Chapter 30 Medical explanation

Here is a report that I came across on the internet.

Amniotic Fluid Abnormaliti
The amniotic fluid that surrounds a developing baby plays a crucial role in normal development. This clear-colored liquid cushions and protects the baby and provides it with fluids. By the second trimester, the baby is able to breathe the fluid into his lungs and to swallow it, promoting normal growth and development of the lungs and gastrointestinal system. Amniotic fluid also allows the baby to move around, which aids in normal development of muscle and bone.

The amniotic sac that contains the embryo forms about 12 days after conception. Amniotic fluid immediately begins to fill the sac. In the early weeks of pregnancy, amniotic fluid consists mainly of water supplied by the mother. After about 12 weeks, fetal urine makes up most of the fluid.

The amount of amniotic fluid increases until about 28 to 32 weeks of pregnancy, when it measures a little less than 1 quart. After that time, the level of fluid generally stays about the same until the baby is full term (about 37 to 40 weeks), when the level begins to decline.

In some pregnancies, however, there may be too little or too much amniotic fluid. These conditions are referred to as oligohydramnios and polyhydramnios, respectively. Both can sometimes cause problems for mother and baby or be a sign of other problems. However, in the majority of cases, the baby is born healthy. Here’s what expectant parents should know about these disorders.

How are oligohydramnios and polyhydramnios diagnosed?
An ultrasound examination can diagnose either too little or too much amniotic fluid. Doctors commonly measure the depth of the fluid in four quadrants in the uterus and add them up. This method of measuring amniotic fluid is referred to as the amniotic fluid index (AFI). If the amniotic fluid depth measures less than 5 centimeters, the pregnant woman has oligohydramnios. If fluid levels add up to more than 25 centimeters, she has polyhydramnios.

How common is oligohydramnios?
About 8 percent of pregnant women have too little amniotic fluid. Oligohydramnios can develop at any time during pregnancy, though it is most common in the last trimester. About 12 percent of women whose pregnancies last about two weeks beyond their due dates (about 42 weeks gestation) develop oligohydramnios, because the level of amniotic fluid decreases by about half by 42 weeks gestation.

What fetal problems and pregnancy complications are associated with oligohydramnios?
The problems associated with too little amniotic fluid differ depending on the stage of pregnancy. Oligohydramnios that occurs in the first half of pregnancy is more likely to have serious consequences than if it occurs in the last trimester. Too little amniotic fluid early in pregnancy can compress fetal organs and cause birth defects, such as lung and limb defects. Oligohydramnios that develops in the first half of pregnancy also increases the risk of miscarriage, preterm birth and stillbirth.

When oligohydramnios occurs in the second half of pregnancy, it may be associated with poor fetal growth. Near term, oligohydramnios may increase the risk of complications of labor and delivery, including potentially dangerous umbilical cord accidents that can deprive the baby of oxygen, and stillbirth. Women with oligohydramnios are more likely than unaffected women to need a cesarean delivery.

What causes too little amniotic fluid?
The causes of oligohydramnios are not completely understood. The majority of pregnant women who develop oligohydramnios have no identifiable cause.

The most important known causes of early oligohydramnios are certain birth defects and ruptured membranes (bag of waters that surrounds the baby). About 7 percent of babies of women with oligohydramnios have birth defects. Birth defects involving the kidneys and urinary tract are the most likely causes because affected fetuses produce less urine (which makes up most of the amniotic fluid).

Certain maternal health problems also have been associated with oligohydramnios. These include high blood pressure, diabetes, systemic lupus erythematosus (SLE) (an autoimmune condition) and placental problems. A group of medications used to treat high blood pressure, called angiotensin-converting enzyme inhibitors (like captopril), can damage the fetal kidneys and cause severe oligohydramnios and fetal death. Women who have chronic high blood pressure should consult their health care provider prior to pregnancy to make sure their blood pressure is under control and that any medications they take are safe during pregnancy.

How is oligohydramnios treated?
Recent studies suggest that women with otherwise normal pregnancies who develop oligohydramnios near term probably need no treatment, and their babies are likely to be born healthy. They do, however, require close surveillance. Their health care provider will probably recommend weekly or more frequent ultrasound examinations to see if the level of amniotic fluid is decreasing. If the level of amniotic fluid does drop, he or she may recommend inducing labor early to help prevent complications during labor and delivery. About 40 to 50 percent of cases of oligohydramnios resolve themselves without treatment in as little as a few days.

Besides ultrasound examinations, providers will likely recommend tests of fetal well-being, such as the nonstress and contraction stress tests, both of which measure fetal heart rate. These tests can alert the provider that the baby is having difficulties. In such cases, the provider is likely to recommend early delivery to help prevent serious problems.

Developing babies with poor growth whose mothers have oligohydramnios are at high risk of complications, such as asphyxia (lack of oxygen), both before and during birth. Mothers of these babies are monitored very closely, and they sometimes need to be hospitalized.

If a woman has severe oligohydramnios near the time of delivery, her provider may suggest inserting salty water (saline solution) through the cervix into the uterus. This may help reduce complications during labor and delivery and reduce the need for cesarean delivery.

Studies suggest that this approach is especially beneficial when fetal heart rate monitoring shows that the baby may be having difficulties. Some studies also suggest that women with oligohydramnios can help increase their levels of amniotic fluid by drinking extra water. Also, many doctors suggest decreasing physical activity or even bedrest. A pregnant woman with oligohydramnios should discuss with her health care provider which, if any, treatment may be best for her.