How pregnancy weeks are counted in months?
Many mothers who become pregnant and find out that they have a new life in their bellies will be counting down the days anxiously for the day they give birth.
However, there are cases in which women have doubts about the expected pregnancy week and the expected delivery date given by the doctor.
It is a good idea to learn how to calculate and count the number of weeks of pregnancy in order to know about the mother’s body and the growth rate of the baby in the womb.
This article also explains how to calculate the expected date of birth and how to classify it by gestational week. Moms and dads who want to know about the number of weeks pregnant should use this as a reference.
How to count pregnancy weeks (months)
Gestation weeks are a unit to measure the progress of pregnancy. There are two ways to count the progress of pregnancy: gestational weeks and gestational months.
What you need to know here is:The number of weeks of pregnancy is full, and the number of months of pregnancy is counted by counting.That’s what it means.
In other words,When you reach the 1st day of pregnancy, you are on the 0th week and 1st day of pregnancy, and you are 1 month pregnant.It will be.
With these principles in mind, we will explain the concept of “gestational age after fertilization,” which is calculated from the day of ovulation, and “gestational age after menstruation,” which is calculated from the first day of the last menstrual period.
Calculated from the day of ovulation [Fetal age after fertilization]
The method of calculating the number of weeks of pregnancy from the day of ovulation is called gestational age after fertilization. This calculation method counts the day of ovulation as 2 weeks and 0 days of pregnancy.
However, in order to calculate the fetal age after fertilization, the day of ovulation must be determined. This calculation method can only be used when the day of ovulation has been confirmed using basal body temperature or ovulation test drugs, so it is not a very common counting method.
Therefore, in many cases, the number of weeks and months of pregnancy is calculated based on the postmenstrual gestational age, which will be introduced next.
Calculated from the first day of the last menstrual period [Postmenstrual gestational age]
The method of calculating the number of weeks of pregnancy from the first day of the last menstrual period before pregnancy is called postmenstrual gestational age.
in this case,Please note that the calculation is not based on the day your menstrual period ends, but rather the first day of your menstrual period is considered 0 weeks and 1 day of pregnancy.
Since it can be calculated as long as you know the menstrual period immediately before pregnancy was discovered, it is currently used as a major calculation method by medical institutions.
How to calculate the expected date of birth [Naegele estimation method]
Once you know how many weeks pregnant you are, you can also calculate your due date.
The gestation period is generally 10 months (40 weeks and 0 days of pregnancy).
It’s not just a matter of counting days at a time. The calculation is a little complicated because the menstrual cycle is 28 days and this is converted into one month.
This is where the Naegele estimation method, a method of calculating the expected birth date, comes into play.
The Naegele estimation method calculates the expected birth date as follows.
■ Birth month
If the last menstrual period was between January and March, +9
If the last menstrual period was after April, -3
■Date of birth
+7 on the first day of the last menstrual period
You can calculate your expected birth date using the method above.
■(Example) If January 1st is the first day of your last menstrual period
Month of birth…1+9=October
Date of birth…1+7=8th
Expected date of birth…October 8th
■(Example) If April 1st is the first day of your last menstrual period
Month of birth…4-3=January
Date of birth…1+7=8th
Expected date of birth…January 8th (next year)
You can easily calculate your expected delivery date, so if you know the first day of your last menstrual period, why not try calculating it?
How to calculate the number of weeks pregnant when you have irregular periods or don’t know the date of your last menstrual period
The counting and calculation methods introduced so far are based on people whose menstrual cycle is 28 days. Therefore, for people whose menstrual cycle is not 28 days, there will be an error.
Also, people whose menstrual cycles are unstable and who do not know the first day of their last menstrual period cannot calculate the number of weeks pregnant.
In such a case,An ultrasound test will determine the week of pregnancy based on the growth and size of your baby.
If you do not have a 28-day menstrual cycle or do not know the first day of your last menstrual period, it is best to first visit an obstetrics and gynecology department and have your doctor determine your pregnancy week.
At what gestational age should you take a pregnancy test?
When calculating the number of weeks pregnant, the question that comes to mind is, “At what week should I take a pregnancy test?”
Many pregnancy tests allow testing from four weeks after the first day of your last menstrual period. This is because it detects the hormone human chorionic gonadotropin (hCG), which is secreted only during pregnancy.
Although there are individual differences,If you are pregnant, it is estimated that hCG will be released sufficiently to be detected by a test drug after the 4th week of pregnancy.
However, pregnancy tests alone cannot determine abnormal pregnancies such as ectopic pregnancy. A normal pregnancy can only be determined by checking the condition of the fetus using an ultrasound or other means.
In the case of an abnormal pregnancy, the mother’s body is also at great risk. Therefore,Even if you detect pregnancy using a commercially available pregnancy test, you should immediately take a pregnancy test at your obstetrician and gynecologist.
