To determine when conception likely occurred and how many weeks pregnant one is, the standard approach is to first identify the first day of the last menstrual period (LMP), then calculate gestational age from that date. Gestational age usually includes about 2 weeks before conception actually happens, as it counts from the start of the last period. Conception typically occurs between about 11 to 21 days after that first day of the last period. To calculate conception date more precisely:
- If the LMP date is known, add about 11 to 21 days to estimate the conception window.
- If only the due date is known, subtract 280 days (40 weeks) to find the LMP, then add 11 to 21 days from that.
- If the current gestational age is known, subtract that from the current date to find the LMP, then add 11 to 21 days.
Gestational age is counted in weeks starting from the LMP to the current date, not from conception. Pregnancy typically lasts around 40 weeks from the LMP and about 38 weeks from conception. To specifically answer the questions:
- The conception date is roughly 11 to 21 days after the first day of the last menstrual period.
- The number of weeks pregnant is calculated from the LMP to the current date, with one week being 7 days.
To provide exact values for conception date and weeks pregnant, please provide either your last menstrual period date, your estimated due date, or your current gestational age (number of weeks) to proceed with a specific calculation. Otherwise, the above general methods apply.
