The cervix and miscarriage

Incompetent cervix

Losing a baby in the second trimester can be a devastating experience, as we read in Paul’s story. One of the especially sad facts about cervical incompetent is that these women have been losing pregnancies regularly, often at the same week in each pregnancy. Not only is any miscarriage a harrowing experience, but to find yourself repeatedly losing healthy, normal, babies—who, if you could see or hold, look like miniature newborns—then the experience can obviously lead a woman, and her husband, to despair. Later in this chapter we will hare the story of Laura, who has indeed gone through just this type of experience. This is unfortunately a very common problem. But, with new techniques we can now offer much more hope for successful treatment.

The actual incidence of incompetent cervix is unknown but is thought to be about 1 to 2 percent of normal deliveries. It has been estimated that an incompetent cervix is the cause of up to one-fifth of late miscarriages (that is, those following the 12th week).

Technically speaking, a cervix is classified as incompetent if it fails to maintain an intrauterine pregnancy to term. The cervix begins to dilate far too early and easily, the amniotic membranes push through, and, following either a dramatic rupture of the membranes or blood loss, you go into a rapid, short premature labor. The baby is then born too early for independent life. Only recently have doctors understood just what can happen to the cervix. Although the procedure of inserting a stitch to hold the cervix closed has been in practice since 1951, we are now more competent in diagnosing and treating the condition successfully.
Normally, the cervix acts as the plug that holds the pregnancy in place. The cervix is mainly composed of collagen, or connective tissue, and only 10 percent of ut is muscle. When you are not pregnant the cervix is rigid, fibrous as “riprning,” and that is probably caused by the action of the pregnancy hormones. If the cervix ripens too early, the pregnancy can be pushed through a weakened cervix from about the 14th to the 20th week.

All too often the cervix has been affected prior to the pregnancy by trauma, for example, from previous D&C’s or elective terminations of pregnancy. Until recently no one realized how gingerly the cervix should be treated. For example, one method of treatment for painful periods used to be dilating, or overstretching, the cervix, the cervix, which usually tore the muscle fibers and led to incompetence. This treatment is now unnecessary because of the availability of effective medications. With our increased medical knowledge, there is no reason why induced abortions (terminations) should now result in incompetent cervix.

If an abortion is needed after the 10th or 11th week, when the cervix would otherwise have to be opened, or dilated, unduly, your doctor dose not have to use metal dilators that can tear and damage, using laminaria (seaweed) sticks, which are inserted into the cervix and left overnight before the procedure. The risks of mechanical trauma and damage to the cervix can thus be obviated.

The cervix can unfortunately also be damaged in childbirth, torn either by the passage of the infant during delivery or by instruments such as forceps or a vacuum extractor. The other major cause of an incompetent cervix, as we discussed in the previous section of the top of the uterus as the pregnancy grows, force the cervix to open below.

A diagnosis of competent cervix can be made from a combination of your personal medical history, which is most important, and an internal examination. Shortly after your last period ends and you know you’re not pregnant, if you doctor can pass a size 6 Hegar dilator through the cervix into the uterine canal, then he would strongly suspect such a diagnosis.

Hysterography, described in the previous section, can also be used for diagnosis. The dye may spill back around the instrument that hs been placed in the cervix and through which the dye is injected, o show the width of the cervix. Ultrasound, in expert hands, can also be used dor diagnosis of incompetent cervix, especially if you are already pregnant. On the screen, you may be able to see a widely dilated cervix, with membranes and amniotic fluid bulging down. With use of the newly introduced transvaginal ultrasound, more is being learned about diagnosing abnormalities of the cervix.

The main indiction of a weak cervix, however, remains a past history of recurrent miscarriages between 14 and 24 weeks. Usually there will have been little heavy bleeding; the membranes may even have ruptured before any contractions were felt. The contractions that do come are short and usually quite painless. The fetus is often, very sadly, born alive.

