”Only about 5 % of all babies arrive on the actual date that they are expected. The expected date of delivery EDD is only a statistical average, and studies have shown that as many as 40 % of babies are born more than a week after the EDD. This 40 percent of babies are born that are ”Overdue” breaks down as follows, 25 % of babies are born in the 42nd week of pregnancy, 12 % in the 43rd week and 3 % of babies are born in the 44th week of pregnancy.”
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One of the main difficulties in deciding whether a baby is actually overdue or not is that the precise date of conception in any particular pregnancy is extremely difficult to pinpoint. Even if you have a regular menstrual cycle of 28 days (the standard on which EDD chart is based) , the date of ovulation is only known approximately.
Apart from this uncertainty about the exact date of ovulation, every baby is different and therefore it is unrealistic to expect all babies to mature in precisely the same number of days. Moreover, since labor is initiated by your baby producing certain hormones as he reaches full maturity, it follows that the actual date of delivery can vary fairly widely, even in ”textbook” pregnancies.
However, doctors do become concerned if a pregnancy continues much beyond the estimated date of delivery. This is because post-maturity and possible placental insufficiency pose some risks to the health of your unborn baby. The longer the baby continues to grow inside the uterus, the larger he is likely to become, which, in turn, will increase the chances of a difficult labor, and the possibility that the placenta will not be able to continue to support the baby over an extended period.
Doctors also take into consideration whether you have a persnol or maternal family history of longer than average gestations (43 or 44 weeks for example). If this is the case, your doctor will probably be more willing to allow you to go for more than two weeks overdue without inducing the labor, although you will be closely monitored in case any problems do develop and, in practice, most women are quite desperate to deliver by this stage of pregnancy.
Labour may be delayed if your baby’s head is too big to pass through your pelvis. This disproportion may prevent the baby’s head from becoming engaged.If this is the case a Caesarean section may be required.
An overdue baby is in danger of being post-mature. If a baby is post-mature this means that he will have lost fat from all over his body, particularly from his tummy. Consequently, his skin will look red and wrinkled as if it doesn’t fit him, and it may have begun to peel. Very few babies are actually post-mature, however, because post-maturity depends not only on the baby’s condition, but also on his placenta, it is difficult to predict which babies will be at risk.
These include a longer and more difficult labour, because the post-mature baby tends to be bigger than usual and the bones in his skull tend to be harder (which means that his descent through the birth canal is likely to be more traumatic for both him and for yourself) and there is also an increased risk of stillbirth (the risk of stillbirth doubles by the 43rd week and triples by the 44th week). A further risk is that a uterus that is slow to begin to start labour may also be relatively inefficient during the labour itself.
At term, the placenta the organ that links the blood supplies of the mother and baby, looks rather like a piece of raw liver, is about the size of a dinner plate, and measures about 2.5cm (l in) in thickness. The maternal side is divided into wedge shaped chunks called cotyledons.
The placenta has substantial functional reserves, readily adjusts to injury, repairs damages due to ischaemia (lack of oxygen) and does not undergo ageing. The widely held view that ageing occurs progressively during the course of a normal pregnancy is due to a misinterpretation of the appearance of different placental components over the duration of the pregnancy.
Unquestionably, however, there are changes in the character of the villi around the placenta as pregnancy advances, and by the 36th week of pregnancy there may be a deposition of calcium within the walls of the small blood vessels, and a protein deposit may appear on the surface of many of the villi. Both of these changes have the effect of limiting the flow of nutrients and waste across the placenta, but this is balanced by the proximity between fetal blood vessels and the villi, both factors enhancing the exchange of nutrients.
If labour does not start at the right time (this varies from pregnancy to pregnancy, but is usually considered to be two weeks either side of the EDD), the placenta may then start to become relatively inefficient. However, this does happen slowly and at 42 weeks the placenta should still be capable of supplying your baby with sufficient nutrients. Problems occur when, occasionally the placenta fails to nourish and support your baby adequately. This is known as placental insufficiency and would be a reason for inducing labour.
”When engagement is late in a first pregnancy, doctors worry in case disproportion is preventing your baby’s head from engaging, as this could obstruct labour“.
In order to check whether your baby’s head will actually engage in, and pass through, your pelvis, your doctor will perform a simple test as follow.
You will be asked to lie on your back. When you are in this position, your doctor will be able to feel your baby’s head resting just at the pelvic brim.
When you are propped up on your elbows, however your baby’s head slips easily into your pelvis, so showing there is no problem with pelvic disproportion.
”Babies past their EDDs are monitored closely, and there are a number of different ways of keeping a check on your baby“.
The most accurate sign that all is well with your baby is if you can detect regular fetal movements. Since mothers, and babies, are different, the amount of movement that is normal for each individual pregnancy varies. You are the best judge of whether your unborn baby is acting normally, and you can monitor his activity using a kick chart.
This may be used to check the baby’s heartbeat by providing a continuous sound or paper recording. If the heartbeat is satisfactory, it is usually judged unnecessary to perform other tests, or to induce labour.
You will probably be given an ultrasound scan to assess the volume of amniotic fluid. If this is becoming dangerously low, then you will be advised to have your pregnancy induced.