How Long Is My Pregnancy

What Week Is Normal For Delivery

About 60 out of 100 women give birth on or before their given due date. In another 35 out of 100 women, contractions start on their own within two weeks of the due date. But it takes longer in about 5 out of 100 women.

Its impossible to answer that big question how long is pregnancy with exact certainty, but a baby who is between 37 and 42 weeks gestation is considered term. There are, however, some nuances youll want to know about:

• A baby born between 37 weeks and 38 weeks 6 days is considered early term
• A baby born between 39 weeks and 40 weeks 6 days is considered full term
• A baby born during the 41st week of pregnancy is considered late term
• And a baby born 42 weeks or later is considered post term

By 37 weeks, it is generally safe to deliver baby if you go into labor. By this time, baby is fully formed, and has begun to move down into the pelvis in preparation for birth. Many midwives need babies to be at least 36 weeks, if not 37 weeks, to do a home birth.

However, unless there is a significant medical reason to do so, newer recommendations say induction and C-sections should not happen before baby reaches full term. Research shows that babies born at 37 weeks have more of a risk of complications, such as difficulty breathing, than those born just two weeks later.

Is It Possible For My Due Date To Change

Typically, an ultrasound is used to confirm your due date , and once a due date has been selected, it does not change no matter how many additional ultrasound exams you may have during your pregnancy, states ACOG.

Still, ACOG also notes that subsequent changes to the EDD should be reserved for rare circumstances, discussed with the patient and documented clearly in the medical record. A pregnancy without an ultrasound examination that confirms or revises the EDD before 22 0/7 weeks of gestational age should be considered suboptimally dated.

Why Pregnancy Is Counted From The Last Menstrual Period

Pregnancy is counted from a women’s last menstrual period because the start of a period is easily observable and usually known to a woman whereas the date of conception is much less likely to be known.

Historically, the first day of the last menstrual period became the date from which pregnancy is counted even though conception occurs about two weeks later.

The LMP formula is good for working out an initial age of pregnancy but ultrasound is more accurate. The age of pregnancy may be revised following your ultrasound scan.

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How Accurate Are Due Dates

In short, due dates are not very accurate. In fact, only about 4% of women will give birth on their due date. Note that due dates are not expiration dates! Most first-time moms will give birth 3-5 days past their due date, and a great many go longer than that still.

Going past your due date can be frustrating. Your provider will discuss all of your options, like waiting for labor to start on its own versus scheduling an induction with you.

Ultimately, due dates are really exciting to think aboutbut my recommendation is to try to think of them as an approximation. Instead of saying, “I’m due on May 15th,” maybe try, “I’m due sometime in May!”

Mama, your baby will come, and when they do, it will be the most perfect date of all: Your baby’s birthday!

Missed Period During Early Pregnancy

Once implantation is complete, your body will begin making human chorionic gonadotropin . This hormone helps the body maintain the pregnancy. It also tells the ovaries to stop releasing mature eggs each month.

You will likely miss your next period 4 weeks after conception. If you typically have an irregular period, youll want to take a pregnancy test to confirm.

Most home tests can detect hCG as soon as 8 days after a missed period. A pregnancy test will be able to detect hCG levels in your urine and show if you are pregnant.

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What Is My Due Date

Your due date, also known as your estimated date of delivery, is the approximate date your labor might begin. Your estimated due date is commonly calculated by adding 280 days to the date of the first day of your last period, using Naegeles rule.1This may vary if you have irregular periods.

It’s worth noting that although predicted due dates are commonly calculated at 280 days, a baby is born on its predicted due date just 5% of the time.2 A 2020 study published in the International Journal of Obstetrics & Gynaecology suggests a number of factors that can influence the length of your pregnancy, including ethnicity, height, variations in the menstrual cycle, the timing of ovulation, parity and maternal weight. It is for this reason that calculations using Naegeles rule can be considered as an estimate and not a definitive date.3

Dating Pregnancy Using Ultrasound

Ultrasound in the first trimester is the most accurate method of dating pregnancy. During the scan, baby is measured and the age of pregnancy is estimated by comparing baby’s size against recorded averages. If there is a significant difference between gestational age according to LMP and gestational age according to the ultrasound, you may be given a new gestational age and due date based on the ultrasound measurements.

