A trimester is three months, which is equivalent to twelve weeks. In the gynecological calendar, the trimester is 93.3 days, given that the entire pregnancy lasts 280 days. It is considered from the first day of delayed menstruation or from the last day of the menstrual cycle.
Duration of pregnancy by calendars
If there are 365 days in a year, then the pregnancy is 9 months. However, in February, 28-29 days, every second month has 31 days, and here it is quite difficult to determine the calculations. To calculate the date of birth, arithmetic alone is not enough. The obstetric calendar consists of months, each of which has 28 standard days. In general, this is ten months, and trimesters are not 90 days, but 93. Even if you count the average of the first three months from January to March, you get 92 days, only February compensates for the days.
How to determine the date of birth and labor?
Given the difference in the number of weeks, a pregnant woman may incorrectly calculate the estimated date of birth. To do this, resort to two methods:
- If the date of conception is known, 264 days are added to it.
- If the date of conception is unknown, then from the first day of menstruation 3 months are counted back (taken away) and seven days are added. For the convenience of calculations, you can first add a week, and then take away the trimester.
For example, the last day of menstruation was December 1. So from September 1 (taken away the trimester) we count +7 days, and it turns out September 7-8 - this is the estimated date of birth.
The surest way to find out the date of birth
And today, the most reliable way to set the date of birth is considered an ultrasound. According to its results, it is clearly visible how the baby develops and grows for 9 months. If the trimester is three months, then from 6-7 weeks after conception , the diagnostic doctor can tell you exactly when to replenish. It is worth noting that children are not always born on time, and at 33-35 weeks you need to undergo an appropriate ultrasound. It is necessary for:
- establishing whether the child is developing correctly;
- whether to expect an advantage;
- whether a caesarean section will be needed;
- how much the baby weighs;
- how the fetus develops;
- where the baby is located relative to the uterus.
Therefore, it is important to understand that trimesters are how many weeks are included in 1/3 of the duration of pregnancy. You should not refer to the standard definitions that three months from the beginning of the year is the correct countdown, and everything else is only part of the previous and subsequent periods. Trimesters at the school also have three quarters of 3 months each, and the summer quarter has vacations.
Trimester egg development
If you move away from arithmetic, you can systematically consider how the cell develops and conception occurs. Fertilization takes from 24 to 96 hours, so if you have an unwanted pregnancy, you should use urgent methods of contraception in the first 24 hours. The male sperm lives 5 days, and from the first minutes begins to move towards the ovum. The fusion of the male and female nucleus into a cell means fertilization. Next, cell division occurs, after which the embryo moves through the tubes into the endometrium of the uterus.
The egg is attached to the wall and after a week you can start the countdown. Pregnancy has begun, so the first trimester has come. Further, the fetus develops monthly and increases in size.
First trimester - how life begins
The first stage is the most difficult and exciting. In these three months, you should take care of yourself and the fetus. Several cells interconnected develop from day to day. Chorionic gonadotropin (hCG) is produced. It sends a signal to the corpus luteum about the need for the production of progesterone. The hormone enters the urine, the reaction is reflected in pregnancy tests and when taking tests. The first trimester is how many months? Everyone has the same thing - 3 calendar months and 3.4 obstetric months. A tube of the nervous system in the child appears, two thickenings, the liver and brain are formed.
- The outlines of the baby also become visible.
- There are "cells" for the eyes and nose.
- Fingers are already forming with the nail plate.
By the end of the third month, a heart is formed from one chamber, and by the beginning of the second trimester, you can establish a heartbeat when undergoing an ultrasound.
Second trimester - organs develop
When organs of the digestive system are formed, the fetus actively develops and gains weight. Not so fast, but the brain is rapidly forming. The heart already consists of 4 chambers, and the respiratory system is completely "ready" for work. By the middle of the second trimester, by the 5th month, the fetus begins to move its legs and arms. Blood vessels are not yet perfect, but the cartilage tissue is already gradually replaced by bone.
By the end of the second trimester, the baby reaches a size of 18-24 cm (depending on genetics). During this period, mom should focus on taking vitamin C, glucose and iodine. Avoid infections and viral diseases. At the end of the sixth month, the baby will be able to distinguish sharp sounds, startle, react to light, smell. He can already distinguish mom’s voice from extraneous sounds. For a child, the 2nd trimester of pregnancy is very important, because in these weeks he is practically preparing for the birth. At birth at 7 months, the baby is considered a viable and full-fledged baby.
Third trimester - the laying of the senses and weight gain
No wonder doctors say that the main set of weight occurs at the 9th month. Moms should carefully monitor the diet:
- By the third trimester, the baby already weighs 1,500 grams, and if the mother eats actively, then during the last 3 weeks of pregnancy the baby will add 35 grams per day. And this significantly increases the chance for caesarean.
- Babies by the 7th month can open their eyes and see.
- The respiratory system is being improved.
- Swallowing reflexes are formed. Often, children swallow amniotic fluid.
- Hiccups in the fetus may appear.
By the 8th month of life inside the womb, the baby is 40-45 cm tall and weighs approximately 2,200 grams. The ninth month is “useless” for the baby, as he “lives out” his days inside, preparing for the birth. Its skin becomes smooth, a protective fluff appears, a surfactant in the lungs actively lubricates the alveoli so that they do not stick together. At the first breath, they will open, and the baby will experience a slight tingling sensation, from which it will cry.
Tenth obstetric month - sacrament of birth
When the 40th week comes, the baby actively moves out through the birth canal. The placenta is the only living organism in the world that lives for 9 months, after which it dies. This is the "house" for the baby, its environment, and the older it is, the sooner the baby will meet his parents. What is a trimester for an obstetrician who considers the 10th month a stage in the birth of a child?
These are 18 additional days, which make up the difference between a period of 9 and 10 months. If the pregnancy is postponed, then the baby will appear at 41-42 weeks. And this is a full 10th obstetric month, which, as a rule, is considered the norm in medical practice. In just a few hours, the baby manages to overcome a serious and difficult path for meeting with his mother:
- lubricant is produced to cover the alveoli;
- baby rolls over;
- the head drops sharply into the bosom of the pelvis;
- the first battle begins;
- the birth canal opens;
- pelvic bones expand;
- opening the cervix is often painful - up to 4 cm have to wait almost 8-10 hours;
- the baby moves down with the help of his mother;
- the head enters the birth canal, expanding the walls of the cervix.
The head is shown, the body is expelled - the baby is born. All these trimesters he lived inside and in an instant found himself on the other side of his "house". A miracle happens - the first acquaintance with mom.