Most women over 35 can look forward to having a successful pregnancy and a healthy baby.
Current medical care now enables women in their late 30s and 40s to have safer pregnancies than ever before. Still, it is important to be aware that there is a higher risk of problems related to older age. These include changes in fertility, a higher risk of miscarriage, and increased odds of pregnancy complications, such as high blood pressure, diabetes, and placental problems. The chance of having a child with a chromosomal disorder also rises with maternal age.
Chromosomes are the microscopic packages of genes inside every cell of our body. Normally, each cell has 46 chromosomes inherited in 23 pairs. Sperm and eggs are specialized cells that each carry 23 chromosomes until they join to form the first cell of an embryo. The embryo will then have 46 chromosomes in every cell thereafter. As woman age, so do their eggs. As eggs age, they are more likely to make a mistake in the number of chromosomes they package. Therefore, as a woman gets older, her chances increase of conceiving a baby that receives an incorrect number of chromosomes. This is why women over 35 are given the option of pursuing prenatal diagnosis for chromosome disorders.
Most chromosome abnormalities are accidents of nature. No one can control whether an egg or sperm has the wrong amount of chromosomal material. Miscarriages are often the result of a chromosome abnormality in the embryo fetus. The most common chromosomal disorder in newborns is Down syndrome. Down syndrome happens when a baby receives three copies of the 21st chromosome instead of the normal two copies. Another name for the presence of three chromosomes is trisomy, so Down syndrome is also called trisomy 21. The severity of a chromosome abnormality depends on which chromosome is extra or missing. Other chromosome disorders more common with increasing age include trisomy 13 (Patau syndrome) and trisomy 18 (Edwards syndrome).
Women over 35 have several prenatal testing options. Ultrasound, done at the appropriate time and by a skilled sonographer, can detect many birth defects. One must understand that a normal ultrasound does not, however, rule out all abnormalities. In particular, ultrasound cannot always detect a chromosomal disorder.
The Expanded AFP test is a screening blood test available to all women between 15 and 20 weeks of pregnancy. This test measures amounts of certain substance in the maternal blood during pregnancy and calculates a risk for spina bifida (not associated with age), Down syndrome and trisomy 18. This test is not a diagnostic test, meaning that it does not show whether the fetus is affected or not affected by any of these conditions. The test is also able to screen for all possible chromosome abnormalities. More definitive testing is available by amniocentesis or chorionic villus sampling (CVS).
Prenatal diagnosis can be performed by amniocentesis or CVS. These tests are the most accurate methods for ruling out chromosome abnormalities. Amniocentesis is usually performed between 15 and 20 weeks pregnancy. CVS is done earlier, around 11-12 weeks. Both these test are associated with a small risk of complication. Women should be seen by a genetic counselor prior to deciding to have amniocentesis or CVS. This is because the decision to test necessitates an understanding of the benefits, limitations and risks involved in these tests. At the time of counseling, questions and concerns about family history can be explored and other genetic testing may be offered.
Having prenatal diagnosis can give you peace of mind, as the odds are in your favor: Approximately 95 percent of women over the age of 35 who pursue prenatal testing get normal results.