How to count your pregnancy in weeks?

1 min


The beginning of pregnancy

Pregnancy begins when the sperm fertilizes an egg for a woman. When the time of fertilization is unknown, doctors calculate the pregnancy on the first day of the LMP (last menstrual cycle). They estimate 40 weeks of the LMP until the date of birth (Most births occur between weeks 38 and 42). They may also examine the baby to determine the expected date of birth, through ultrasound, which enables to consider the development of the child early in pregnancy.

Pregnancy calculation method

Last Menstrual Period


The age of the baby calculated from the first day of your final menstrual period and not from the date of conception if you have a regular period and knows the first day of your LMP.


Measuring the baby using ultrasound is most accurate in early pregnancy (5 or 6 weeks after your LMP). The best time to estimate gestational age is between the 8th and 18th weeks of pregnancy.

Calculate pregnancy weeks

The only month in which four weeks (28 days) is the month of February, that is, when the year is not a leap year, all other months are either 30 or 31 days, and the following table shows pregnancy in weeks and months:

Pregnancy in month pregnancy in weeks
Zero 1-4
One 5-8
Two 9-12
Three 13-17
Four 18-21
Five 22-25
Six 26-30
Seven 31-34
Eight 35-38
Nine 39-42




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