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. 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.
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. Some postmature babies will show no or little sign of postmaturity.
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. 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. 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.
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. A rate of fewer 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 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.
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.
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