Gestation is the time between conception and birth during which a baby grows and develops in the uterus of the expectant parent. 


The gestational age of a pregnant woman is often stated as a mix of weeks and days. Simply put, gestational age refers to the stage of your pregnancy. It is commonly timed in weeks from the beginning day of your last menstrual period (LMP) to the current date.


Gestational age is used to predict a likely due date, influence obstetrical treatment and testing, and assess the baby’s health at delivery. In addition, it is used as a guideline to determine if the baby is growing normally and when specific prenatal examinations should be performed. 


Babies born smaller or larger than expected for their gestational age may require closer monitoring.


An Overview of Gestational Age


Gestational age can be calculated either before or after birth.


Your doctor will use an ultrasound to measure the size of the baby’s head, belly, and thigh bone before delivery. This indicates how well the kid develops in the mother’s smothering womb.


After delivery, gestational age can be determined by examining the baby’s weight, length, head size, vital signs, reflexes, skin, posture, muscle tone, and hair condition.


If the infant’s gestational age results after delivery match the date on your calendar, the newborn is considered gestationally suitable (AGA). AGA newborns have more minor issues and die at a lower rate than babies who are tiny or big for their gestational age.


Full-term babies born AGA will typically weigh between 2,500 grams (approximately 5.5 pounds or 2.5 kg) to 4,000 grams (about 8.75 lbs or 4 kg).


Moreover, infants weighing less than a kilogram are considered tiny for their gestational age (SGA). Whereas infants weighing more than a certain amount are termed significant for their gestational age (LGA).


How to Understand Gestational Age 


The first day of your last menstrual cycle is the LMP. After that, pregnancies are measured in weeks, beginning with the first day of the LMP. 


If menstruation is normal and lasts 28 days, and ovulation usually occurs on day 14 of your cycle, conception occurs around two weeks after the LMP. 


These two weeks are added to pregnancy for gestational age counting as a more straightforward way than tracking from ovulation or fertilisation.


However, this estimate is not always correct. It does not account for menstrual cycle fluctuations, ovulation variances, and patients’ imprecise recollection. 


Determine Your Due Date 


A due date calendar or calculator can assist pregnant women in determining the due date of their child.


To determine your due date, multiply the first day of your LMP by 280 days (40 weeks) (if you have a 28-day cycle).


Conception Date 


Based on ovulation, date of conception, and ultrasound data, many calculators can help you calculate your due date. In addition, people who use assisted reproductive technologies and embryo transfer can use specific calculators to anticipate their due dates.


When a baby is conceived, this is the conception date. Because sperm may survive in the vaginal canal for three to five days, pregnancy can occur up to five days following sexual contact. 


Delivery Date


The day a person delivers birth is referred to as the delivery date. However, a person’s delivery date may deviate from their due date for various reasons. 


A woman might go into labour before or after her due date, require an emergency caesarean section, or be induced. These variables might cause the delivery date to diverge from the due date.




Ultrasounds, also known as sonograms, are used by doctors to measure the baby in the uterus during pregnancy. It is a medical procedure that employs high-frequency sound waves to get live pictures from within your body. 


During the test, waves travel through the body, colliding with tissues and reflecting off them. These reflected impulses are sent into the system and turned into images. All of these stages take place in real-time.


Health care experts and technologists can confirm a baby’s sex, check on their health, rule out genetic abnormalities, measure their growth, and calculate their fetal age by looking at a live image. 


An ultrasound can also aid with operations like amniocentesis, which involves taking a sample of amniotic fluid and cells using a needle.


Importance of Gestational Age 


Gestational age is used to predict a likely due date, influence obstetrical treatment and testing, and assess the baby’s health at delivery. 


It is used as a guideline to assess if the baby is growing normally and when specific prenatal examinations should be performed.


Gestational age is significant because it guides prenatal care. It is a critical starting point for providers to:


  • Analyse foetal growth
  • Determine the due date of the baby.
  • Prenatal tests and screenings should be scheduled and evaluated.
  • Treat the causes of preterm and post-term birth.


Foetal Age vs Gestational Age


Foetal age is estimated from conception, whereas gestational age is calculated from the first day of your previous menstrual period. This happens during ovulation; therefore, foetal age is approximately two weeks behind gestational age.


This is the foetus’s actual age. However, it is a less exact method of measuring pregnancy since it is hard to tell when conception occurs in humans in most circumstances.




Here’s some additional information that will further your knowledge regarding gestation. 


How do you calculate gestational age?


Doctors calculate gestational age based on the mother’s last menstrual cycle and first trimester ultrasounds. The embryo’s age and the day of conception determine gestational age in pregnancies arising from assisted reproductive technologies such as IVF. 


What is the accuracy of ultrasounds in detecting gestational age?


Early pregnancy ultrasounds are the most reliable approach to assessing gestational age, especially for pregnant women who have a history of irregular menstrual cycles.


What exactly is the distinction between gestational age and weeks pregnant?


Gestational age is the period from the pregnant woman’s last menstrual period (LMP) to the present (and, as a result, includes the two weeks before conception occurs). It denotes how far the pregnancy has advanced. 


Most individuals use gestational age to describe how many weeks pregnant they are. On the other hand, the foetal period begins at conception and exclusively defines the growing foetus’s age.




The term “gestation” relates to the length of time you are pregnant. It’s also used in various other terminologies about multiple elements of pregnancy.


Gestational age is a valuable tool for assisting your doctor or midwife in providing the best prenatal care during your pregnancy and assessing your baby’s progress. 


It also allows you to track your baby’s development week by week. What could be more thrilling than picturing your kid sneezing or opening their eyes in the womb? 


Your doctor can use gestational age to determine if your baby is developing typically.