Track pregnancy progress, baby growth, risks and fertile days.
Many people wonder exactly when their pregnancy began. While pregnancy age is commonly calculated from the first day of the last menstrual period (LMP), actual conception occurs later, around the time of ovulation and fertilization.
Ovulation does not occur on the same day for everyone. Stress, illness, hormonal changes, and cycle irregularities can all shift ovulation timing. Because of this, pinpointing the exact day of conception is rarely possible.
A conception calculator estimates a range of possible days when fertilization may have occurred, as well as a window during which intercourse could have led to pregnancy.
For people with regular menstrual cycles, conception typically occurs between 11 and 21 days after the first day of the last period. This method assumes ovulation happens near the middle of the cycle, which is not always the case.
Estimating conception based on LMP can be less accurate for those with irregular cycles or who do not remember their last period date.
A due date is often provided by a healthcare professional, usually based on early ultrasound measurements. From this estimated due date, it is possible to calculate a likely conception window.
This method is especially helpful when the last menstrual period is unknown or unreliable.
An obstetric ultrasound uses sound waves to create real-time images of the developing embryo or fetus. Early ultrasounds, typically performed around five to six weeks after LMP, are among the most accurate ways to estimate gestational age.
Accuracy decreases slightly later in pregnancy, which is why early measurements are often preferred for dating purposes.
Although the terms are often used interchangeably, fertilization and conception are not the same medically. Fertilization occurs when sperm and egg join in the fallopian tube.
Conception refers to the successful implantation of the fertilized egg into the uterine wall. From a medical and scientific standpoint, pregnancy begins only after implantation has occurred.
In most cases, no. Conception can only be estimated within a range of days, not identified with absolute certainty.
Early ultrasounds are generally more accurate, especially for people with irregular menstrual cycles.
No. Implantation usually occurs several days after fertilization, once the embryo reaches the uterus.