How many months a pregnancy lasts is a question many expectant mothers are interested in. There is no way to determine the obstetrical term with maximum accuracy, all predictions have a certain probability of error. The birth may be premature, late or on time – regardless of this, you should stick to the recommendations prescribed by your doctor. There are several ways to determine the length of your pregnancy.

It is impossible to tell exactly how many months a pregnancy will last. Doctors confirm that the term of carrying a child is 9 months or three trimesters, which is a kind of norm. Even when the expectant mother goes to the doctor for the first time, the approximate due date is determined. Soon, this date is adjusted on the basis of tests and ultrasound.

How long does pregnancy last

Normal duration

Exactly 40 weeks is the duration of pregnancy in the absence of any abnormalities. It is nine calendar months or ten obstetric months. In general, the term of carrying a baby is 280 days. Timely delivery occurs from the 37th to the 42nd week. Preterm births are considered to be those that began before the 37th week, after the 42nd week – late births. That is, they are considered deviations from the norm.

The duration of pregnancy conventionally consists of two periods: embryonic and fetal. The embryonic period from the time of fertilization lasts until the tenth week (obstetric term is considered). At this point, the fetus is formed and develops in the body of the expectant mother. This includes the formation of tissues, organs, and the placenta.

The fetal period lasts from 11 weeks of gestational age until delivery. During this time, you can notice active growth of the fetus, changes in its proportions, and the development of all organ systems. In addition, the first tremors of the fetus become noticeable.

How long does pregnancy last

On what depends the duration of childbirth

The duration of pregnancy depends on several factors:

  • congenital predisposition;
  • Number of days of menstruation;
  • The timing and activity of the sperm that led to fertilization;
  • the moral and mental state of the pregnant woman;
  • age features of the body.

Analyzing all the above data, doctors calculate the duration of pregnancy. It can be determined by days and weeks. This confirms that for each expectant mother, the terms are set individually.

What can cause preterm labor: the main causes

The obstetric term can not always be accurate. Therefore, preterm birth is considered premature if it begins before the 37th week. The baby in this case is recognized as premature – in this case it needs to stay in a medical facility under the care of specialists for some more time.

The degree of prematurity of the baby is determined by the following scale;

  • 32-36 weeks. Mild degree, the health of the newborn is satisfactory;
  • 28-31 weeks. Medium degree. The baby requires special medical care, so the mother is left under medical supervision;
  • Less than 28 weeks. Severe degree. The health of the newborn is at risk, requiring the use of special equipment and long-term care.
How long does pregnancy last

40 weeks – this is the length of pregnancy is considered “normal”. There are several reasons for giving birth earlier than the appointed term:

Rupture of fetal membranes ahead of scheduleFrequency of contractions more than 8 times per hour
Chorioamnionitis or other intrauterine infectionsMild blunt back pain
Multiple pregnancyPelvic pelvic thrust with aching sensation that increases at night
Fetal or placental abnormalitiesDiarrhea
Uterine abnormalitiesA bloody vaginal discharge
PyelonephritisWatery vaginal discharge

Quite often, it is very difficult to determine why labor started before the recommended duration of pregnancy. It is only worth remembering that a premature birth always carries a risk not only to the woman in labor, but also to her baby. So, giving birth earlier than planned, can lead to intraventricular hemorrhage or impaired neuropsychiatric development.

How long does pregnancy last

Delayed delivery

Delayed labor that lasts longer than the normal duration of the pregnancy is considered abnormal. Thus, delayed labor occurs when it begins later than the determinate 40 weeks. This also carries certain deadlines for the fetus: it feels trophic and oxygen deprivation. Prematurity at several weeks is determined by varying degrees of severity.

The average duration of pregnancy that is considered to be pre-term is 280 days. It is counted from the 1st day of the last menstrual period. When calculating the duration of pregnancy, the length of the menstrual cycle also plays a role.

The incidence of late delivery is 10-12%. The risk increases if the pregnant woman has neuroendocrine disorders or CNS malformations. The duration of pregnancy is quite often prolonged in first-born and multiple-born women.

Increased duration of pregnancy leads to severe complications for the fetus and the mother. Given that the fetus becomes larger in size and the central nervous system has greater maturity, this always leads to birth trauma.