Prevention of damage to the cervix
Doctors treat D&C procedures with caution. They are aware that any woman in her productive years should not have her cervix forcibly ripen the cervix the night before, using the seaweed (laminaria) I described earlier, or by placing prostaglandins in the vagina, which also ripen the cervix overnight. They then do not have to do much dilation (the D part of the D&C) because you will already have been dilated.

If you receive word of an abnormal pap smear that may eventually need to be treated, cryosurgery (freezing) or laser therapy may be used, rather than a surgical cone biopsy, where some of the cervix is cut away, which may lead to incompetence. So your doctor now has the alternative of these newer methods that can be used with less trauma to the cervix and which are just effective.

At medical schools, young doctors in training are being taught such methods of prevention of illness, at the same time as they are discussing methods of treatment. This new attitude runs through all areas of medicine.

Why dose an incompetent cervix give way from 12 to 14 weeks on?

In the previous section, I mentioned that the cervix is made up of only about 10 percent muscle; the rest of it is a fibrous material that can stretch and soften in pregnancy. The cervix opens at ovulation allowing the entrance of sperm, but apart from that time it is normally closed.

During pregnancy, the cervix softens slightly, but otherwise it remains tight and is filled with a very thick or viscid mucus plug that stays in place until very late in pregnancy. At that point the cervix starts to shorten, or efface, because it is beginning to open so the baby’s head can go through it. The cervix must remain tightly closed to protect the fetus and uterine contents from the introduction of infection from the outside or the vagina.

The part of the uterus above the cervix is made up mainly of strong muscle. During early pregnancy, the uterus increases in size due to pregnancy hormones, which cause muscle fibers in the body of the uterus to increase in number and to lengthen. Then, from the middle of the second trimester, about the 12th to 14 week on, the uterus also gets bigger because the growing fetus and amniotic sac now push up and cause its expansion. This is what normally happens before delivery. The uterus gets large, and at around 40 weeks, the strong muscle helps expel the baby through the cervix opening.

However, if the cervix is weak, or incompetent, or if the uterus is misshapen, this normal sequence of events does not occur. When there is an abnormality, the muscle in the uterus is often replaced by fibrous tissue that cannot expand. As the baby grows and pushes up on the top of the uterus (fundus), the uterus refuses to give because of the fibrous tissue, and the pregnancy begins to act like a metal rod—pushing down on the cervix, which will start dilating. This will precipitate a rupture of the membranes, and a rapid miscarriage follows.

Symptoms are very few. But, if you do notice that your uterus is contracting and becoming very hard at this time, if there is a very heavy mucus discharge or any vaginal bleeding, you should report to your doctor. Often no pain is experienced until the miscarriage is already well advanced. However, pressure on the cervix may produce a pain in the vagina that has been described as “like a knife pushing upward from the vagina into the pelvis.” Severe backache may also occur. Any such symptoms around this time of pregnancy should be immediately reported.

However, if a diagnosis has been made and a stitch can be put in at the correct time, the success rate for producing a healthy term baby is very good, at least 80 to 90percent. New studies have shown that the earlier in pregnancy the stitch is put in, and the higher upon the cervix your doctor can place it, the more effective is its hold. You and your doctor will be doing your best to stimulate nature. The cervix needs to be closed and tight to maintain a pregnancy.

Sometimes an incompetent cervix, especially one that happened beyond about 20 weeks, may be associated with uterine contractions. It is not known whether this is true premature labor, or whether the weak cervix is causing the contractions. Nevertheless, at this late stage in addition to the stitch, your doctor may put you on the drug ritodrine to prevent further contractions. The drug is safe to take in pregnancy;  its only side effect on you is a rapid heart beat. It has been approved by the Food and Drug Administration (FDA) for use in the united states for the past four to five years, even though it has been used in Europe and other parts of the world for at least twice that length of time. It only has FDA approval for use in pregnancy once the 20-week stage of pregnancy has been attained.