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Pregnancy and birth: When your baby’s due date has passed

Created: ; Last Update: March 22, 2018; Next update: 2021.

The last few days of pregnancy are an exciting time. But when your due date has passed, waiting for labor to start can be stressful too. Many parents-to-be become anxious. If there are no specific problems, the baby is very probably doing fine, though.

When a pregnancy continues its full normal course (about 40 weeks), it is called a term pregnancy or full-term pregnancy. If a baby is born before 37 completed weeks of pregnancy, it is considered to be a preterm birth. Being born too early is associated with various risks for the baby. A pregnancy that continues for longer than 42 weeks is called a post-term, prolonged or overdue pregnancy. This definition may vary from country to country.

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.

The reason why the baby is overdue is usually not known. Sometimes it is because of a genetic predisposition (hereditary). Women who have already had a baby that came much later than their due date are more likely to have an overdue baby in future pregnancies.

Being born after the 40th week only rarely harms the child. To be on the safe side, though, the doctor or midwife will start doing more checks to see how she or he is doing.

Is a longer pregnancy a problem?

In the first week after the due date, the baby and mother are not at higher risk of complications if they are both doing well. Even after that, the risk of something happening to the baby doesn't increase much. But certain risks do increase a little. If a baby is overdue, the main associated risks are:

  • The placenta might gradually stop being able to do its job properly.
  • An infection might develop inside the womb.
  • Unexpected problems might arise during labor.

Being overdue is generally associated with few risks for the pregnant woman. But childbirth can be more difficult if the child is too big.

Almost all babies are born within three or four weeks of the due date. If a baby hasn't been born by then, the risk of being stillborn (dead at birth) increases. Babies are very rarely born that late, though, because labor is usually induced two weeks after the due date at the latest.

To induce labor, hormones or other methods are used to try to get labor (contractions) started artificially.

How is the baby’s due date calculated?

It's important to know the approximate due date because a lot of decisions are based upon this estimate. For instance, the due date is important for determining when maternity leave starts, and deciding whether to induce labor or do additional examinations. But the baby’s due date or “estimated date of delivery” (EDD) is never absolutely accurate.

There are two main ways to estimate how far along a pregnancy is: calculating the due date based on the last menstrual period, and trying to determine the unborn baby’s age by doing ultrasound scans to see how big he or she is.

Calculating the due date based on the last menstrual period

The length of pregnancy is always considered to be 40 weeks (or 280 days) – even though very few pregnancies last exactly 280 days. The starting date for these 40 weeks is the first day of your last menstrual period. But this estimate isn't very reliable because women don't always remember exactly what day that was. And some women still have light bleeding at the start of pregnancy, around the time when they would normally have got their period. So they might have been pregnant for a few weeks longer than they realize.

What's more, periods aren't always exactly four weeks apart. And the baby might have been conceived a little later after your period than assumed in the calculation. These are further factors that make it harder to calculate an accurate due date.

Due to frequent mistakes in estimating when the pregnancy started, doctors and midwives sometimes adjust due dates that were calculated in this way – for instance, based on the size of the child in an ultrasound scan during early pregnancy.

Calculating the due date based on an ultrasound scan

Ultrasound (also called ultrasonography) involves the use of sound waves that bounce off the baby’s body and are turned into an image. This makes it possible to see what is happening inside the womb (uterus), and how big the baby is. The size of the baby can be used to estimate how old the unborn baby is. This estimated age, known as the gestational age, tells us how many weeks the woman has been pregnant.

In the first few weeks of pregnancy, developing babies (embryos) are very similar in size. This means that the due date can be estimated quite accurately based on ultrasound scans in the first trimester (the first twelve weeks) of pregnancy. But ultrasound scans aren't entirely accurate either.

In Germany, women are usually offered an ultrasound scan between eight and twelve weeks of pregnancy. If the estimated due date based on the ultrasound scan is very different to the due date calculated based on your last period, your doctor or midwife can adjust your due date accordingly.

How can you see how the unborn baby is doing?

Certain examinations can help midwives and doctors to identify possible problems affecting the mother or child. If your due date has passed, you are likely to be offered more appointments and check-ups. In Germany, women who have passed their due date usually have check-ups twice a week.

Common examinations include cardiotocography (CTG, also called a non-stress test) and ultrasound scans. The CTG is used to monitor the baby’s heart rate. The ultrasound scan is used to check the baby’s size and the amount of amniotic fluid around the baby. You might also be checked for signs of infection, especially if amniotic fluid has been leaking. Other tests are sometimes used to determine what is known as the baby’s “biophysical profile.” For example, one of these tests involves counting his or her movements.

Most overdue babies are still usually born without any complications. To lower the risk of complications, it is common to suggest inducing labor after a certain amount of time has passed, even if the mother and baby are doing well.

When is labor induced?

