How to count pregnancy weeks?

Pregnancy is typically dated from the first day of your last menstrual period (LMP). This is the standard method of calculating gestational age and is used to determine your estimated due date. This calculation is done by counting forward 40 weeks from the LMP. Several online calculators and smartphone apps are available to simplify this process, but they should only be used as an estimate, and should not replace advice from your healthcare provider.

However, ultrasound confirmation of gestational age, performed by a healthcare professional, is generally more accurate than relying on LMP-based calculations. Your healthcare provider can perform an ultrasound and confirm your gestational age, ensuring the best possible prenatal care plan.