High-risk pregnancy

A woman is considered to have a high-risk pregnancy when health concerns exist that may threaten the natural course of the development or birth of the baby, or that pose a risk to the mother. In such cases, the mother may need special care, more tests and possibly medication to ensure that she can carry thebaby safely through to delivery.

Conditions linked to high-risk pregnancies include:

  • a very young or very old mother
  • a previous problem pregnancy
  • certain chronic medical problems such as diabetes or high blood pressure
  • a family history of genetic problems
  • Rh incompatibility
  • multiple pregnancy(twins, triplets and so on)
  • women who have had six or more pregnancies
  • women who have had very quick labors in the past
  • prenataltests indicating the baby has a serious health problem

While pregnancy is a natural condition, it can tax even the healthiest woman's body because of changes in blood volume, hormone balance, pressure, the physical burden of pregnancy, and so on. Underlying medical conditions can add even more stress, while complications caused by pregnancy itself (such as preeclampsia or gestational diabetes) can turn a normal pregnancy into a high-risk pregnancy.

While most high-risk pregnancies still end with a healthy mother and child inthe United States, it is still true that in six out of 100,000 births in theUnited States, the mother will die; 16 babies in every 1,000 deliveries alsowill die before, during, or after birth.

A pre-pregnancy visit with a healthcare provider is especially important fora woman who has a medical problem. A woman who has not had a pre-pregnancy visit should contact a healthcare provider as soon as she learns she is pregnant. Often, the provider will schedule the first prenatal visit within a day ortwo, instead of waiting until 8-10 weeks of pregnancy. This is because certain medical conditions can increase the risk of miscarriage. The provider willwant to be sure that any medication is adjusted properly to increase the chance of having a successful pregnancy.

Women coping with a high-risk pregnancy may need the expert advice and care of a perinatologist (an obstetrician specializing in the care of high-risk pregnancies). Perinatologists care for women who have pre-existing medical problems as well as women who develop complications during pregnancy. In addition,a woman with a high-risk pregnancy may be referred to a perinatal care center ("perinatal" has to do with events right before, during, or after delivery)before delivery because special attention will lessen the chance that the baby will become ill or die. A woman is also sent to such a center during laborwhen unexpected problems occur. Usually, these centers work together with obstetricians and a newborn intensive care unit to provide the best care for apregnant woman and her baby.

Before Pregnancy: Risk Factors

Some women have characteristics or conditions that make a pregnancy high-riskeven before they get pregnant. Some conditions, such as thyroid disease, make it difficult to get pregnant and lead to a higher risk of problems in the baby. In addition, when a woman has had a problem in a past pregnancy, she hasa higher risk of having the same problem in future pregnancies.

One of the most common reasons for a pre-pregnancy risk is a woman's age. Girls 15 and under who get pregnant are more likely to develop preeclampsia (a condition characterized by high blood pressure, protein in the urine, and fluid accumulation), and seizures as a result of preeclampsia (these are called eclampsia). Young moms are also more likely to deliver underweight or undernourished babies. On the other hand, women aged 35 and older are more likely todevelop high blood pressure, diabetes, or fibroids (benign growths) in the uterus, or problems during labor. The risk of having a baby with abnormal chromosomes (such as Down syndrome) increases dramatically after age 35.

A woman who weighs less than 100 pounds when not pregnant is more likely to have a baby who is smaller than expected during pregnancy. If she gains less than 15 pounds during pregnancy, her risk of having an undersized baby rises to almost 30 percent. On the other hand, an overweight woman is more likely tohave a very large baby and boosts the risk of developing gestational diabetes and high blood pressure during pregnancy.

Women with a small pelvis (particularly a problem in women less than 5 feet tall) have a higher risk of preterm labor or an abnormally small baby.

Medical Conditions

Many high-risk pregnancies are the result of pre-existing medical conditions.The prospects for successful childbirth in this case depends in large part on the specific medical condition a woman has. Some medical conditions may have a major impact on pregnancy that can endanger her and her unborn baby. Themost serious are:

  • systemic lupus erythematosus (lupus)
  • diabetes
  • chronic high blood pressure
  • kidney disease
  • severeheart disease
  • sickle cell disease
  • thyroid disease
  • blood clotting disorders

Women with kidney disease or lupus (a disease caused by changes in the immunesystem causing inflamed connective tissue and organs) face real risks duringpregnancy, when symptoms can worsen significantly and lead to serious illness. Because these diseases can affect the mother's ability to supply oxygen and nutrients to the baby through the placenta, these diseases can cause problems for the baby as well. Babies of these women may not be able to grow and gain weight properly; some may be stillborn.

Diabetes is a condition that is both affected by pregnancy and affects the course of the pregnancy itself, leading to miscarriages, birth defects, and stillbirths. However, if a woman monitors her blood sugar carefully and uses insulin appropriately, the risk of these problems drops considerably. Unfortunately, pregnancy makes diabetes much harder to control; in general, blood sugarand the need for insulin rise throughout pregnancy.

If high blood pressure is first diagnosed when a woman is pregnant, a doctormay not be sure if the problem was caused by the pregnancy or by another condition. The beneift of treating high blood pressure during pregnancy must be weighed against potential risks to the unborn baby. Late in pregnancy, high blood pressure may indicate a serious threat to the mother and fetus and must be treated promptly.

Sometimes it may be difficult to predict how pregnancy will affect various medical conditions. Of the women who have asthma, for example, 25% will get worse during pregnancy, half will have no change, and 25% will actually get better during pregnancy. No one understands why this is so, and no one can predict the experience any particular woman might have. Thousands of pregnant womencope successfully with a wide range diseases such as asthma, epilepsy, and ulcerative colitis. While these medical conditions usually don't interfere with pregnancy, they are still affected by the mother's condition. Nevertheless,each of these conditions should be monitored very carefully throughout pregnancy.

