Health & Fitness Calculators
Pregnancy Calculator

Pregnancy Calculator

Using the due date, last period date, ultrasound date, conception date, or IVF transfer date, this calculator generates an expected pregnancy timeline.


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Table of Contents

  1. Pregnancy Length and Expected Due Date
  2. Pregnancy Confirmation
  3. Determining the due date
    1. Human Chorionic Gonadotropin (hCG) levels
    2. Ultrasound Scan
    3. Ovulation date
    4. Last menstrual period date
  4. Gestational Age Calculation Units
  5. The Specifics of Pregnancy Trimesters
    1. First Trimester
    2. Second trimester
    3. Third trimester
  6. Factors Affecting the Labor Timing
    1. Woman's age
    2. A woman's genetic predisposition
    3. Maternal health
    4. Birth order priority
    5. Multiple births
    6. Unhealthy habits and lifestyle
    7. Menstrual cycle
  7. Preterm birth
  8. Late Childbirth
  9. Determining the time of labor initiation
  10. Pregnancy Management
    1. Medications
    2. Eating Healthy
    3. Increase in Weight
    4. Staying Active

Pregnancy Calculator

The Pregnancy Calculator may predict a pregnancy timetable based on a due date, last period date, conception date, ultrasound date, or IVF transfer date.

Pregnancy Length and Expected Due Date

Pregnancy describes a woman’s status throughout the 9-month period when one or more children grow inside her. According to the World Health Organization, a typical pregnancy lasts between 37 and 42 weeks. Childbirth usually happens 38 weeks after conception or 40 weeks after the last menstrual cycle.

During the first OB-GYN appointment, the doctor offers an expected date of birth (dependent on a sonogram) or due date. A woman may also use the most recent menstrual cycle to predict the due date.

Although we can predict the due date, the actual duration of the pregnancy is determined by several variables, including age, prior pregnancy duration, and the mother’s weight at delivery. Natural variability in pregnancy lengths is still influenced by unknown factors.

According to research, less than 4% of deliveries occur on the exact due date, and 60% a week after the due date. Nearly 90% of the cases happen within two weeks of the due date.

Pregnancy Confirmation

You can confirm pregnancy using pregnancy tests or by observing a set of symptoms such as a missing menstrual cycle, elevated basal body temperature, exhaustion, nausea, and an increased rate of urine.

Pregnancy tests measure hormones that serve as biomarkers of pregnancy and include clinical blood or urine tests. They can detect pregnancy from six to eight days after fertilization.

Clinical blood tests are more accurate. They can determine the exact amount of the hCG hormone earlier and in smaller amounts. But they take longer to evaluate and are more expensive than home urine pregnancy tests.

A woman can also perform a clinical urine analysis. However, it is not always more accurate than a home pregnancy test and can be more expensive.

Determining the due date

There are several ways to determine your expected due date:

Human Chorionic Gonadotropin (hCG) levels

This hormone appears in the blood as early as two days after the implantation of the fertilized egg. The blood test allows you to know the level of hCG, but only a doctor can determine the term of pregnancy and expected delivery date by this indicator.

Ultrasound Scan

Usually, an ultrasound scan is done at 7–8 weeks of pregnancy to confirm the due date. During the ultrasound, doctors focus on the size of the fetus to determine its age.

Ovulation date

Add two weeks to the date of the last intercourse at the time of ovulation and count 40 weeks, or 280 days of pregnancy, from it. Ovulation usually occurs around 14 days after your period starts if your period is regular and has a 28-day cycle.

Last menstrual period date

This method determines your due date and the date of your upcoming delivery. It works for women who have regular menstrual cycles.

In most cases, women don't know the exact date they conceived their baby, but they can tell you exactly when their last menstrual cycle started. This is the point from which pregnancy is usually counted. For most women, the most likely time of fertilization (ovulation) is in the middle of their monthly cycle, in other words, two weeks before their next menstrual cycle begins.

Based on this date, pregnancy lasts about 280 days, or 40 weeks, from the beginning of your last menstrual cycle. Thus, you can get your estimated due date by adding 280 days to the date you started bleeding in the last cycle.

This pregnancy calculation determines the fetus's obstetric, gestational, or menstrual age. With this "calendar," doctors and nurses will track fetal development.

Gestational age differs from fetal, ovulation, or fertile age, which is two weeks less than obstetric age and is counted from the actual date of conception.

Gestational Age Calculation Units

Many people calculate gestational age in weeks. This is the easiest and most convenient way to avoid confusion. You count from the beginning of your last menstrual cycle. If your doctor says you are ten weeks pregnant, it means you conceived about eight weeks ago and will deliver in 30 weeks because the total gestational age is, on average, 40 weeks.

There is also a larger unit of measurement, the trimester. Trimesters divide pregnancy into three phases, each lasting 13 weeks.

Fetal development and the woman's well-being in these phases have particular characteristics.

