Postterm pregnancy | |
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Classification and external resources | |
ICD-10 | O48, P08.2 |
ICD-9 | 766.22 |
DiseasesDB | 10417 |
eMedicine | med/3248 |
MeSH | D007233 |
Postmaturity is when a baby has not yet been born after 42 weeks of gestation, two weeks beyond the normal 40.[1] Post-term, postmaturity, prolonged pregnancy, and post-dates pregnancy all refer to postmature birth. Post-mature births do not have any harmful effects on the mother, but the fetus, however, can begin to suffer from 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 fecal matter, which is not typical until after birth, and the child breathes it in, then the baby could become sick with pneumonia. Postterm pregnancy may be a reason to induce labor.[2]
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The causes of post-term births is 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[3]. Post-mature births can also be attributed to irregular menstrual cycles. When the menstrual period is irregular it is very difficult to judge how and when the ovaries would be available for fertilization and subsequently result in 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.[4] However in most first world countries where gestation is measured by ultrasound scan technology, this is less likely.
Different babies will show different symptoms of postmaturity. The most commons symptoms 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.[5] Some postmature babies will show no or little sign of postmaturity.
Once a pregnancy has surpassed the 40 week gestation period, doctors closely monitor the mother for signs of placental deterioration. Towards the end of pregnancy calcium is deposited on the walls of blood vessels and proteins are deposited on the surface of the placenta, which changes the placenta. This limits the blood flow through the placenta and ultimately leads to placental insufficiency and the baby is no longer properly nourished. Induced labor is strongly encouraged if this happens.
Post-term babies may be larger than an average baby, thus increasing the length of labor. The labor is increased because the baby's head is too big to pass through the mother's pelvis. This is called cephalopelvic disproportion. Caesarean sections are encouraged if this happens.
When post-mature babies are larger than average forceps or vacuum delivery may be used to resolve the difficulties at the delivery time. Difficulty in delivering the shoulders, shoulder dystocia, becomes an increased risk.[6]
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. 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 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 doctors guess at the age can be quite off. The actual placenta won't start to deteriorate until about 48 weeks. The reason why doctors favour induction by 42 weeks is because of the risks that are present.
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 is a type of ultrasound that measures the amount of blood flowing in and out of the placenta.[7]
A woman who has reached 42 weeks of pregnancy is likely to be offered induction of labour. Alternatively, she can chose expectant management, that is, she waits for the onset of labour naturally. Women opting for expectant management, may also choose to carry on with additional monitoring of their baby, with regular CTG, ultrasound and biophysical profile. There is anecdotal evidence online of "10 month mamas" and women choosing to wait to 43 weeks and 44 weeks of pregnancy.[8] Risks of expectant management vary between studies.[9]
Inducing labor is artificially starting the labor process by using medication and other techniques. Labor is usually only induced if there is potential harm on the mother or child.[10] 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.[11] Labor induction is not always the best choice because it has its own negative 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's completely necessary.[12]
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 starts the contractions.[13] 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.[14] 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 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.
Inducing labor does not instantly start the birthing process. Sometimes days may go by before labor initiates. If this happens, then a Cesarean section will probably be performed. If labor has not started a long time after the membranes have been ruptured, the risk of infection increases dramatically. Therefore, if rupturing the amniotic sac does not induce labor, the doctor will try a new method. The use of prostaglandin and pitocin can cause abnormal contractions. In this case, the doctor will lower the dosage of pitocin or prostaglandin. The risk of tearing the uterus increases when these medications are used. Pitocin can also cause low blood sugar or low blood sodium levels, which can cause seizures. When a mother is not sure of her last menstrual period it can cause problems once the expected date approaches. If labor is induced on a mother who miscalculated her last period, the baby could actually be born too early. Women that have first trimester bleeding or irregular periods are most affected by this. When a baby is thought to be post-term but is actually born too early, it is called late pre-term. Late pre-term babies may have jaundice, trouble with feeding or breathing, or difficulty maintaining a normal body temperature.
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