- What if I don't know the date of my last period?
- How to calculate gestational age in weeks
- How to know the gestational age in months
- How to calculate the likely date of baby's birth
- Baby growth
To know exactly how many weeks of pregnancy you are and how many months it means, it is necessary to calculate the gestational age and for that it is enough to know the Last Menstruation Date (DUM) and count on a calendar how many weeks there are to date.
The doctor can also always inform the corrected gestational age, which is the date suggested in the ultrasound performed in the prenatal consultation, to indicate exactly how many weeks the woman is pregnant and what the Probable Date of Childbirth will be.
It is also possible to calculate the gestational age just by indicating the first day of your last menstrual period, to know how many months you are, how many weeks of pregnancy this means and on what day the baby is likely to be born:
What if I don't know the date of my last period?
When the woman is not sure which was the day of her last menstruation, the safest way to know how many weeks of pregnancy she is and what the probable date of delivery is is through ultrasound or through the uterine height, which is what the doctor usually calculates the weeks and months of pregnancy. For this, the amount of Beta HCG in the blood, uterine height, after the 12th week of pregnancy and ultrasound requested by the gynecologist are considered.
Find out other tests that are performed in pregnancy.
How to calculate gestational age in weeks
To calculate gestational age in weeks, you should write down the date of your last period on a calendar. Every 7 days, from this date, the baby will have another week of life.
For example, if the first day of your last menstrual period was March 11th and the pregnancy test result is positive, to know the gestational age, you should start counting the pregnancy from the 1st day of your last menstruation and not the day the sexual intercourse took place.
Thus, if March 11, which was the DUM, it was a Tuesday, the following Monday completes 7 days and adding up to 7 in 7, if today is April 16, Wednesday, the baby is with 5 weeks and 2 days of gestation, which is 2 months of pregnancy.
The calculation is done because although the woman is not yet pregnant, it is very difficult to define exactly when fertilization occurred, as sperm can survive up to 7 days in the woman's body before fertilizing the egg and actually starting the pregnancy.
How to know the gestational age in months
According to the Ministry of Health (2014) to know the gestational age, converting weeks into months, it should be noted:
| 1st Quarter | 1 month | until 4 ½ weeks of gestation |
| 1st Quarter | 2 months | 4 and a half weeks to 9 weeks |
| 1st Quarter | 3 months | 10 to 13 and a half weeks of gestation |
| 2nd Quarter | Four months | 13 and a half weeks of gestation to 18 weeks |
| 2nd Quarter | 5 months | 19 to 22 and a half weeks of gestation |
| 2nd Quarter | 6 months | 23 to 27 weeks of gestation |
| 3rd Quarter | 7 months | 28 to 31 and a half weeks of gestation |
| 3rd Quarter | 8 months | 32 to 36 weeks of gestation |
| 3rd Quarter | 9 months | 37 to 42 weeks of gestation |
Usually the pregnancy lasts 40 weeks, but the baby can be born between 39 and 41 weeks, without problems. However, if labor does not start spontaneously until you are 41 weeks old, the doctor may choose to induce labor with oxytocin in the vein.
See also what pregnancy is like week by week.
How to calculate the likely date of baby's birth
To calculate the probable date of delivery, which should be around 40 weeks after LMP, it is necessary to add 7 days to LMP, then count 3 months back and then put the next year.
For example, if the LMP was March 11, 2018, adding 7 days, the result is March 18, 2018, and then decreases by 3 months which means December 18, 2017 and adds another year. So in this case the Expected Delivery Date is December 18, 2018.
This calculation does not give the exact date of birth of the baby because the baby can be born between 37 and 42 weeks of gestation, however, the mother is already informed of the probable time of the baby's birth.
Baby growth
During each week of gestation, the baby grows about 1 to 2 cm and gains approximately 200 g, but in the third trimester it is easier to notice this rapid growth, as the fetus has already formed organs and its body starts to concentrate mainly to accumulate fat and prepare for the moment of birth.