Pregnancy classification/birth classification by gestational week
Similar to the number of weeks of pregnancy, the stages of pregnancy, such as early, middle, and late stages, are used to count the progress of pregnancy.
There are also classifications based on the time of birth as the birth approaches.
Next, let’s take a look at the pregnancy classification and childbirth classification that you should know along with the number of weeks of pregnancy.
Pregnancy classification
During pregnancy, the first trimester is 0 to 15 weeks (1 to 4 months of pregnancy). 16th to 27th week of pregnancy (5th to 7th month of pregnancy) is the second trimester. The period of 28 weeks or more of pregnancy (8 months of pregnancy or more) is called the third trimester.
Birth classification
When it comes to childbirth, there are also divisions, and the period when the baby in the womb has grown properly and is able to survive in the outside world is called the full-term birth period. Based on this term, birth before term is called preterm birth, and delivery beyond term is called overterm.
The gestational weeks for preterm birth, term birth, and postpartum period are as follows:
| premature birth | Pregnancy 22 weeks 0 days to 36 weeks 6 days |
| full term | 37 weeks 0 days to 41 weeks 6 days |
| overbirth period | 42 weeks 0 days ~ |
After the postpartum period, the baby becomes too large and it becomes difficult to give birth naturally, or it becomes difficult for the baby to stay in the womb, so there are many cases where medical intervention is required, such as induced labor or caesarean section. Masu.
Questions about calculating pregnancy weeks
Finally, we will explain questions about how to count the number of weeks of pregnancy (months of pregnancy).
Not pregnant during 2-3 weeks of pregnancy
When calculating the number of weeks of pregnancy, the menstrual cycle is calculated as 28 days. Since the first day of your last menstrual period is considered week 0 and day 1, there is actually no implantation or even ovulation during this period.
Pregnancy occurs only after the fertilized egg implants, but when calculating the number of weeks and months of pregnancy, the period when the pregnancy was not carried out must also be counted backwards.
The day you had sex is not the day of fertilization.
A common case among people who incorrectly calculate the number of weeks of pregnancy is when they consider the day of sexual intercourse to be 0 weeks and 0 days of pregnancy.
Just because you have sex when you ovulate doesn’t mean you’ll get pregnant that day. Furthermore, it is said that in modern medical science it is difficult to determine the date of fertilization.
When calculating the number of weeks of pregnancy, the start of the last menstrual period is considered to be 0 weeks and 0 days (the first day is 0 weeks and 1 day).This information is important for managing changes in a woman’s mind and body caused by hormones, so it is recommended that you get into the habit of recording things like your basal body temperature on a regular basis.
0 months of pregnancy does not exist
The number of weeks of pregnancy is counted by the number of weeks, and the number of months of pregnancy is counted by the number of full moons. Therefore,In the early stages of pregnancy, expressions such as “0 weeks and 1 day” are used, but “0 months of pregnancy” is not used.
The period from 0 weeks and 1 day of pregnancy to 3 weeks and 6 days is one month of pregnancy, and from 4 weeks and 0 days of pregnancy is two months of pregnancy.
Pregnancy period is not October 10th
When many people hear the term gestation period, they think of October and tenth. Therefore, there are many people who have doubts about the fact that the calculation is made by adding 10 months and 10 days to the number of weeks of pregnancy, but it does not match the expected date of birth given by the hospital.
10/10 days was a term used as a guideline for the gestation period at a time when perinatal medicine was not as developed as it is today.
There is also a theory that it does not represent 10 months and 10 days, but because first-time births are often later than the expected date, the date was added to 10 months and 10 days, making it October 10th.
In modern times, a month is defined as a 28-day menstrual cycle, and 10 months (280 days) is considered the approximate pregnancy period.
The probability of giving birth on the due date is about 2%.
Some moms and dads think that if they calculate the due date from the pregnancy week, the baby will be born on that day, but this is just a guideline.
In reality, the chance of a baby being born exactly on the due date is said to be around 2%.
Also, many people think that even though the probability of a baby being born exactly on the due date is small, there is probably a difference of a few days.
Actually, this is not a sure thing either, as a result of a survey on the number of weeks of delivery (*) revealed that most mothers give birth at 38 weeks.
This is because when calculating the number of weeks of pregnancy, the 28-day menstrual cycle is counted as one month.
Of course, the more or less your menstrual cycle is than 28 days, the greater the error will be.
Please use the expected birth date as a guideline only, and wait for the day when your baby is born with a relaxed attitude while watching over your baby.
summary
The number of weeks and months of pregnancy is important in order to live a life that matches the progress of pregnancy. It is important to know the correct calculation method and counting method.
Learn the correct pregnancy weeks and how to calculate them, and live a healthy life that is suitable for your unborn baby and the period.