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Many women today are waiting until later in life to have children. In the United States, birth rates for women in their 30s are at the highest levels in three decades. However, an older mother may be at increased risk for miscarriage, birth defects, and pregnancy complications such as twins, high blood pressure, gestational diabetes, and difficult labors. Some studies show that while there may be a greater likelihood of pregnancy complications in older women, their babies may not have more problems than babies of younger women. This is more likely when women receive prenatal care and give birth in a healthcare facility equipped to care for high-risk mothers and babies.
The risk of having a baby with chromosomal abnormalities increases with maternal age. Listed below are the risks for having a baby with Down syndrome, one of the most common chromosomal birth defects, as well as the overall risks for having a baby with any type of chromosome abnormality, including Down syndrome:
|Maternal age||Down syndrome||Any chromosome abnormality|
|Under 30 years||Less than 1/1,000||Less than 1/385|
|45 years||About 1/25||1/21|
It is possible that risks may be higher as many statistics only report live births and do not take into account pregnancies with chromosomal abnormalities that were terminated or ended due to natural pregnancy loss. There are approximately 400 different types of chromosome abnormalities that have been observed in humans, however, many are rare. The risk for Down syndrome makes up almost half of the maternal age risk for chromosome abnormalities.
In general, for women under the age of 40, after having one child with Down syndrome, the chance of having another baby with Down syndrome is 1 percent. After age 40, the recurrence risk for Down syndrome is based on the age of the mother at delivery. It is important to know that about 80 percent of babies with Down syndrome are born to women under the age of 35. This is because women under the age of 35 have more babies than women over 35. The physician may refer parents to a genetic specialist or genetic counselor who can explain the results of chromosomal tests in detail, including what the recurrence risks may be in another pregnancy and what tests are available to diagnose chromosome problems before a baby is born.
Prenatal testing is available to help diagnose or rule out chromosomal abnormalities and other genetic birth defects. Testing may include blood tests, ultrasound (using sound waves to look at internal structures), chorionic villus sampling (testing the tissues around the fetus), or amniocentesis (withdrawing a sample of the amniotic fluid).
Some studies have shown a higher chance of miscarriage (early pregnancy loss) in older mothers. When considering all women, about half of first trimester miscarriages occur because of a chromosomal abnormality in the fetus. Because these abnormalities increase with maternal age, miscarriage is also more likely.
If you are pregnant and over the age of 30, talk with your physician about your individual health and discuss plans for helping you and your developing baby maintain a healthy pregnancy.