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High-Risk Pregnancy
Pregnancy is a normal physiological process usually resulting in a healthy mother and infant. Identification of a number of risk factors that may cause a poor pregnancy outcome causes the pregnancy to be considered a high-risk pregnancy. Identification of these risk factors, either before or during pregnancy, allows for appropriate intervention to reduce the possibility of a poor outcome.
Conditions that may place a pregnancy at high
risk include:
Maternal Conditions
1. Medical complications including cardiac disease,
renal disease, hypertension or diabetes.
2. Alcohol, substance or drug abuse.
3. Infections including HIV, chlamydia, genital
herpes, chickenpox, rubella.
Fetal Conditions
1. Family history of genetic disorders.
2. Previous history of preterm labor.
All patients should have continuous risk assessment performed at every prenatal visit during pregnancy to identify these factors which may require increased surveillance and/or intervention. Significant factors in medical or family histories that require evaluation include ethnic background with an increased risk of Sickle Cell Anemia in blacks, Alpha thalassemia in Asian peoples, Beta-thalassemia in Mediterranean North African, Indian and South east Asian peoples, and Tay Sachs disease in people of Jewish descent.
If a specific risk factor is identified, then appropriate testing is initiated to identify the potential to cause a poor pregnancy outcome.
At the present time, amniocentesis is offered to all women of advanced maternal age (35 years or older). If blood is taken from mothers however differences in concentrations of multiple biochemical markers have been observed in the serum of mothers with Down syndrome babies compared to normal fetuses. These markers have been combined into a triple/quadruple screen (MS-alpha feto protein (AFP), human chorionic gonadotropin (hCG), estriol and inhibin). The risk of Down syndrome is increased with a pattern of low MS-AFP, decreased serum estriol and elevated serum HCG between 15 and 20 weeks of gestation. Use of this non-invasive test has allowed women to appropriately evaluate a more specific risk for Down syndrome and avoid amniocentesis that carries a 1/200 risk of fetal loss.
Healthcare providers, as part of regular prenatal care, provide evaluation and laboratory screening to ensure ongoing maternal and fetal well being. Risk factors that are considered include:
Blood type: Rh factor is obtained to identify patients with a potential for incompatibility between the mother and fetal blood because of the presence of antibodies in the blood. Mothers are screened for antibodies at their first visit and at their 28th week of gestation. The major antibody is Rhesus factor D, and if the screen is negative for antigen D, Rh immune globulin is given to prevent fetal red blood cells which enter the maternal circulation from causing damage.
Prenatal screening for HIV is recommended to identify newly infected patients because the use of anti-retroviral therapy decreases the risk of transmission to the fetus from 25% to 8%.
New diabetes, called Gestational Diabetes, can develop in pregnancy in about 3% of women. The condition causes the development of macrosomia (large babies) with an associated increased risk of cesarean delivery and birth trauma. Screening is routinely performed on all patients at 24-28 weeks by use of a 50gm oral glucose level. Patients who test positive are encouraged to modify their diet and exercise or may require insulin to maintain appropriate maternal serum glucose levels to grow a normal sized baby.
At all of their healthcare visits, patients should
be aware of any risk factors present that may affect their outcome. Patients
should ask about the tests required to identify the pregnancy-related problems
and the accuracy of such tests. The healthcare provider and the patient
should weigh the pros and cons of any suggested treatment and the evidence
for its usage.