Post-term pregnancy is defined as pregnancy that goes beyond 42 weeks since the woman’s last menstrual period. The reported frequency varies from 4-14% depending on the different factors of the population surveyed.
The main concern of post-date pregnancy is that the placenta may not work as efficiently as it ages beyond 41 weeks gestation. This can lead to a number of effects, including dry skin, loss of fat and meconium (fetal wastes) in the bag of waters. In rare cases, it can result in low oxygenation, meconium aspiration syndrome, convulsions or even death. However, the vast majority of babies are born healthy whether they arrive at 40 weeks or later.
Concern for the baby’s welfare has prompted considerable controversy surrounding the management of the time intervals prior to and beyond the point of postdate pregnancy. There are two main methods of care after 41 weeks:
- Expectant Management
- This is a wait-and-see approach, along with various tests to monitor fetal well-being. An NST (non-stress test) involves listening to the baby’s heart rate for a period of time to monitor for a normal pattern. Often at 42 weeks an ultrasound will be recommended. This test can assess the baby’s health by observing fetal movement, and assessing levels of amniotic fluid.
- Labour Induction
This involves going to the hospital to have your labour artificially induced by medications. Two frequently use techniques are:
- i) Prostaglandins — A doctor applies medication (usually a gel) to your cervix;
- ii) Oxytocin — A synthetic hormone is given intravenously to stimulate labour contractions.
More about Induction
The rate of induction beyond 41 weeks gestation has been steadily increasing so that in 1999 it was recorded to be as high as 38%. According to the American College of Obstetrician and Gynecologists (ACOG), the increased rates are related to the widespread availability of cervical ripening agents, pressure from patients and physicians, as well as legal constraints.
Prior to an induction, a woman’s cervix is evaluated for ripeness. If the cervix is firm and closed, Prostaglandins is often applied to soften the cervix. Frequently, more then one application is required before labour can begin. The baby’s heart rate will be monitored prior to an induction and afterwards for approximately 30 minutes. Once a cervix is considered ripe enough the doctor will either continue with the prostaglandins or use a synthetic hormone called Oxytocin. This hormone is similar to the body’s own natural hormone and generally is effective to begin labour. Oxytocin is always given intravenously, and will require continuous monitoring of both the mother and baby to ensure the procedure is being tolerated well.
Advantageous of Induction
- Inductions are typically arranged for a scheduled time at the hospital, which may help families to organize for their baby’s arrival,
- For women whose care provider shares a call schedule, it may ensure your preferred provider is present.
- Inductions can also eliminate the need for the ongoing waiting of labour to begin.
Disadvantageous of Induction
- An intravenous and monitoring instruments can limit a mother’s ability to move into different positions and locations during labour which may lead to longer intervals in bed.
- Adverse complications caused by induction have also been well-documented and include contractions that are difficult to handle, increased need for epidurals, hyper-stimulation of the uterus, possible placental abruption and uterine rupture.
- Additional risks factors for the baby may include heart rate abnormalities, hypoxia, and fetal distress.
- There has been little research on women’s actual experience and satisfaction with induction, so it is difficult to say how women rate this experience.
More on Expectant Management
At 41 weeks a woman’s chances of giving birth naturally are still very much in her favor. Six women out of ten will have their babies in the next 3 days, and nine will have it in the next 7 days. Health care providers will often recommend monitoring the baby to ensure it is managing well. A Non-stress Test (NST) is often done between 41-42 weeks and involves tracking the baby’s heart rate with a monitor for a minimum of 20 minutes. The pattern of the baby’s heart rate is indicative of its general health. Ultrasound is often recommended to assess fetal health by monitoring fetal activity, and determining levels of amniotic fluid. These tests indicate how the baby is managing in real time but cannot predict the baby’s future welfare. Daily monitoring of fetal movement is also recommended.
Knowing which pregnancies are truly at risk would be the ideal situation in the case of post-term pregnancy. Unfortunately we have not developed or adequately researched methods to determine this. Research has determined that:
- Smaller term babies run a greater risk then larger babies for complications,
- Sometimes there is a familial or genetic component to post-term pregnancy. A small correlation between mothers, daughter, and sisters has been seen in this regard.
- The strongest indicator for a prolonged pregnancy, and reduced rate of post-date complications occurs with women who have had a previous prolonged pregnancy.
- Post-term babies have a greater tendency to be boy babies.
- Daily monitoring of the time it takes your baby to move 10 times should be fairly consistent.
- If you’re paying close attention, and you are not aware of fetal movement you should contact your care provider.
- Fetal movement counts are a positive way to connect with your baby.
Preventing Post-term Pregnancy
Women can try to stimulate their labour through alternate methods, but for the most part these methods have not been researched for safety and/or effectiveness. Things you may consider are:
- Walking — which naturally pushes your baby’s head against the cervix.
- Sexual intercourse — as both nipple stimulation and the release of hormones with orgasm and ejaculation are helpful to soften the cervix in preparation for labour.
- Women who use upright and forward leaning posture, particularly during the last 6 weeks of pregnancy (2-3 weeks for a multigravida) give the baby an excellent chance of positioning itself into the best position for labour. Activities of swimming and yoga encourage this, while semi-reclining, sitting crossed legs, and squatting are not advisable.
Professional guidance may be sought for other modalities including hypnosis, acupuncture and homeopathy.