Knowing the estimated due date can make it easier for you to plan various details of preparation for the birth of your baby. Apart from getting an estimated date of birth from your doctor, you can also estimate it yourself using a pregnancy calculator.
Generally, pregnancy lasts for 37-42 weeks or an average of 280 days (40 weeks), counting from the first day of the last menstrual period. The first day of the last menstrual period (LMP) is the first day of the menstrual cycle. While ovulation occurs approximately two weeks after this period. If during this period the sperm meets the egg until fertilization occurs, then that's when pregnancy begins.
The calculation of gestational age in weeks generally includes two weeks from the HPHT. So if your fetus is four weeks old, then your pregnancy is counted as six weeks. To find out when the baby will be born, you can use a pregnancy calculator using the Naegele formula and Parikh formula.
Naegele's formula
The name of this formula comes from the name of its inventor, Franz Karl Naegele, an obstetrician in Germany who lived in the 19th century. The estimated day of birth (HPL) is calculated based on the first day of your last menstrual period (LMP). Naegele's formula is as follows:
The first formula is used if the HPHT is from January to March. For example, your HPHT is January 21 2018, then your estimated due date is:
Year: fixed 2018
Month: 1+9 = 10
Day: 21+7= 28
Then the estimated day of your baby's birth is October 28, 2018.
The second formula is used if the HPHT is from April to December. So, if the first day of your last period was May 1, 2018 then your estimated due date would be:
Year: 2018+1= 2019
Month: 5-3=2
Day: 1+7= 8
Then the estimated day of your baby's birth is February 8, 2019.
Parikh's formula
Naegele's formula above has a weakness. This formula can only be applied to women with a menstrual cycle of 28 days. What about menstrual cycles of less or more than 28 days? The answer uses Parikh's formula. The calculation method is done by calculating the time of ovulation, which is the length of the menstrual cycle minus 14 days.
For example, HPHT is on January 1, 2018. If the menstrual cycle is 28 days, then calculated using the Naegele formula, the HPL is October 8, 2018. However, if the menstrual cycle turns out to be 35 days, then using the Parikh formula, the delivery date becomes: HPHT + 9 months + (35-21) days = 15 October 2018.
is Result Accurate?
HPHT is not always the right benchmark for calculating the date of delivery. However, other factors are more difficult to predict, such as the first day of ovulation or when the last sexual intercourse led to pregnancy. While HPHT is the most memorable day and recorded by almost all women.
This calculation of the time of birth with this pregnancy formula or calculator is only an estimate. It is very possible if the baby was born earlier or later than the expected date. In addition to these calculations, doctors use ultrasound examinations to support and confirm the results of calculations with formulas. From the results of an ultrasound examination, it can be seen the development of the fetus from time to time until it is even of age for birth.
With the Naegele formula, only 4% of pregnant women give birth on HPL. However, 90% of pregnant women will give birth within 3 weeks around the predetermined HPL. It is perfectly normal for a woman to give birth two weeks earlier or two weeks later than expected.
Women are at risk of giving birth far beyond their expected date if they are pregnant for the first time, do not know exactly when HPHT, are obese, are carrying a baby boy, have family members with a history of late delivery, and have had children with late deliveries. Towards the day of delivery or if it has exceeded the estimated date of birth, usually there will also be calcification of the placenta.
To make sure the results of the pregnancy calculator are correct, you should still consult directly with your obstetrician. In addition to knowing when your baby is born, you can also consult further about the condition of the womb, tips for childbirth preparation, or other things that may be felt during pregnancy.