How long does pregnancy last

How to calculate the duration

It is possible to determine the duration of pregnancy most accurately after ultrasound tests. With modern equipment, it is possible to determine the gestational age of the unborn child. In addition, you can determine the duration of pregnancy using the following technique: add 266 days to the day of the beginning of the last menstruation. It is worth remembering that the date obtained is only approximate. If the baby appears at any time after 37 weeks, it is already considered normal.

It is possible to determine the duration of pregnancy using different methods. Regardless of the method chosen, it is necessary to focus on the following factors:

  • cycle length;
  • sperm activity;
  • psychological and emotional state;
  • the general well-being of the woman in labor;
  • genetics.

Even after determining the approximate due date, it is worth remembering that the main task of the expectant mother remains calm anticipation and love for the future baby. To avoid unforeseen developments, you should regularly consult with your doctor, adhere to all established recommendations, undergo tests and avoid stressful situations.

Determining your due date by the date of your last menstrual period

This method of calculating the duration of pregnancy is one of the most common. You can use it only if your cycle is regular and has the same interval.

For example, if the cycle lasts on average about 35 days (for comparison, many women have a cycle of 26-28 days), then with the greatest probability of conception will occur on day 21 of the cycle, and not on day 14, as with a cycle of 28 days. Thus, the calculated term according to this methodology will be one week longer than the real obstetric duration of pregnancy.

By date of ovulation or date of conception

You can get an obstetric due date by adding two weeks to the known date of conception. Even if a woman knows the exact date of ovulation or the date of intercourse that led to conception, it does not mean that she knows the date of conception with absolute certainty. The fact is that the sperm can lead to conception for another 5 days, sometimes even longer, after entering a woman’s body.

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Meanwhile, the mature egg can be fertilized for 2 days after ovulation. At this time, it is still capable of conception. Because of this, you can not be guided by the exact date of intercourse or ovulation. After all, there is no exact guarantee that conception occurred on that particular day. The actual date of conception can be earlier or later. Therefore, the duration of pregnancy determined by this method can not be considered absolutely accurate.

How long does pregnancy last

A slightly different principle is used to calculate the duration of pregnancy if it occurred as a result of IVF. In this case, the fertilization of the egg sperm is responsible for the embryologist. Development of embryos in the laboratory lasts for 3-5 days, and then they are transferred to the uterus.

Doctors calculate the true duration of pregnancy after IVF from the date when the ovarian puncture was performed. This is one of the stages of the procedure, when the follicular fluid is taken and fertilization takes place. Two weeks are added from the date of the ovarian puncture to determine the obstetric term.

If the embryo was frozen in liquid nitrogen (this process is called cryopreservation) before being transferred into the uterus, you can only determine the exact duration of pregnancy by adding 5 days to the transfer date. To know the obstetric term, add 14 days to the obtained true duration.

How long does pregnancy last

According to the size of the uterus

When examining a woman in a gynecological chair, the doctor determines the size of the uterus with both hands. This also helps determine the approximate duration of pregnancy. This method of determination demonstrates the greatest accuracy in the early stages of pregnancy – up to about 12 weeks. The earliest term that can be determined from the size of the uterus is 5 weeks.

By this time there is a slight increase in the uterus, as well as its softening. It takes on a more round shape. At later terms, the size of the uterus may vary depending on the size of the fetus, the amount of amniotic fluid, and the pelvic structure of the expectant mother. For example, it is accepted that at 16 weeks (4 months), the bottom of the uterus is located at the middle of the distance between the pubis and the navel, at 24 weeks (6 months), the bottom of the uterus is already displaced to the level of the navel.

How long does pregnancy last


In the early term, you can determine with the greatest accuracy the duration of pregnancy. To do this, an ultrasound is performed, during which the size of the fetus egg and embryo are measured. In the first trimester a small “black circle” is determined – this is the fetal egg, followed by the emergence of the embryo. Already towards the end of the first trimester, this embryo will look like a small “band”. Also in this term its heartbeat becomes distinguishable.

More accurate is the gestational age calculated by measuring the embryo’s CRL. After 12 weeks, the term of pregnancy by ultrasound is determined by taking into account the so-called fetometry. Thus, when determining how many months the pregnancy will last, various fetal sizes are taken into account – from the length of the arms to the head.

Until the second trimester, there is proportional growth of the embryo. With this in mind, its size will be approximately identical in all women with the same gestational age. Later on, fetal sizes will vary among expectant mothers. This is absolutely normal, as it is influenced by very many factors, ranging from the weight of the mother to the age of the father of the child. In this case it is no longer possible to determine the exact duration of pregnancy with an ultrasound scan.

