Your due date is calculated as 40 weeks (280 days) from the first day of your last period (assuming a 28 day cycle). Therefore, your period and ovulation are counted in the first two weeks of your pregnancy. This means that, if you deliver on your due date, your baby is actually 38 weeks old, not 40.
Why Isn’t My Conception Date Used In Estimating My Due Date?
Even if you were tracking your ovulation, and only had sex once during your fertile period, it’s impossible to know the exact date you conceived. This is because it’s possible for the sperm to survive inside you for a few days, and for fertilization to occur anywhere up to five days after you had sex.
Why Are Due Dates Only Estimates?
Due dates assume a 28-day cycle, and doesn’t take into account irregular periods or longer cycles. Ultrasounds can help more accurately date the pregnancy.
If Due Dates Are Only Estimates, Why Are They So Important?
Due dates are more important as a guideline for the care of mother and baby, and help guide when to have certain prenatal tests, such as the Harmony Test.
What Might Change My Due Date?
As mentioned before, irregular periods and longer cycles are not taken into account when your due date is first calculated at your doctor’s office. The only way to be more accurate about the date of your pregnancy is to have an ultrasound scan. Dr Penman offers scans from 6 weeks of pregnancy. To read more on the scans he offers and find out which one would be right for you, please follow this link.
Should I Be Worried If I Go Over My Due Date?
In late pregnancy, ultrasound scans may indicate baby’s growth is under or over what was originally estimated. However, by this point, assuming you’ve already had a number of scans conducted, your due date is unlikely to change by weeks – perhaps by a few days only.
Going over your due date can be dangerous for a number of reasons, including that the placenta stops functioning as effectively, and prevents baby from receiving the required oxygenated blood and nutrients.
However, doctors in the UK only become concerned about the risks associated with going over your due date when you are more than 10 days overdue. In this case, you can discuss various options, such as medically inducing labour.
What Is The Likelihood My Baby Will Be Born On Time?
Doctors define a “full term” pregnancy as between 39 weeks and 40 weeks and 6 days. Babies born between 37 weeks and 38 weeks and 6 days are considered “early term”, whilst babies born after 41 weeks are considered “late term”.
Assuming an uncomplicated pregnancy, most babies are born within two weeks either side their due date.
How Can I Book A Pregnancy Ultrasound?
Dr Penman offers a number of baby scans from 6 weeks of pregnancy. To book your appointment, please click on the button below.