Calculating the Length of Pregnancy

出生前DNA鑑定

Non-invasive prenatal paternity testing (NIPPT) can be done from the 8th week of pregnancy on. Please use this page to calculate the length of your pregnancy.

It is not uncommon for the birth of a baby to be a week before or later from the expected due date.

It is said that only 5% of babies are actually born on the exact due date. In order to calculate the accurate length of a pregnancy, it is necessary to have an obstetrics and gynecologist measure the size of the fetus.

Even then, it is difficult to accurately specify ovulation date, fertilization date and other factors as there are large differences in menstrual irregularity among individual women.

Furthermore, if a woman has relations with multiple men within the week an egg is fertilized, it is impossible to calculate from the fertilization date who the father is. In this situation, it is necessary to have a DNA test done to find the answer.

Calculate the length of pregnancy by simply entering in dates below.

By entering today`s date and the date of your last menstrual cycle, you can calculate the length of your pregnancy.

Clicking the fields below will open a calendar for choosing dates.


Fetal cells can be detected in the pregnant mother`s blood from the 6th week of pregnancy on. The amount of fetal cells present continues to increase over time until around the 14th week, and once a certain amount is accumulated it remains at that level without increase until delivery.

Overseas there have been reports of successful prenatal paternity tests done at the 7th week of pregnancy, however we request that blood samples be collected from the 8th week on.

Although unlikely, if the first test is unsuccessful, we offer to do a re-test for free and cover all sample shipping fees.

It is important to note that when counting the weeks of a pregnancy, the egg is not actually fertilized until the 2nd week of pregnancy. From the 3rd week, the fertilized egg is implanted in the uterus, and from the 4th week it is possible to use HCG home pregnancy tests.

There are some DNA testing facilities out there that advertise that they can test from the 6th week of pregnancy, however there is no evidence that that is possible.

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