Postterm pregnancy

Postterm pregnancy
Synonyms post-term, postmaturity, prolonged pregnancy, post-dates pregnancy, postmature birth
Classification and external resources
Specialty pediatrics
ICD-10 O48, P08.2
ICD-9-CM 766.22
DiseasesDB 10417
eMedicine med/3248
MeSH D007233

Postterm pregnancy is the condition of a baby that has not yet been born after 42 weeks of gestation, two weeks beyond the normal 40.[1] Post-mature births can carry risks for both the mother and the infant, including fetal malnutrition. After the 42nd week of gestation, the placenta, which supplies the baby with nutrients and oxygen from the mother, starts aging and will eventually fail. If the fetus passes its fecal matter, which is not typical until after birth, and breathes it in, it could become sick with meconium aspiration syndrome. Postterm pregnancy may be a reason to induce labor.[2]

Signs and symptoms

Postmaturity symptoms vary. The most common are dry skin, overgrown nails, creases on the baby's palms and soles of their feet, minimal fat, a lot of hair on their head, and either a brown, green, or yellow discoloration of their skin. Doctors diagnose post-mature birth based on the baby's physical appearance and the length of the mother's pregnancy.[3] Some postmature babies will show no or little sign of postmaturity.

Fetal and neonatal risks

Maternal risks


The causes of post-term births are unknown, but post-mature births are more likely when the mother has experienced a previous post-mature birth. Due dates are easily miscalculated when the mother is unsure of her last menstrual period. When there is a miscalculation, the baby could be delivered before or after the expected due date.[6] Post-mature births can also be attributed to irregular menstrual cycles. When the menstrual period is irregular it is very difficult to judge when the ovaries would be available for fertilization and subsequent pregnancy. Some post-mature pregnancies are because the mother is not certain of her last period, so in reality the baby is not technically post-mature.[2] However, in most countries where gestation is measured by ultrasound scan technology, this is less likely.


Once a baby is diagnosed post-mature, the mother should be offered additional monitoring as this can provide valuable clues that the baby's health is being maintained.

Fetal movement recording

Regular movements of the baby is the best sign indicating that it is still in good health. The mother should keep a "kick-chart" to record the movements of her baby. Less than 10 movements in 2 hours is not a good sign, and a doctor should be contacted. If there is a reduction in the number of movements it could indicate placental deterioration.

Electronic fetal monitoring

Electronic fetal monitoring uses a cardiotocograph to check the baby's heartbeat and is typically monitored over a 30-minute period. If the heartbeat proves to be normal, the doctor will not usually suggest induced labor.

Ultrasound scan

An ultrasound scan evaluates the amount of amniotic fluid around the baby. If the placenta is deteriorating, then the amount of fluid will be low, and induced labor is highly recommended. However, ultra sounds are not always accurate since they also monitor the fetus's development, and if the fetus is smaller than normal, the doctor's guess at the age can be quite off. The actual placenta won't start to deteriorate until about 48 weeks. Because of the risks, doctors favour induction by 42 weeks.

Biophysical profile

A biophysical profile checks for the baby's heart rate, muscle tone, movement, breathing, and the amount of amniotic fluid surrounding the baby.

Doppler flow study

Doppler flow study is a type of ultrasound that measures the amount of blood flowing in and out of the placenta.[5]



A woman who has reached 42 weeks of pregnancy is likely to be offered induction of labour. Alternatively, she can choose expectant management, that is, she waits for the natural onset of labour. Women opting for expectant management may also choose to carry on with additional monitoring of their baby, with regular CTG, ultrasound, and biophysical profile. Risks of expectant management vary between studies.[7]

Inducing labor

Main article: Labor induction

Inducing labor is artificially starting the labor process by using medication and other techniques. Labor is usually only induced if there is potential danger on the mother or child.[8] There are several reasons for labor induction; the mother's water breaks, and contractions have not started, the child is post-mature, the mother has diabetes or high blood pressure, or there is not enough amniotic fluid around the baby.[9] Labor induction is not always the best choice because it has its own risks. Sometimes mothers will request to be induced for reasons that are not medical. This is called an elective induction. Doctors try to avoid inducing labor unless it is completely necessary.[8]


There are four common methods of starting contractions. The four most common are stripping the membranes, breaking the mother's water, giving the hormone prostaglandin, and giving the synthetic hormone pitocin. Stripping the membranes doesn't work for all women, but can for most. A doctor inserts a finger into the mother's cervix and moves it around to separate the membrane connecting the amniotic sac, which houses the baby, from the walls of the uterus. Once this membrane is stripped, the hormone prostaglandin is naturally released into the mother's body and initiates contractions.[8] Most of the time doing this only once will not immediately start labor. It may have to be done several times before the stimulant hormone is released, and contractions start.[10] The next method is breaking the mother's water, which is also referred to as an amniotomy. The doctor uses a plastic hook to break the membrane and rupture the amniotic sac. Within a few hours labor usually begins. Giving the hormone prostagladin ripens the cervix, meaning the cervix softens, thins out, or dilates. The drug Cervidil is administered by mouth in tablet form or in gel form as an insert. This is most often done in the hospital overnight. The hormone oxytocin is usually given in the synthetic form of Pitocin. It is administered through an IV throughout the labor process. This hormone stimulates contractions. Pitocin is also used to "restart" labor when it's lagging.

The use of misoprostol is also allowed, but close monitoring of the mother is required.



Postterm pregnancy occurs in 3 to 12% of pregnancies.[11]


  1. Kendig, James W (March 2007). "Postmature Infant". The Merck Manuals Online Medical Library. Retrieved 2008-10-06.
  2. 1 2 Eden, Elizabeth (16 November 2006). "A Guide to Pregnancy Complications". Retrieved 2008-11-13.
  3. "Postmaturity". Morgan Stanley Children's Hospital of NewYork-Presbyterian. Retrieved 2008-11-13.
  4. Kyle, Susan Scott Ricci, Terri (2009). Maternity and pediatric nursing. Philadelphia: Wolters Kluwer Health/Lippincott Williams & Wilkins. p. 652. ISBN 978-0-7817-8055-1.
  5. 1 2 Maher, Bridget (2007-08-10). "Overdue Pregnancy". Vhi Healthcare. Archived from the original on 2008-05-21. Retrieved 2008-11-15.
  6. "Postmaturity". Franciscan Health System. Retrieved 2008-11-09.
  7. Falcao, Ronnie. "Detailed Paper about PostDates".
  8. 1 2 3 Hirsch, Larissa (July 2006). "Inducing Labor". The Nemours Foundation. Retrieved 2008-11-16.
  9. "Labor Induction". American Academy of Family Physicians. January 2008. Retrieved 2008-11-16.
  10. "Stripping Membranes". 2008. Retrieved 2008-11-16.
  11. Buck, Germaine M.; Platt, Robert W. (2011). Reproductive and perinatal epidemiology. Oxford: Oxford University Press. p. 163. ISBN 9780199857746.
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