Are You Overdue?
.Only about five percent of all babies arrive on the actual date that they’re expected. The expected date of delivery is only a statistical average, and studies have shown that as many as 40 percent of babies are born more than a week after their EDD. This 40 percent of babies that are “overdue” arrive as follows: 25 percent of babies are born in the forty-second week of pregnancy, 12 percent in the forty-third week, and three percent of babies are born in the forty-fourth week of pregnancy.
BEING OVERDUE
The exact date of conception in any particular pregnancy is extremely difficult to pinpoint, and this makes it hard to decide whether a baby is overdue. Even if you have a regular menstrual cycle of 28 days (the standard on which the EDD chart is based), the date of ovulation is only known approximately.
As well as this uncertainty about the exact date of ovulation, every baby is different, so it’s unrealistic to expect them all to mature in precisely the same number of days. Since labor is initiated by your baby’s producing certain hormones as he reaches full maturity, it makes sense that the actual date of delivery can vary fairly widely-even in “textbook” pregnancies.
Doctors do become worried, though, if a pregnancy continues much beyond the estimated date of delivery. This is because post-maturity and possible problems with the placenta (placental insufficiency) pose some risks to the health of your unborn baby (see Post-maturity, Risks, opposite). The longer your baby goes on growing inside your womb, the larger he is likely to become, which, in turn, will increase the chances of a difficult labor. There’s also the risk that the placenta will not be able to continue to support your baby over an extended period.
Doctors will also ask about your family history-have you or your mother had longer-than-average pregnancies (lasting 43 or 44 weeks, for example)? If so, your doctor will probably be more willing to let you to go more than two weeks overdue without suggesting that you’re induced-although you’ll be closely monitored in case any problems do develop. (In practice, most women are desperate to have their babies by this stage of pregnancy.) After 40-41 weeks, you will have antepartum testing, either ultrasound or non-stress testing, to determine if you need to be induced, or if you can safely continue your pregnancy.
Pelvic disproportion Your labor may be delayed if your baby’s head is too big to pass through your pelvis. This disproportion may prevent your baby’s head from becoming engaged.
POSTMATURITY
An overdue baby is in danger of being post-mature. A post-mature baby will have lost fat from all over his body, particularly from his tummy. 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 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.
Risks A post-mature baby tends to be bigger than average, which can make your labor longer and more difficult. Also, the bones in his skull tend to be harder, which means that his descent through the birth canal is likely to be more traumatic, both for him and for you, and there’s also an increased risk of stillbirth-the risk of stillbirth doubles by the forty-third week of pregnancy and triples by the forty-fourth week. Another risk is that a uterus that’s slow to start labor may also be relatively inefficient during the labor itself.
YOUR BABY’S PLACENTA
At term, the placenta-the organ that links the blood supplies of the mother and baby-looks like a large piece of raw liver. It is about the size of a dinner plate, and measures about 1 inch (2.5 centimeters) thick. The maternal side is divided into wedge shaped chunks called cotyledons.
The placenta has substantial reserves, readily adjusts to injury, repairs damages due to ischemia (lack of oxygen), and does not undergo aging. The widely-held view that the placenta ages progressively during your pregnancy is due to a misinterpretation of the appearance of different parts of the placenta over the duration of the pregnancy.
Unquestionably, though, there are changes in the character of the villi (small projections) around the placenta during the pregnancy, and by the thirty-sixth week there may be deposits 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 can limit the flow of nutrients and waste across the placenta, but this is balanced by the fact that the fetal blood vessels and villi are close together, which makes the exchange of nutrients easier.
Risks If labor does not start at the right time (this varies from pregnancy to pregnancy, but is usually considered to be two weeks on either side of the EDD), the placenta may then start to become relatively inefficient. This happens slowly, and at 42 week the placenta should still be capable of supplying your baby with enough nutrients for his needs.
There can be problems when, occasionally, the placenta fails to nourish and support your baby adequately. This is known as placental insufficiency, and in these circumstances you’ll be advised to have your labor induced.