Your pregnancy may also be dated by ultrasound measurement if an LMP formula was not appropriate for your pregnancy for any reason. LMP formulas are not suitable in several situations including the following: LMP is not known or is not certain, birth control pills were taken in the two months before LMP, the menstrual cycle is irregular, you are carrying multiples .

Although the age of pregnancy based on ultrasound measurements is more accurate than the age of pregnancy based on LMP, both are estimates and not definitive statements.

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How Is Pregnancy Due Date Calculated

Your pregnancy due date is calculated by adding 40 weeks to the first day of your last menstrual period . This is done with an assumption that you have a 28-day menstrual cycle. The time between your menstrual period and ovulation is calculated as the first two weeks of pregnancy, as ovulation takes place two weeks after the first day of LMP. If you deliver the baby on the estimated due date, she is 38 weeks old after conception and not 40 .

If you miss your first period, you are likely to be four weeks pregnant .

What If I Have Irregular Periods Or Long Cycles

Some women have cycles that are consistently longer than the average 28-day cycle. In these cases, a pregnancy wheel can still be used, but some simple calculations are necessary.

The second half of a womans menstrual cycle always lasts for 14 days. This is the time from ovulation to the next menstrual period. If your cycle is 35 days long, for example, then you probably ovulated on day 21.

Once you have a general idea of when you ovulated, you can use an adjusted LMP to find your due date with a pregnancy wheel.

For example, if your menstrual cycle is usually 35 days long and the first day of your LMP was November 1:

After you calculate your adjusted LMP date, simply mark it on the pregnancy wheel and then look at the date where the line crosses. That is your estimated due date.

Some pregnancy wheels may allow you to enter the date of conception which occurs within 72 hours of ovulation instead of the date of your LMP.

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How Do I Know What Week I Am Currently In My Pregnancy

Your doctor says you’re 15 weeks pregnant, but youre also being told that youre in week 16. Which is right? Short answer: both. In both cases, your due date is the same its the language referring to it thats different.

Turns out how many weeks into pregnancy you are is a little different than how many weeks pregnant you are. If youre in week 16, youre actually 15 weeks and some days pregnant. Fifteen full weeks have gone by, but not 16 weeks, so people say that you’re both 15 weeks pregnant and in week 16 of pregnancy.

To clear things up, think about birthdays. When you were born, you werent even a day old but you were in your first week of life. When you turned 1 year old, you had lived through your first year and were starting on your second. In other words, on your first birthday you were in day one of your second year. But no one said you were 2 years old until you’d finished that second year and had begun your third.

The same rules apply when talking about your weeks of pregnancy: You are x weeks pregnant, but in your x+1 week of pregnancy.

Pregnancy Week 4 Fetal Development

During this important phase of your pregnancy, the embryo grows and develops within the lining of the uterus. The outer cells form links with your blood supply, while the inner cells form 3 separate layers:

• The inner layer becomes the lungs, stomach, gastrointestinal system, and bladder.
• The middle layer becomes the heart, blood vessels, muscles, and bones.
• The outer layer becomes the brain and nervous system .

During the first part of this stage of pregnancy, the embryo draws nourishment from a small yolk sac. Soon afterwards, the placenta that develops from the outer layer of the amniotic sac that surrounds the embryo takes over this role of providing sustenance to your growing baby.

During this period, the beginning of a face starts to form: this includes large, dark circles for eyes, and a mouth, lower jaw, and throat. Blood cells start to form and the circulation begins.

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When Should I Call My Doctor

A note from Cleveland Clinic

A due date calculator helps you plan for your babys arrival. Keep in mind that a due date calculator is only an estimate. Youll need to see your provider to confirm the date. Your due date may change when you have a prenatal ultrasound. Your provider may even change your due date more than once during your pregnancy, but it usually only changes by a few days. Knowing when to expect your new family member allows you to prepare mentally and physically. An accurate due date also helps your provider monitor your health and the health of your baby.

Last reviewed by a Cleveland Clinic medical professional on 10/07/2021.

References

How Accurate Is The Due Date Calculator

No estimated due date is ever 100% accurate, and even ultrasound scans arent entirely accurate. However, the ACOG notes that the most accurate method of confirming gestational age is an ultrasound measurement of the fetus or embryo in the first trimester, citing an accuracy of +5-7 days.

