How long does pregnancy last? How many days, weeks and months?

The duration of pregnancy is calculated from the fertilisation of the egg until the birth of a healthy, premature foetus. The exact date cannot be determined with certainty.

Only 1 in 20 babies is actually born on the expected due date.

Frequently asked questions:
What is the length of pregnancy in days?
What is the length of pregnancy in weeks?
How do I calculate the due date?
How are the weeks of pregnancy calculated?

A normal pregnancy lasts on average between 38 and 42 weeks of pregnancy.

At this time, every mom-to-be should be ready for the arrival of the offspring.

The time from fertilization of the egg to the development of a viable baby lasts on average 267-290 days.

In studies, the average length of pregnancy has been accurately determined to be 280 days. This represents 10 lunar months (one lunar month has 28 days).

The pregnancy booklet record also records the week you had the check-up. It will say, for example, 14+2. This means you are currently in week 14 plus 2 days of pregnancy.

What is the difference between fetal and gestational age?

From the day of fertilisation the fetal age, the actual age from conception, starts, which is 38 weeks.

The gestational age of the fetus is given as the first day of menstruation before fertilization, which is also used to calculate the day of delivery - 40 weeks.

Length of pregnancy

For practical obstetric reasons, the length of pregnancy is calculated from the first day of the last menstrual period, even if fertilisation occurred approximately 14 days later.

The exact date of delivery can best be calculated with regular menstrual periods.

With irregular menstruation it is more complicated because we cannot determine the day of fertilisation of the egg.

It is normal for labour to take place 2 weeks before or after the expected due date (40 +/- 2 weeks).

Each pregnancy takes a different length of time because each fetus also takes a different rate.

How many days does a pregnancy last?

From the average length of pregnancy, the actual length may vary. We divide the thresholds into a lower limit of under 240 days and an upper limit of up to 310 days.

If the delivery takes place before the end of the 37th week, i.e. before the end of 259 days of pregnancy, then we speak of premature birth.

If it occurs after the 42nd week of pregnancy, it is called a carry-over.

The lower limit for fetal survival is the 24th week of pregnancy.

Pregnancy period

Pregnancy is divided into three periods, referred to as trimesters.

Trimesters and the main differences:

• The first trimester is from fertilization to the end of the 12th week of pregnancy
  • At the end of the 12th week, the fetus measures approximately 5.4 cm and weighs 14 g.
• The second trimester is from week 13 to week 28
  • the foetus is approximately 37.6 cm and 1005 g at the end of the 28th week
• The third trimester, the last trimester, is from week 28 to the calculated date of delivery
  • the birth weight of the newborn at week 40 is approximately 3462 g and 51.2 cm

You can read more about pregnancy in the article.

How to calculate the length of pregnancy and determine the date of delivery?

If you know the day of fertilization, just calculate 280 days or calculate 40 weeks from the first day of the last menstrual period.

The quickest way to calculate the probable date of delivery is as follows. Add 7 days to the first day of the last menstrual period, one year and subtract 3 months.

For example:
The first day of the last menstrual period was 1 October 2020. To this date we add 7 days and one year, which is 8 October 2021. Then we subtract 3 months and get the result 8 July 2021. The expected date of birth is therefore 8 July 2021.

When will I give birth?

Our calculator will help you find out the approximate date of your baby's birth:
Calculator for calculating the date of birth: when is my due date?

Length of pregnancy by first movements

Every mom-to-be at about 20 weeks of pregnancy eagerly awaits when she will finally feel the gentle movements of her offspring in the form of gurgling, tickling or tingling.

The first movements used to be the basis for calculating the expected date of birth, although it was not very accurate. Nowadays it is no longer even used. This calculation is more of an approximation.

Calculation based on the first movements:

• For a first-time mother, add 5 months + 2 weeks to the day she felt the baby's first movements.
• For a multiparous mother, add 5 months because multiparous mothers feel their first movements approximately two weeks earlier than first-born mothers.

Determining the due date by ultrasound

Determination of the due date by sonographic examination at the 13th week of pregnancy is considered to be the most accurate. If the calculated due date of the last menstrual period differs from the sonographic determination of pregnancy by more than one week, then the due date should be adjusted.

You can read more about ultrasound examinations and fetal measurements in our article.

10 common disorders of pregnancy duration

Disorders of pregnancy duration:

1. A miscarriage is the termination of pregnancy before the 28th week, when the fetus has a weight of less than 100 grams and measures less than 35 cm.

2. A miscarriage can be artificial - induced artificially, by medical intervention at the request of the mother.

3. Abortion may also be spontaneous - spontaneous if it has not been artificially induced and the uterus has expelled the fetus naturally on the basis of some developmental defect of the fetus, malposition of the fetus, its envelope, or a malformation of the nesting. A healthily developing fetus may be expelled from the uterus because of a developmental defect of the uterus or because of an illness of the mother.

4. A complete abortion is considered to be the expulsion of the entire foetal egg by uterine contractions.

5. Usually, however, a part of the amniotic sac remains in the uterus and we speak of an incomplete abortion. Then it is necessary to clean the uterus by curettage.

6. We consider a late miscarriage to be a miscarriage in the 4th-6th month of pregnancy. It can take place as a labor, amniotic fluid drainage, contraction expulsion of the fetus and finally expulsion of the placenta.

7. Feverish abortion takes place with signs of uterine infection and temperature. This condition is very serious and needs hospital treatment.

8. Habitual abortions may have the same causes as spontaneous abortions, but these abortions recur three or more times in a row.

9. Another disorder of the duration of pregnancy is carry-over pregnancy. It is the continuation of pregnancy 10-14 days after the calculated term of delivery. The pregnancy is terminated medically, by administering drugs to induce labour. But if it is unsuccessful, a caesarean section is performed. The baby is born with signs of carry-over pregnancy (wrinkled skin, skin on the feet peels off, nails are already long, the fetus is "overripe").

10. An ectopic pregnancy is a pregnancy that does not take place in the uterus. It occurs when the fertilised egg does not have time to settle in the uterus and remains in the fallopian tube. It begins to nidate, to settle. It does not, however, have the ideal conditions for its development.

In this case, the pregnancy ends in two ways:

• It can end in rupture of the fallopian tube. The woman feels severe pain on one side of the abdomen and eventually collapse and shock. This condition is serious and requires immediate surgical intervention.
• The second possibility is tubal abortion - when the fallopian tube contracts, the fetal egg is discharged into the abdominal cavity or uterus. It turns into what is called a mole. It usually bleeds and blood accumulates in the Douglas space (the area between the uterus and rectum). The woman feels pain alternately in the lower abdomen, bleeds gently or has a brownish discharge. This condition is also acute and requires medical treatment to prevent chronic inflammation.

Pregnancies proceeding successfully outside the uterus are very rare, and fetuses with congenital developmental defects in shape are deformed.

More information in the article.

Lifestyle and the effect on the duration of pregnancy

Lifestyle also has an effect on the length of pregnancy and on fetal development.

Every mother-to-be should lead a proper lifestyle with:

• Adequate exercise
• vitamin intake
• folic acid intake
• a balanced diet necessary for the fetus and for the proper course of the pregnancy(watch out for anaemia)

Avoiding:

• Alcohol
• cigarettes
• drugs
• drugs
• and certain foods such as raw meat, raw eggs, soft and fresh cheese
• limit contact with animals because of possible transmission of toxoplasmosis, listeriosis and salmonellosis
• also avoid possible stress, which has a major impact on the length of pregnancy and often leads to spontaneous abortions or premature births
• avoiding excessive stress on the body
• lifting heavy objects
• hot baths
• sauna - especially in the first trimester