The Specifics of Pregnancy Trimesters

First Trimester

In the first trimester, life is born in a woman. During half of the first trimester, the woman either does not know about her situation or can only guess if the pregnancy is planned. We can say that this trimester is the most difficult because it is an entirely new condition for a woman. It can be physically and psychologically challenging because it takes time to realize everything and get used to the new status.

Most often, the first trimester is the least comfortable for women. Because of hormonal rearrangement, your mood often changes, and there is a lot of sleepiness. Nausea is not uncommon, and some women experience severe toxicosis, up to vomiting several times a day. In the first trimester, a woman often loses a few kilos because of the lack of nutrition (familiar products cause rejection).

It is vital for a woman to rest more during this period, not to lift weights and take care of her health.

A woman's first trimester is challenging from a psychological and emotional point of view. It is related to the fact that the woman is aware of her pregnancy, and it causes considerable emotional stress even when the pregnancy is planned.

During this period, the embryo's future organs are laid down. At first, the embryo is only 2 mm in size, but the neural tube, the chord (from which the spine is formed later), and the blood vessels are laid down. Each week, the fetus grows; by the end of the first trimester, it is 6-7 cm in size and weighs about 20 g.

The placenta begins to appear from week 7. Before that, all the substances that enter the blood are also in the embryo. The woman can hear her baby's heartbeat at the first ultrasound scan.

The baby's brain is developing very intensively. The fingers and toes are separated, the urinary system is formed, and the kidneys start working at nine weeks.

By the 12th week, the fetus is already moving, though a woman may not notice it yet.

At the end of the first trimester, the first screening is done to detect possible abnormalities in the pregnancy. It combines an ultrasound scan and blood tests for specific indicators. In the first screening, several indicators are evaluated: length from vertex to coccyx (or "height"), head circumference, the thickness of the collar space, the thickness of the nasal bone, features of the brain and skull, amniotic fluid condition, uterine tone indicators.

Second trimester

In the second trimester, a woman's abdomen starts gradually growing. By about 20 weeks, the pregnancy becomes visible to others.

By the 13th week, a woman's nausea is often gone. The body gets used to its new condition. The woman's well-being is improving; her activity increases, and her anxiety decreases.

At the same time, the amount of blood circulating in the woman's body increases, and the burden on her whole body gradually increases. The woman may become constipated, so she should eat more fruits and vegetables.

By about the 20th week, the woman may begin to feel the baby's movements. By the 27th week, the baby will be about 35 cm in size and weigh like a cauliflower (about 900 g).

Already after the 13th week, the fetus activates the sucking reflex, and you can see the baby sucking a finger on the ultrasound. Internal organs continue to develop, facial expressions become more complex, and the baby starts blinking. The immune system is forming, but for now, it is entirely dependent on the mother.

By the 18th week, the fetal reproductive organs are fully formed, which means you can find out the sex of your baby.

At 19-20 weeks, the cerebral cortex formation occurs, so exposure to toxic substances such as alcohol and nicotine is hazardous at this stage.

If preterm birth occurs after 22 weeks, the fetus may survive because its lungs are already sufficiently formed. But such a baby will have serious health problems.

Third trimester

Active weight gain begins in the woman and the fetus in the third trimester. The woman's belly grows rapidly.

In the third trimester, the future mother's activity and level of well-being decrease. Most pregnant women complain about the worsening of their well-being. The woman's anxiety level increases. It is related to fear of pain and fear of childbirth. But overall, the mood of the expectant mother remains positive because she feels the joy of waiting to meet her baby.

Every week a woman gains 300-350 grams, sometimes even more, because she wants to eat a lot. Because of the enlarging belly, it becomes difficult for her to sleep at night and it becomes uncomfortable for her to move around.

The baby is actively growing, and the mother's load on all organs increases. Pregnant women feel the urge to go to the bathroom more often. Some women experience a lack of oxygen and lower back pain.

At 38 weeks, the pregnancy is considered full-term, but the baby can be born at 42 weeks and it is also considered normal.

The baby begins to taste and may respond to what his mother eats. Milk teeth inside the gums are being set. The immune system continues to develop. By 33 weeks, the internal organs are fully formed. After that, the baby is already mostly accumulating subcutaneous fat to gain mass.

After 30 weeks, the baby usually occupies the specific position in which they come into the world. The correct position is the head-down position. But sometimes, this does not happen, and the baby stays in the breech position. The abdomen becomes tighter, the baby's movements become less active but intensely palpable, and the mother can discern a bump with her hand or foot.

By 38 weeks, the baby looks like a newborn and weighs about 3 kg. The baby will weigh 2.5–4 kg by the time they are born.

Factors Affecting the Labor Timing

Delivery from 37 weeks to 42 weeks is considered normal. Anything earlier than this is considered premature and abnormal.

The most common factors that affect labor time are:

Woman's age

Women under the age of 20 and women over 36 can give birth earlier or with a slight delay.