Because some medical conditions can increase the risk of birth defects, an ultrasound will be done to check the baby early in the second trimester (16-18weeks of pregnancy). At that point, the fetus is large enough so that the doctor can see the organs and structures clearly. Utrasounds may be ordered every few weeks to make sure the medical condition is not interfering with the baby's growth and health.

Structural Defects

Structural defects in a woman's reproductive organs, such as a double uterusor a weak cervix that can't support the developing baby, can increase the risk of a miscarriage. This problem is suspected if a woman has repeated miscarriages; in order to uncover the reason, a doctor may order diagnostic surgery,ultrasound scans, or x-rays before she becomes pregnant again.

Benign growths in the uterus (more common in older women) may increase the risk of preterm labor, problems during labor, abnormal presentation of the fetus, abnormal location of the placenta (placenta previa), and repeated miscarriages.

Too much amniotic fluid in the membranes surrounding the fetus stretches theuterus and puts pressure on the mother's diaphragm, which can lead to pretermlabor or severe breathing problems in the mother. About half the time no oneknows why fluid builds up. The problem can occur if the mother has uncontrolled diabetes, if there is a multiple pregnancy, if mother and baby have incompatible blood types, or if the baby has birth defects. There may be too little amniotic fluid if the baby has birth defects in the urinary tract, is not growing properly, or dies.

Risk Factors During Pregnancy

Not all women who have high-risk pregnancies start out that way. A pregnant woman may be at low risk in the beginning of her pregnancy, but during the ensuing nine months, situations can change that increase her risk. For example,the mother may be exposed to substances that can produce birth defects such as radiation, chemicals, drugs, or infections, or she may develop a medical condition or a complication related to pregnancy.

Drugs that can produce birth defects when taken during pregnancy include alcohol, phenytoin, lithium, streptomycin, tetracycline, thalidomide, and warfarin, and drugs that interfere with of folic acid. Infections that may cause birth defects include chickenpox, German measles (rubella), viral hepatitis, herpes simplex, influenza, listeriosis, mumps, syphilis, toxoplasmosis, and coxsackievirus or cytomegalovirus infections.

Cigarettes are one of the most serious preventable toxins during pregnancy. Although smoking harms both mother and fetus, only about 20 percent of women who smoke quit during pregnancy. It's clear that smoking cigarettes will leadto a baby born at a low weight; the more a woman smokes during pregnancy, theless her baby is likely to weigh. This effect seems to be stronger among older smokers, who are more likely to have short babies who weigh less. Pregnantsmokers also are more likely to have placental complications, premature rupture of the membranes, preterm labor, and uterine infections. A pregnant womanwho doesn't smoke should avoid exposure to secondhand smoke because it may similarly harm the fetus.

Alcohol is another extremely serious but preventable toxin. The risk of miscarriage almost doubles when a woman drinks alcohol in any form during pregnancy, especially if she drinks heavily. Often, the birth weight of babies born to women who drink during pregnancy is below normal. The average birth weightis about 4 pounds for babies exposed to alcohol, compared with 7 pounds for all babies.

Infections can also be a problem. If a pregnant woman has had a bladder infection in the past, her doctor will evaluate a urine sample early in the pregnancy. If bacteria are detected, antibiotics may prevent a kidney infection, which is associated with preterm labor and premature rupture of the membranes.Bacterial infections of the vagina during pregnancy also may lead to pretermlabor or premature rupture of the membranes. Treating the infection with antibiotics reduces the likelihood of these problems. But any illness that causesa high fever (over 103 F.) in the first 3 months of pregnancy can cause problems, increasing the chance of miscarriage and nervous system defects in thebaby; fever in late pregnancy boosts the risk of preterm labor.

A woman who has had three miscarriages in a row during the first 3 months ofpregnancy has about a 35 percent chance of having another miscarriage, and therefore is at high risk with each subsequent pregnancy. Women who have had astillborn baby between the fourth and eighth months of pregnancy or preterm labor in a previous pregnancy are also more likely to have a miscarriage. Somedoctors recommend that before trying to become pregnant again, a woman who has had a miscarriage should be checked for chromosomal or hormonal abnormalities, uterine or cervical defects, connective tissue disorders (such as lupus), or an immune problem such as an Rh incompatibility.

Preterm (early) labor

premature labor is one of the big concerns in high-risk women. In fact, the most common reason for referral to a perinatal specialist or center is the risk of premature labor (before 37 weeks), which often occurs when the fluid-filled membranes containing the baby break too early. Treatment at a perinatal care center may lessen the chance that the baby will be born prematurely.

Labor often begins early if the fetus is in an abnormal position (such as breech), when the placenta detaches from the uterus too soon, if the mother hashigh blood pressure, or when too much amniotic fluid surrounds the fetus. Other causes of preturm labor include: previous uterine surgery, bleeding, stress, structural defects in the uterus or cervix, a multiple pregnancy, pneumonia, kidney infection, and appendicitis. About 30 percent of women who have preterm labor have infections of the uterus; it's not known if antibiotics willhelp prevent labor from progressing.

The more preterm deliveries a woman has had, the greater chance she has of more preterm deliveries in the future. Likewise, a woman whose first baby was born too small (growth-retarded) may have the same problem in the next pregnancies.

While preterm labor is a high risk, so is delayed labor. Pregnancies that last beyond 42 weeks end in death of the baby three times more often than in a normal term pregnancy. Electronic heart monitoring and ultrasound scanning areused to monitor the fetus to prevent this situation.

Most chronic medical conditions don't lead to complications in pregnancy, however. With frequent visits to healthcare providers and careful attention to medication, women with medical problems usually enjoy healthy, successful pregnancies.

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