Whether and – if so – when labor is induced is a personal decision that parents-to-be can make together with their doctors. It will mainly depend on whether there is a high risk of complications during the birth. The critical factors include

  • how much overdue the baby is,
  • how old the woman is,
  • whether she has already given birth to another child,
  • whether she smokes,
  • how much she weighs,
  • how big the child is, and
  • whether there are any signs that the child is in danger.

Doctors usually suggest inducing labor if there are signs of possible complications that mean the baby needs to be born soon – but the complications aren't serious enough for the baby to be delivered by Cesarean.

Even if there are no signs of complications, labor induction will probably be recommended after a certain amount of time anyway.

If one week has passed since the due date, inducing labor can lower the risk of the baby dying. But this risk is generally very low: it happens in about 3 out of 1,000 births when labor isn't induced. Inducing labor can also lower the risk of serious breathing problems and of having to have a Cesarean section.

What can you do yourself to get labor started?

There are many traditional methods that women use to try to get labor started, including things like going on long walks. Some women try to induce labor by having sex or stimulating their nipples. These approaches are based on the theories that hormones in men’s semen (the sperm-carrying fluid that is released during ejaculation), and hormones that women’s bodies make when sexually aroused, cause the pregnant woman’s cervix to relax and open more easily.

There has even been research on these approaches. But it only produced weak evidence suggesting that stimulating nipples for about one to three hours per day can help. This is what was found:

  • Without stimulation: In about 8 out of 100 women who did not stimulate their nipples, labor started within 72 hours.
  • With stimulation: This was the case in about 39 out of 100 women who stimulated their nipples.

Because only about 400 women took part in the studies, these findings can only give us a rough idea of how effective nipple stimulation might be in other women.

Nipple stimulation also reduced the risk of bleeding after giving birth. But nipple stimulation was only found to be effective in women who did not have any major problems in pregnancy. Research has not found that sex induces labor.

Women sometimes try out a number of other things to try to get childbirth started. Some drink raspberry leaf tea to soften the cervix, while others use homoeopathy, evening primrose oil, acupuncture, or hypnosis. But there is no scientific proof that these approaches work.

Castor oil is another traditional method used to try to induce labor. It is available in the form of a juice, a solution used in colonic irrigation, or capsules that are swallowed. This oil has not been proven to have a positive effect. But research has shown that it causes nausea in most women. There is not enough research on the safety and effectiveness of castor oil.

How is labor medically induced?

There are several different methods that doctors commonly use to induce labor. One of the first steps is often to prepare the cervix for birth. The cervix is the opening or “neck” of the womb. It is tightly closed throughout the pregnancy. When the body starts preparing for birth, hormones make the cervix relax and become softer. A cervix that is ready for labor is sometimes called a “ripe” cervix. Hormones, especially hormones called prostaglandins, may be applied to the cervix in the form of a gel to prepare it for birth. They can also be used to induce labor contractions. Balloon catheters are sometimes used to stretch and open the cervix as well.

Sometimes these measures are enough to set the birth off. If not, other hormones are used – typically either prostaglandins or oxytocin. These drugs can be swallowed, inserted into the vagina in the form of tablets or suppositories, or “fed” into a vein in your arm using an infusion (an IV drip).

When labor contractions start, the amniotic sac can also be opened (“the water broken”) to help things along. The amniotic sac is the fluid-filled bag that the baby is inside. It can be opened by making a small, painless cut – a procedure known as amniotomy. Sometimes labor can also be induced with the help of a “membrane sweep.” This is where the membranes of the sac surrounding the baby are gently separated from the wall of the womb using a finger. Although these procedures don't usually hurt, most women find them unpleasant.

Once a woman’s water breaks, the amniotic sac can't be closed again. So it's important that labor starts quite soon afterwards, because the baby is no longer protected by the amniotic fluid.

Induced labor doesn't cause any serious problems in most women. But they might have side effects. The main side effects of prostaglandins are gastrointestinal problems like nausea, vomiting and diarrhea. Oxytocin can cause water retention and other problems involving fluid balance, such as low sodium levels.

The amount of hormones in the IV drip is adjusted to make the induced contractions as normal as possible – in other words, not too frequent and not too strong. Induced labor should not force a birth, but help it happen as naturally as possible.

What does induced labor feel like?

When labor is induced, more tests are needed than usual. Although these might be unpleasant, overall most women don't find this or other aspects of labor induction particularly distressing. The relief of finally being able to give birth to their child often overrides other feelings.

Some women worry that the pain associated with an induced labor might be worse than the pain associated with labor that starts on its own. But most women who are induced don't report a great deal more pain than women who have spontaneous births. In some studies, women were asked how they feel about having been induced. Most of them responded that they would do it again. Inducing labor doesn't necessarily mean that everything will happen really quickly either: Many women are surprised by how long it takes from the start of induction until the baby is born.

It can be helpful to ask your midwife or doctor about the options for inducing labor in your hospital, and about the associated advantages and disadvantages. Induction of labor isn't an emergency – there is usually enough time to get used to the idea and have all your questions answered.


© IQWiG (Institute for Quality and Efficiency in Health Care)
Bookshelf ID: NBK279571


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