A woman's genetic predisposition

If the mothers and grandmothers of the currently pregnant woman gave birth earlier than expected, she might also give birth earlier than indicated in the chart.

Maternal health

A history of chronic illness increases the chances of preterm birth.

Birth order priority

First-time mothers are more likely to give birth late. This is due to the long process of preparing the body for this process. The greater the mother's experience with childbirth, the greater the likelihood of an early delivery.

Multiple births

Two or three fetuses put more pressure on the internal pharynx of the uterus. The more pressure, the sooner labor will begin. Often, multiple births occur before 39 weeks.

Unhealthy habits and lifestyle

Moms with bad habits, according to statistics, give birth earlier than expected. Women with increased body weight and minimal physical activity are prone to over-birth.

Menstrual cycle

If a woman's menstrual cycle is less than 28 days, there is a high chance of early delivery by 7–14 days. With a long cycle, she can give birth at 42 weeks.

Preterm birth

Preterm labor is a labor process that begins between 22 weeks of pregnancy and 37 weeks.

The clinical picture of early labor is not much different from normal delivery. First, a woman begins to have tugging pains in the lower abdomen and lower back. Then contractions appear. Labor activity may be sluggish or strong. Water breakage may occur. Sometimes there is bloody discharge, indicating a detached placenta.

Predisposing factors for preterm birth are:

  • Young age;
  • Bad habits;
  • Abortions;
  • Miscarriages;
  • Urogenital infections;
  • Severe somatic diseases;
  • Pregnancy complications
  • Severe stress.

Late Childbirth

Late labor is quite common. Up to 42 weeks of pregnancy is considered normal. The causes of late delivery are:

  • An error in the established timing;
  • A large fetus (more than 4 kilograms);
  • Hormonal imbalances;
  • Sedentary lifestyle;
  • Threats of miscarriage.

Determining the time of labor initiation

There are so-called harbingers of labor. These include:

  • Abdominal prolapse;
  • A week before labor, the mucus plug falls away;
  • A week before labor, the body weight drops;
  • Before labor, the stool becomes liquid and frequent;
  • Tensive pain in the lower abdomen and lower back may occur;
  • The amniotic fluid retreats
  • Сontractions every 4 minutes.

If the interval between contractions is 4 minutes, it is recommended to go to the hospital.

Pregnancy Management

Several elements must be addressed during pregnancy, depending on the individual’s condition, such as medication, weight gain, activity, and diet.


Certain medications can have long-term consequences for the baby if used during pregnancy. The Food and Drug Administration (FDA) categorizes medications in the United States into classes A, B, C, D, and X based on potential benefits vs. fetal dangers. A pregnant woman should discuss any medications she plans to take during her pregnancy with her doctor.

Eating Healthy

Nutrition is crucial during pregnancy for the health of both the mother and the baby. Because of the increased energy and particular micronutrient demands, pregnancy causes different dietary choices than when not pregnant.

There is a lot of different information about what pregnant women should eat and what they should avoid. Specific vitamins, such as folic acid, can help reduce the risk of certain defects. Other nutrients, such as DHA Omega-3, required for proper brain and retinal growth, cannot be created effectively by infants and can only be gained through the placenta during pregnancy or in breast milk after birth.

The information might be challenging and differ from person to person. Therefore, pregnant women should contact their doctors and dieticians to identify the best strategy for their requirements.

Increase in Weight

Weight gain is an essential component of pregnancy that differs from person to person. It influences fetal growth, including the baby’s weight, the placenta, extracellular fluid, and fat and protein storage.

Weight control is necessary because insufficient or excessive weight gain can harm both the mother and the fetus. For example, it can lead to the need for a cesarean section (C-section) and gestational hypertension.

The Institute of Medicine recommends an expected pregnancy weight gain of

  • 28-40 lbs. for underweight women (BMI <18.5)
  • 25-35 lbs. for “normal” weight women (BMI between 18.5-24.9)
  • 15-25 lbs. for overweight women (BMI 25-29.9)
  • 11-20 lbs. for obese women (BMI > 30)

Therefore, we recommend using our Pregnancy Weight Gain Calculator since it is derived from the Institute of Medicine recommendations.

Staying Active

According to research, aerobic activity during pregnancy helps increase or maintain good health while possibly lowering the likelihood of C-sections. Therefore, experts usually recommend pregnant women do regular aerobic and strength exercises.

Women who exercised regularly before pregnancy and had uncomplicated pregnancies can continue their high-intensity workouts. Per the American College of Obstetricians and Gynecologists (ACOG), fetal damage due to exercise is rare in an uncomplicated pregnancy.

Pregnant women should be careful and seek advice from their doctor if they experience any of the following symptoms: vaginal bleeding, shortness of breath, lightheadedness, headache, calf pain or swelling, amniotic fluid leakage, lessened fetal movement, preterm labor, muscle weakness, or chest pain.