How long does pregnancy last

If at a long term becomes noticeable lag in the size of the fetus, most often, doctors regard this as a developmental disorder. It is usually due to the fact that the placenta does not fully transport oxygen and nutrients.

According to hCG levels in the blood

HCG is a hormone that the placenta secretes during all months of carrying the baby. It is the first hormone that signals the successful conception of the baby. Its amount gradually increases up to the 11th week, and then begins to decline gradually. In the first months, determination of hCG concentration in blood helps determine the duration of pregnancy with accuracy.

Once the tests are obtained, you should keep in mind that the lab tests for the hormone level corresponds to the due date of delivery, which is usually the fetal period. To determine the usual obstetric duration of pregnancy, you need to add 14 weeks to the date obtained.

How long does pregnancy last

Recently, urine tests to determine the duration of pregnancy are becoming particularly popular. Their principle is aimed at determining the concentration of a hormone in the urine of a pregnant woman. It is worth remembering that with the help of this test is the definition of the fetal period.

According to the fetal movement

This method of determining the term shows the least accurate results, so it is used quite rarely. It is based on the belief that women who give birth for the first time, begin to feel the first stirring of the baby around 20 weeks, and second-born women earlier – at 18 weeks. That is why many obstetricians and gynecologists recommend remembering exactly when the fetus first moved and entering this data in the exchange card.

This method of determining the duration of pregnancy often shows error. Indeed, women who are expecting a baby for the first time begin to feel fetal movements later than women who already have children. This is due only to the experience of women who can already easily identify the movement of the baby and know what sensations it is accompanied by.

Quite often, women compare the first movements of the fetus with a feeling of fluid overflow in the stomach. As a rule, the first movements are rare and irregular. Moreover, the sensitivity of the woman in labor plays a very important role here.

How long does pregnancy last

There is another nuance: slim women begin to feel the stirring faster compared to women with excess weight. If a woman in labor leads an active life and works a lot, she will feel the stirring much later. Once the due date has been determined, your doctor can calculate the approximate length of pregnancy. On average, the obstetric term is 280 days or 40 weeks.

General recommendations

In order to carry a baby without complications, it is necessary to adhere to certain recommendations:

  1. Visit your doctor regularly. If you see a doctor and attend all appointments, it will be easier for him to monitor the health of the woman in labor and the health of the baby. Be sure to share all signs and symptoms that bother you.
  2. Observe a balanced diet. During the period of childbirth, the body should receive a greater amount of various minerals and trace elements. This list includes folic acid, calcium, iron, protein and other essential nutrients. If necessary, the doctor will prescribe vitamin and mineral complexes to make up for deficiencies.
How long does pregnancy last
  1. Monitor your health status. The risk of premature birth increases in the presence of chronic diseases such as diabetes and hypertension. Therefore, it is always necessary to keep your body condition normal.
  2. Adhere to your doctor’s instructions. As soon as signs and symptoms of preterm labor are detected, the doctor immediately recommends reducing the number of working hours and spending less time. Sometimes reducing the level of physical activity is a reasonable solution.
  3. Avoid getting harmful substances in your body. The optimal solution is to quit smoking, as this will be a risk of premature birth. Alcohol and soft drugs are absolutely prohibited. You should be especially careful with prescription drugs, as well as over-the-counter medications. Before you start taking medication, it is worth consulting with your doctor.
  4. Consult with your doctor about sexual activity. This point should be skipped for those women whose pregnancy duration coincides with the previously prescribed obstetric term. Often sexual intercourse is forbidden in the case of certain complications, such as vaginal bleeding or problems with the cervix or placenta.
  5. Avoid stressful situations. The best option is to set reasonable limits and stick to them. You can improve your emotional state with meditation or by taking a yoga class. If there is a need for psychological help, you should make an appointment with a specialist.
  6. Take care of your oral health. You should brush and floss your teeth every day. Regular visits to a gynecologist are also recommended to support oral health.

If premature birth has previously occurred or if risk factors appear, the doctor may prescribe a course of progesterone injections – this will normalize the condition of the expectant mother and her baby. Thus, the normal duration of carrying a baby is 40 weeks. There are several factors that can be used to determine if the delivery is premature or delayed. There are also several techniques that are actively used in calculating the due date of the baby.

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