A pregnancy that lasts more than 42 weeks is called post-term. A pregnancy that is between 41 and 42 weeks is called late-term. Most women deliver between 37 and 42 weeks of pregnancy.
Doctors do not know why some women carry a pregnancy longer than others. It is often because of miscalculating the due date. You are also more likely to have a post-term pregnancy if you:
- Are pregnant with your first baby
- Had past pregnancies that went past 42 weeks
- Are overweight
- Are having a boy
There are no symptoms of a post-term pregnancy.
To calculate you due date, your healthcare provider will:
- Measure the size of your uterus at certain points in early pregnancy
- Note the date he or she first hears your developing baby's heartbeat
- Note when you first feel your baby moving in your uterus
- Use ultrasound
In a post-term pregnancy, your healthcare provider may do testing to check on your baby's well-being and for problems. Tests may include:
- Seeing how your baby's heart rate responds to activity
- Checking the amount of amniotic fluid
The goal is to prevent problems and deliver a healthy baby. Your healthcare provider will base specific treatment on:
- Your pregnancy, your overall health, and your health history
- How well you can handle specific medicines, procedures, or therapies
- Your opinion or preferences
Your healthcare provider may do maternal and fetal testing to watch for problems. Tests include:
- Fetal movement counting. This keeps track of your baby's kicks and movements. A change in the number or frequency may mean the developing baby is under stress.
- Non-stress testing. This test watches how your baby's heart rate for increases with your baby's movements. This is a sign of your baby's well-being.
- Biophysical profile. This test combines the non-stress test with an ultrasound to look at your baby's well-being.
- Ultrasound. This test uses high-frequency sound waves and a computer to make images of blood vessels, tissues, and organs. Ultrasounds are also used to follow the growth of your developing baby.
- Doppler flow studies. This is a type of ultrasound that uses sound waves to measure blood flow. The test is commonly used if a developing baby is not growing properly.
If tests find that it is not healthy for the developing baby to stay in your uterus, your healthcare provider may induce labor to deliver the baby.
The decision to induce labor depends on many things. During labor, your provider may monitor your baby's heart rate with an electronic monitor. This is done to watch for changes in the heart rate caused by low oxygen levels. You may need a cesarean delivery if your baby's condition changes.
Amnioinfusion is sometimes used during labor if there is very little amniotic fluid or if the baby is pressing on the umbilical cord. A sterile fluid is put into the uterus with a hollow tube (catheter). The fluid helps replace the amniotic fluid and cushions the baby and cord.
Women with post-term pregnancy, especially with a large baby, are more likely to have:
- Longer labor
- Forceps or vacuum-assisted birth
- Vaginal tearing or injury
- Cesarean delivery
- Infection, wound complications, and bleeding after birth
There are also risks for the fetus and newborn in a post-term pregnancy. These include:
- Stillbirth and newborn death
- Placenta problems
- Decreased amniotic fluid
- The fetus may stop gaining weight, or may even lose weight
- Birth injury if the baby is large
- Baby breathes in fluid containing the first stool (meconium aspiration)
- Low blood sugar (hypoglycemia) because the baby has too little glucose stored
Once your pregnancy has reached 37 weeks, you will have weekly appointments with your healthcare provider. If your pregnancy goes past 41 weeks, you and your healthcare provider will talk about your options. You will also decide how often you need to be seen to check your pregnancy and the health of your baby. It is important to keep all of your appointments.
Contact your healthcare provider right away if:
- Your membranes rupture and amniotic fluid comes out
- You have bleeding
- You notice a change in your baby's activity level
- A pregnancy that lasts more than 42 weeks is called post-term.
- Doctors do not know why some women carry a pregnancy longer than others.
- You may need tests to watch for signs of problems.
- If tests find that it is no longer healthy for your baby to stay in your uterus, your healthcare provider may induce labor to deliver the baby.
Tips to help you get the most from a visit to your healthcare provider:
- Know the reason for your visit and what you want to happen.
- Before your visit, write down questions you want answered.
- Bring someone with you to help you ask questions and remember what your provider tells you.
- At the visit, write down the name of a new diagnosis, and any new medicines, treatments, or tests. Also write down any new instructions your provider gives you.
- Know why a new medicine or treatment is prescribed, and how it will help you. Also know what the side effects are.
- Ask if your condition can be treated in other ways.
- Know why a test or procedure is recommended and what the results could mean.
- Know what to expect if you do not take the medicine or have the test or procedure.
- If you have a follow-up appointment, write down the date, time, and purpose for that visit.
- Know how you can contact your provider if you have questions.
January 16, 2018
What to Expect After Your Due Date. The American College of Obstetrics and Gynecologists. http://www.acog.org/~/media/For%20Patients/faq069.pdf?dmc=1&ts=20130521T1524296499, Postterm Pregnancy. Porter Robert S. 2011;19:2681., Postterm Pregnancy. UpToDate.
Freeborn, Donna, PhD, CNM, FNP ,Bowers, Nancy, RN, BSN, MPH