How do I know which gestational week I am in?

Gestational age is counted from the first day of the last menstrual period. The number of completed weeks and days shows which gestational week you are in. For example, 12 weeks + 3 days means the 13th gestational week is underway.

From which day is pregnancy counted?

Pregnancy is traditionally counted from the first day of the last menstrual period, not from the date of conception. This is why the first approximately two weeks of gestational age usually precede conception itself.

How is the gestational week calculated?

Gestational age is counted in calendar days from the first day of the last menstrual period until today. The number of days is divided by 7 – the completed weeks are the whole part and the remainder is the days. For example, 61 days are 8 completed weeks and 5 days.

How many weeks does pregnancy last?

For a standard 28-day cycle, pregnancy is considered to last approximately 40 gestational weeks, or about 280 days from the first day of the last menstrual period.

How is the due date calculated?

For a standard 28-day cycle, 280 days are added to the first day of the last menstrual period. For a different average cycle length, a correction is applied based on the difference from 28 days.

What happens if my cycle is not 28 days?

The calculator adjusts the due date according to the average cycle length. A longer cycle shifts the due date later, and a shorter cycle shifts it earlier.

What does an irregular cycle mean for the calculation?

With an irregular menstrual cycle, the calculation from the last menstrual period may not accurately reflect the gestational age. An obstetrician can refine it through examination and ultrasound.

Can the due date from an ultrasound be different?

Yes. Ultrasound measurement can refine the gestational age and due date, especially with an irregular cycle or an unknown date of the last menstrual period.

How accurate is the estimated due date?

This is an approximate date. Ovulation does not always occur on the same day, the cycle may be irregular, and ultrasound assessment of gestational age may lead to a correction of the due date. Only a small proportion of births occur exactly on the estimated due date.

When may the doctor change the due date?

An obstetrician may refine or correct the gestational age based on the medical history and ultrasound measurements. The calculation from the last menstrual period is only an orientation.