Enter the first day of your last menstrual period:

Important milestones in your pregnancy:

Please note: these dates are only as accurate as the last menstrual period date you enter. Misremembering the date, delayed ovulation, irregular periods or bleeding during pregnancy may mean that this date does not match your actual gestational age. It should therefore be confirmed against an ultrasound, preferably performed in the first trimester.

Probable date of conception

The period of greatest risk for abnormalities in organ development is between

and .

During the two weeks after fertilisation, harmful exposures affect the baby according to the all-or-nothing rule: if an effect occurs, miscarriage follows; if not, the pregnancy continues. There may be theoretical exceptions.

The period from week 4, the expected date of menstruation, to the end of week 10 is when organs differentiate and develop. Harmful exposures such as medication, alcohol, ionising radiation or infections can cause developmental abnormalities during this period.

Date when organ development begins

Date when most organ development is complete
 

After the end of week 10, the differentiated organs begin growing. Harmful influences such as medication, reduced amniotic fluid, smoking or infections generally cause damage through effects such as stopping or slowing an organ's development or impairing its function.

End of the first trimester, at the end of week 13. The risk of miscarriage decreases significantly from this date.

End of the second trimester, week 27

Week 28 of pregnancy.

From this stage, survival following premature birth begins to improve. This threshold is gradually moving earlier. The gestational age at which survival is considered possible varies significantly between centres and countries.

Your due date at exactly 40 weeks

The chance of giving birth on this exact date is only 5%. Birth most often occurs within the week before or after it.

Your term delivery period is between and .