How to Know Gestational Age in Weeks and Months

To know exactly how many weeks of pregnancy you are and how many months it means you need to calculate the gestational age and for this you only need to know the Last Menstruation Date (DUM) and count in a calendar how many weeks there are to the current date.

The doctor can also always inform corrected gestational age, which is the date suggested on the ultrasound performed at the prenatal appointment, to accurately indicate how many weeks the woman is pregnant and what the Probable Date of Delivery.

It is also possible to calculate the gestational age by indicating only the first day of the last menstrual period, to know how many months you are, how many weeks of pregnancy this means and on which day the baby will probably be born:

What if I do not know the date of last menstruation?

When the woman is not sure what the last menstrual day was, the safest way to know how many weeks of gestation is and what the probable date of delivery is through ultrasound or 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, is considered after the 12th week of gestation and ultrasound requested by the gynecologist.

Learn about other tests that are performed during pregnancy.

How to calculate gestational age in weeks

To calculate gestational age in weeks, note the date of the last menstruation on a calendar. Every 7 days, as of this date, the baby will have another week of life.

For example, if the first day of the last menstrual period was 11 March and the result of the pregnancy test is positive, to know the gestational age, one should begin counting the pregnancy from the 1st day of the last menstrual period and do not the day the sexual relationship occurred.

Thus, if on March 11, which was the DUM, it was a Tuesday, the next Monday the following is completed 7 days and totaling 7 in 7, if today is April 16, Wednesday, the baby is with 5 weeks and 2 days of gestation, which are 2 months pregnant.

The calculation is made so because although the woman is not yet pregnant, it is very difficult to define exactly when fertilization occurred, because sperm can survive up to 7 days in the woman's body before fertilizing the egg and actually initiate the pregnancy.

How to know gestational age in months

According to the Ministry of Health (2014) to know the gestational age, converting the weeks into months, it should be noted:

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 the age of 41 weeks, the doctor may choose to induce labor with oxytocin in the vein.

Also see how the pregnancy is week after week.

How to calculate the probable date of the baby's birth

To calculate the probable date of delivery, which should be around 40 weeks after the DUM, it is necessary to add 7 days to the DUM, then count 3 months back and then put the following year.

For example, if the DUM was March 11, 2018, by adding 7 days, the result is March 18, 2018, and then decreases 3 months which means December 18, 2017 and adds another 1 year. So in this case the Preceded Date of Delivery is December 18, 2018.

This calculation does not give the exact date of the baby's birth because the baby can be born between 37 and 42 weeks of gestation, however, the mother is already informed of the likely time of the baby's birth.

Baby Growth

During each week of gestation, the baby grows about 1 to 2 cm and gains about 200 g, but in the third trimester it is easier to notice this rapid growth, since the fetus is already with the organs formed and your body starts to concentrate, especially in accumulating fat and preparing for the time of birth.