Gestational Age vs. Fetal Age: What is the Difference?

Many people believe that the gestational and fetal ages are the same; however, they are not. There is no doubt that gestational age and fetal age are the most frequently discussed topics regarding the length of a pregnancy. Basically, both of them aim to determine the due date of the pregnancy.

If you want to learn more about the difference between gestational age and fetal age, read our post because we’ll show you an easy indicator to tell the difference. Let’s check it out!

Gestational Age vs. Fetal Age: What is Difference?

pregnancy stages illustrations
Pregnancy Stages Illustrations

The significant difference between gestational age and fetal age is in the time when both of them started.

  • Gestational age is the age of the pregnancy that is taken from the beginning of the woman’s last menstrual period (LMP).
  • Fetal age is the age at which the baby actually grows, starting at conception.

The point is, the gestational age includes an additional two weeks when a woman does not yet have a pregnancy, while the fetal age is calculated after conception. In general, gestational age refers to menstrual age, whereas fetal age refers to conception age.

What is Gestational Age?

After undergoing ultrasound, you may find your fetal age is later than your gestational age. Even though both of them are terms used regarding the length of a pregnancy, gestational age is a commonly used term.

Gestational age is calculated from the last menstrual period, which is why it is also referred to as the menstrual period. Pregnancy lasts 40 weeks on average, depending on gestational age.

The regular length of pregnancy consists of three trimesters:

  1. Development stage
  2. Embryonic stage
  3. Fetal stage

The gestational age usually occurs two weeks before the fetal begins to develop. It can be caused by the occurrence of ovulation two weeks after the last menstrual period. It is a more accurate measurement than fetal age because gestational age is calculated based on the last menstrual period.

According to the U.S. National Library of Medicine, babies born “Appropriate for Gestational Age (AGA),” have a lower level of possible complications and lower death rates compared to babies born prematurely.

Full-term babies born with AGA commonly weigh from 2.5 kg to 3.9 kg. The doctor can also calculate the gestational age after birth by examining the condition of your fetus’s skin and hair, length, head circumference, muscle tone, vital signs, posture, and weight.

What is Fetal Age?

Fetal age is a separate unit of measurement from gestational age. Basically, fetal age is the age at which the baby really grows. An obstetrician usually measures the age of the fetus through ultrasound, starting from the baby’s growth, the condition and trimester of pregnancy, the baby’s movement, the baby’s position, the baby’s heart rate, amniotic fluid, and the baby’s health condition.

Read also: 4D Ultrasound: Definition, Benefits, and Procedures

The fetal age is also known as the conceptual age. Ovulation generally occurs two weeks after the last menstrual period. Fertilization basically occurs close to ovulation. That’s why the date of conception is the same as the date of ovulation.

Thus, fetal age is two weeks later than gestational age. However, that’s a less accurate measurement because of the difficulty of calculating the date.


Knowing the fetal age and gestational age will make it easier for you to understand every development and the appropriate stimulation for each stage of your pregnancy. The appropriate stimulation of the fetus will increase fetal brain cells. In addition, the extent of the prospective baby’s brain tissue will depend on how many brain cells are formed.

At each stage of your fetal development, you may always have to figure out how far your fetus is developing, how big he or she is, and what kinds of activities to prepare in an attempt to stimulate your baby’s brain cells.

Leave a Reply

Your email address will not be published. Required fields are marked *