This is a very common doubt that most of the pregnant ladies and their families have. The due date is when the pregnancy completes 40 weeks. If periods are regular we can calculate the due date (EDD) by adding 9months and 7days to the first day of the last period (LMP). For example, if LMP is Jan 1st, the EDD is 8th October.

If periods are not regular or the LMP is not available we have to date the pregnancy with ultrasound scan and calculate the EDD from that. This is most accurate with ultrasounds done in first trimester after 7weeks to around 14weeks. After this the reliability of ultrasound to calculate the gestational age decreases.

The EDD is an approximate time beyond which continuing pregnancy increases the risk to the baby. Only about 1in 25 women deliver on due date and most women deliver before this date.

CAN THE DUE DATE CHANGE?

Sometimes doctor may decide to deliver before due date because of risk to baby or mother. For example if the mother has diabetes or high blood pressure or if the baby has growth issue, delivery may have to be planned before due date. EDD given in the ultrasound scans done in the last few months of pregnancy are usually not considered due to the greater margin of error.

WHAT IS TERM GESTATION?

When the pregnancy completes 37 weeks and 6days , it is called a term pregnancy. When labour starts before 37weeks/ it is called a preterm pregnancy. If pregnancy goes beyond 40 weeks it is called a postdated pregnancy.