas, the baby is concerned, organ maturation of the fetus takes place during this trimester. Also, the baby is able to hear by then. By the end of second trimester, if the baby is delivered prematurely, there are the chances of his/her survival.
This is the last one amongst the stages of pregnancy. It continues from 28th week and up till 40th week. The size of the baby is quite large by this trimester. Due to which the abdomen of the mother greatly increases and reduces the lung capacity. Hence, at this stage, the mother feels breathlessness and tiredness and due to the enlarged size of the baby, it becomes difficult for her to carry the extra gained weight.
Heartburn is also experienced during these weeks. Towards the end of pregnancy, the baby’s head begins dropping down towards the pelvis. During the third trimester, the nipples begin to secrete a watery substance known as colostrum and false contractions occur.