Calculating Time of Conception and Due Date

How do I go about working out the due date of my child or the conception date?

Our gender test can only be carried out starting at 9 weeks, counting from the first day of your last menstrual period (LMP)

You can use our pregnancy calculator to help you calculate your dates. We always recommend consulting your gynecologist or family doctor should you be unsure.

Some women have very irregular period and thus determining the date of their last menstrual period can be difficult. A woman begins ovulating about 12 to 16 before her period and on average can get pregnant in any of approximately 5 days out of every month when she is at her most fertile. One can calculate the age of the baby from the last menstrual period (LMP) – the result of this calculation will provide the gestational age. Importantly, the exact date of conception is almost impossible to know. Typically, the baby will be due 40 weeks after the first day after your last menstrual period

Conception can sometimes be a bit ambiguous simply because fertilization does not necessarily occur immediately after intercourse, but rather, it is possible for sperm cells to live in the a woman’s reproductive ducts for up to 5 days from the time of intercourse.  Despite this, as mentioned, you only need an approximate idea of the conception date.

If you have intercourse with more than one man in a very short time it will be impossible to tell who the father of the baby is without a paternity test.

What other methods are there for calculating gestational age?

An ultrasound can give a fair idea of how far into the pregnancy one is and thus, a good idea of the time of conception but not the exact date. An ultrasound measures the size of the baby somewhere in the 5th or 6th week after the LMP. Using the first day of the LMP is always the most accurate method although it is not unusual for many women to only have an approximate idea.  An ultrasound to measure the baby’s age is generally most accurate in the earlier stages of pregnancy; in fact, the best time to calculate gestational age is by carrying an ultrasound between the 8th and 18th week.

Exceptions: In-Vitro Fertilization

Women who have undergone in-vitro fertilization (IVF) or artificial insemination will know the exact date of conception.  Women who have forgotten the day of the last menstrual cycle will also not be able to determine time of conception using an ovulation calendar; they can however, opt for the ultrasound as a means of sex prediction of the baby.

In some cases the size of the child may complicate matters when determining gestational age using an ultrasound. The baby may be unusually big or small and moreover, sometimes the size or height of the uterus does not accurately help predict the gestation age and does not coincide with the time of pregnancy.

Important Note:

You need to provide an accurate date of conception and have a fairly accurate idea of the stage you are in your gestation. If you deliberately or accidentally provide erroneous details the test might fail and we do not hold ourselves responsible in such circumstances. Our gender test is extremely accurate so as long as all steps are followed. Get additional information about sample collection and precautions.