You can find out how far along you are in pregnancy by counting from the first day of your last menstrual period (LMP), using ultrasound measurements, or by trying a home pregnancy test with a “weeks indicator”.
Methods to Determine Pregnancy Stage
Last Menstrual Period (LMP)
Most healthcare providers calculate pregnancy duration from the first day of your last menstrual period. This approach assumes a regular cycle, and to estimate your due date, count 280 days (40 weeks) from the LMP. This method works best for those with cycles ranging from 28 to 38 days.
Ultrasound Scan
An early ultrasound, typically between weeks 9 and 13, measures the developing fetus and precisely estimates how many weeks pregnant you are—even if you do not remember your LMP. Ultrasound dating is considered highly accurate, especially if you have a regular cycle.
Pregnancy Test with “Weeks Indicator”
Certain advanced home pregnancy tests can roughly indicate whether you are one to two, two to three, or three or more weeks pregnant. These are more general estimates and should be confirmed by a doctor or through ultrasound for precision.
Helpful Tools and Apps
- Online pregnancy calculators and apps can quickly estimate your pregnancy stage after you enter the first day of your last period.
- Your doctor may also revise your estimated due date later if an ultrasound shows the developing baby’s size is significantly different than expected using the LMP method.
Healthcare providers recommend seeing a doctor for an accurate assessment, especially if your periods are irregular or if you’re unsure about your LMP.
