How To Calculate The Gestational Age By Weeks And Months Correctly

How to calculate the correct gestational age for expecting the due date for their baby is interested by women. Attention to the last menstrual period is often the key to find out how to calculate gestational age and the due date for their baby.

Calculate The Gestational Age By Weeks And Months

When you find out that you are pregnant, you will certainly learn how to calculate fetal age to know how many weeks your baby is? When will you give birth? Do not be surprised if your routine pregnancy, the due date for your baby or gestational age changes slightly from your original estimate. You want to know how to calculate the correct pregnancy age? So refer to the following article.

How to calculate the due date for your baby

The due date for your baby will be determined by adding 40 weeks (ie 280 days) on the first day of the last menstrual period. This is done with the assumption that you have 28-day menstrual cycles and it is regular. Two weeks after the first day of “menstrual period” of the last menstrual period, the ovulation just occurs. This is the time when new eggs can conceive. If you give birth on the due date, your baby is only 38 weeks old, not 40 weeks old.

For example, the date of the “menstrual period” of the last menstrual period is December 25th, 2017. Plus 40 weeks, the due date for your baby is September 30th, 2018.

The due date for your baby is only an estimate of when the baby will be born. Only 5% of children are born on the due date. Most babies will be born between 37 and 42 weeks of gestation, usually within one week compared to the the due date.

How to calculate gestational age by weeks

Pregnancy week is based on the last menstrual period. The first pregnancy week will begin on the first day of the last menstrual period. The following weeks add up. This may sound strange but it helps you know exactly when you need medical helps.

There is no way to accurately determine the time of ovulation and conception. Therefore, most people, including health professionals, will judge the date you conceive based on the first “menstrual period” of your last menstrual period.

If you do not know the first day of your last menstrual period or your uneven cycle, how to calculate?

Calculating the due date for your baby by the menstrual period is best if your menstrual cycle is regular, it means that every cycle has 28 days. If you do not remember or your menstrual cycle is uneven, you should wait until the first episiotomy to determine your gestational age by weeks and calculate the due date for your baby. The ideal time for ultrasound is 10-13 weeks plus 6 days.

The estimation of the due date for your baby is accurate only when you have a regular menstrual period of 28 days. For women with shorter or longer menstrual cycles, calculating the due date for your baby under this method will not give reliable results.

What is the trimester?

“Trimester” means “3 months” because most pregnancy occurs during the 9 months,  every pregnancy is divided into 3 trimesters. This is only an effective way to describe changes within your body:

  • The first trimester occurs from conception until your gestation is the 13th week and 6 days. Along with the excitement and anticipation, pregnant women feels tired from the morning sickness.
  • The second trimester is from the 14th to the 27th week of pregnancy and 6 days. During this trimester, the mother will feel better and healthier. The morning sickness almost took away all your strength in the early period are no longer and you will find it difficult to hide your belly grow up.
  • The third trimester occurs when you are 28 weeks pregnant until your baby is born. You will need a lot of energy to help your baby grow strongly as well as fight fatigues.

How to calculate pregnancy weeks after In Vitro Fertilization (IVF)?

Calculating pregnancy week and the due date for your baby will be more accurate than the conventional conception. This is because you know the exact date of embryo transfer or ovulation.

The conventional conception of in vitro fertilization will be calculated by adding 38 weeks (ie 266 days) since the fertilized egg. Another method is to add 38 weeks but subtract the number of days that the embryo is implanted. For example, if the embryo is transplanted for three days, it will subtract 3 days and 4 days, minus 4 days.

Therefore, artificial insemination will help to determine the gestation period and the the due date for your baby more correctly. In addition, you can ultrasound to predict the due date for your baby more accurately.

Weekly and monthly pregnancy chart

If the above calculation is making you crazy, you can use the simple solution:

If you are in the 5th week, it is actually 4 weeks pregnant. Why is that?

A 1-year-old baby means the baby has been born 12 months and she or he is about to start the second year, but she is still considered to be 1-year-old. Similarly, when you pass the first week, you are still considered pregnant for 1 week even though you have entered the second week of pregnancy. For example:

  • During the first week of pregnancy, you will be referred to as not pregnant.
  • During the second week of pregnancy, you will be considered pregnant for 1 week.
  • During the third week of pregnancy, you will be considered pregnant for 2 weeks.
  • The method of calculating gestational age by weeks continues as above.

How to calculate gestational age by weeks and months will give you the most basic view about pregnancy time, the due date for your baby. It is important to know that each person’s pregnancy is different and this is the most common way. Therefore, do not over-rely on its accuracy. If you have any questions about your pregnancy or your due date, ask your doctor if you have a routine pregnancy check up for further information.

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