Submitted by Armen Hareyan on Dec 29th, 2004
Should a woman who delays childbirth into her late 30s or 40s be concerned? While most women enjoy healthy pregnancies and healthy babies, childbearing after age 35 does carry greater medical risks, says Brian Clark, Ph.D., M.D., head of The Cleveland Clinic's Section of Reproductive Genetics in the Department of Obstetrics and Gynecology.
Couples now have the option to take part in sophisticated genetic screening and diagnostic tests designed to detect abnormalities such as Down syndrome, cystic fibrosis, sickle cell disease or spina bifida early in a pregnancy. Below, Dr. Clark offers insight into such prenatal testing and diagnosis.
Q: What's the benchmark age for prenatal screening?
A: First, it is important to understand the difference between screening and a diagnostic test. Screening calculates the risk of having a child with a certain disease or condition and generally is quick and easy to do. A diagnostic test detects a certain disease or condition. A positive result usually means that the child does have the disease or condition. These tests are generally more invasive and more expensive.
When a women is in her mid-30s or older, she is at greater risk for miscarriage, having a child with chromosomal abnormalities, or developing medical complications during pregnancy, such as gestational diabetes. Because of these risk factors, women in this age group should be offered screening and/or diagnostic tests.
The reason for these risks is not entirely clear, but scientists believe there is a relationship between age, fertility and a healthy pregnancy. A woman is born with all the eggs she'll ever have and researchers theorize that the quality of the egg breaks down as a woman ages, leading her to ovulate eggs later in life that are not as healthy. The major risk in this situation is chromosomal abnormalities. Studies show that genetic risks and incidence of Down syndrome at age 15 are about 1 in 1,500. The incidence of Down syndrome increases as the years go by. At age 40, one in 100 women will have a child with Down syndrome.
Other factors that present higher than normal risk include: A previous child with a chromosomal, brain or spinal cord abnormality or previous genetic condition; those who are carriers of X-linked diseases such as hemophilia; those who are carriers or whose partners are carriers of a known genetic disorder; exposure to dangerous substances during pregnancy, or if an ultrasound indicates a problem.
Q: What can couples do to mitigate this risk?
A: Other than trying to stay healthy and seeing that any chronic medical condition is under control, and taking prenatal vitamins containing at least 0.4 mg. of folic acid, there's really not a lot you can do to mitigate it. Risk factors occur in all ethnic groups. Some studies have advocated taking folic acid prior to pregnancy and certain vitamins to reduce the risk for Down syndrome, but there is no clear conclusion that doing so will prevent a woman from having a baby with Down syndrome.
Q: How can couples decide what screening tests are appropriate?
A: The appropriate screening test depends on the baby's gestational age. One test, a triple screen, is a sophisticated measure that looks at three biochemical markers that are secreted into a woman's blood stream. The woman has to be between 15-20 weeks pregnant for that test. Another test is a fetal ultrasound, performed at 16-18 weeks of gestation. Invasive diagnostics procedures, such amniocentesis and a chorionic villus sampling (CVS) can be performed early in pregnancy. In most cases, insurance picks up the costs of these tests. In any event, the decision to undergo prenatal testing is a personal one.
Q: What do couples do with the results of these tests?
A: For most couples, the results of these tests are reassurance that the pregnancy is progressing normally and they can expect to deliver a healthy baby. However, if the diagnostic tests reveal a chromosomal abnormality or some other abnormal result, then we counsel couples on their options. Other specialists, pediatricians, neurosurgeons, or neurologists, for example, can be consulted so parents can better understand and prepare for any special needs the child will have.
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This information is provided by the Cleveland Clinic and is not intended to replace the medical advice of your doctor or health care provider. Please consult your health care provider for advice about a specific medical condition. For additional written health information, please contact the Health Information Center at the Cleveland Clinic (216) 444-3771 or toll-free (800) 223-2273 extension 43771 or visit www.clevelandclinic.org/health This document was last reviewed on: 12/1/2001
The Cleveland Clinic 2004
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