Find a Pediatrician Near You

Zocdoc helps you find and book top-rated doctors, on demand. Visit them in their offices, or video chat with them from home. Check out the Pediatricians in your area.

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How Long Is A Cat Pregnant For

Cat pregnancies typically last between 63 and 67 days, however, the exact duration of a cats pregnancy is difficult to determine. Cats can have gestation periods ranging from 61 to 72 days.

For the first few weeks of her pregnancy, your cat may not show any visible signs of her pregnancy. Consult your veterinarian if you have any suspicions that your cat might be pregnant.

Its possible to identify whether or not your cat is pregnant by looking at its physical characteristics after two or three weeks.

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When Is My Due Date

There are a few ways to calculate your due date. The first is based on the first day of your last menstrual period . Here is the formula:

• Write down the first day of your last LMP
• Subtract three months

So, say your LMP was on April 10th:

• Subtracting three months from April brings you to January.
• Adding seven days to 10 gives you 17.
• Your due date will be January 17th.

You can also use a due date calculator, which can also help if you know the day of intercourse, insemination or embryo transfer, or try our handy graphic below.

Related:

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What To Expect During The Second Trimester

During the second trimester, your healthcare provider may recommend or want to run the following tests:

• Triple screen/Quad screen
• Anatomy ultrasound
• CBC blood tests

The tests are performed in order to detect neural tube defects, Down Syndrome, spina bifida, anencephaly, and more. Some of these tests are standard like the anatomy ultrasound where you get to check out all of babys development and discover your babys sex! Others, such as amniocentesis, have a very high level of risk and should be discussed with your doctor. For a full list of these tests, how theyll be done, why theyre performed, and if theyre mandatory, read my article about second trimester tests.

How To Calculate Weeks Of Pregnancy

Pregnancy is calculated based on your last menstrual period. Week one of your pregnancy will start on the first day of your LMP. Likewise, the following weeks are calculated. This may sound weird, but it helps in giving the exact date for timely medical care. Unless you had an assisted conception and knew when the fertilization took place, the LMP method is the only way to know the closest ovulation and conception dates.

The doctors can help you with the exact calculation of weeks and months of pregnancy through other ways.

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Average Length Of Pregnancy

While 40 weeks is the average, its not unusual to deliver your baby earlier or later. In the past, 37 weeks was considered to be a full-term pregnancy. This definition carried implications on as two when it would be safe to induce labor or schedule a cesarean section.

However, we now know that being born at 37 weeks can increase health risks. Its not nearly as risky as being born before 37 weeks, but its not ideal either.

In response, the American College of Obstetricians and Gynecologists has created new definitions to describe the timing of labor:

Frequently Asked Questionsexpand All

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How Long Are Dogs Pregnant

According to PetMD, dogs are pregnant for about 63 days or a little over two months from the time of ovulation. If the ovulation timing is unknown or cannot be determined, the due date may range from 58-68 days from the day of breeding.

Its advisable to get your dog checked by a vet to determine the ovulation timing and overall health to see if its fit for pregnancy before going further.

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How Many Weeks Is A Full

If you’re carrying a single baby, a full-term pregnancy is between the start of 39 weeks up to the end of 40 weeks. If you’re carrying twins, a full-term pregnancy is considered at least 38 weeks.

The American College of Obstetricians and Gynecologists as outlined the following terms for pregnancy, depending on when your baby is born:

• Preterm: 20 weeks to 37 weeks
• Early term: 37 weeks 0 days to 38 weeks 6 days
• Full term: 39 weeks 0 days to 40 weeks 6 days
• Late term: 41 weeks 0 days to 41 weeks 6 days
• Post term: after 42 weeks 0 days

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Best Time Of Day To Test

Youre more likely to get an accurate result if you take the test in the morning. This is especially true if your period is not yet late, or if your period is only a couple of days late.

Your urine is usually more concentrated when you first wake up. This generally means that the amount of hCG is a bit higher, and youre more likely to get a positive result if youre pregnant.

However, you can still take a pregnancy test at a different time of day. Youre just more likely to get a false negative, especially if youve been drinking a lot of water and your urine is diluted.