To count pregnancy after a missed period, the standard method is to calculate gestational age starting from the first day of your last menstrual period (LMP). This is because the exact date of conception is often unknown, so healthcare providers use the LMP as a reference point. Here is how you can do it:

• Identify the first day of your last menstrual period.
• Count forward 40 weeks (or 280 days) from that date to estimate your due date. This period includes about two weeks before ovulation and conception actually occur, so the pregnancy duration counted this way is longer than the actual fetal age by about two weeks

For example, if your last period started on January 1, adding 280 days would give you an estimated due date around October 8. If you know your conception date precisely, you can count 266 days (about 38 weeks) from that date to estimate your due date, which reflects the actual fetal age

. Regarding how far along you are after a missed period:

• A missed period usually occurs about 4 weeks after conception, so if you have just missed your period, you are approximately 4 weeks pregnant by gestational age

• To calculate the exact number of weeks and days pregnant, count the days from the first day of your last period to the current date and convert that into weeks and days (e.g., 44 days = 6 weeks and 2 days)

Pregnancy tests are most accurate when taken at the time of a missed period or later, as by then the pregnancy hormone hCG is usually detectable in urine

. In summary:

• Use the first day of your last menstrual period as the starting point.
• Count forward 40 weeks for your due date.
• After a missed period, you are generally about 4 weeks pregnant.
• Use online pregnancy calculators or consult a healthcare provider for precise dating and confirmation via ultrasound.

This method is widely used by healthcare providers and pregnancy calculators to estimate how far along you are and your expected due date