Birth Defects

The risk of giving birth to a baby with a chromosomal abnormality when the mother is of advanced maternal age has been widely researched and discussed. Women are choosing to start families later in life and we are observing new risks in pregnancy due to these tendencies.

We know that there are greater risks of certain birth defects when the mother is of age 35 and older at the time of birth of her child. The most common chromosomal abnormalities seen in babies born to women of advanced maternal age are trisomy disorders or disorders where a third copy of a certain chromosome is present.

Each individual possesses 46 chromosomes: 22 pairs of autosomal chromosomes and 1 pair of sex chromosomes. Inheriting an extra chromosome disrupts the mental and physical development of the fetus.

When discussed with your physician or genetic counselor, prenatal screening and fetal trisomy testing  can be used to detect the following trisomy chromosomal abnormalities:

Down syndrome

Karyotype: Trisomy 21
Frequency of diagnosis:
Each year 1 in 700 babies is born with Down syndrome.

  • Eyes that slant upwards
  • Small skin folds may be present on the inner corner of the eyes
  • Small nose and flat nasal bridge
  • Low muscle tone
  • Too much space between the large and second toes

Life Expectancy:

Individuals with Down syndrome may live well into their 50’s while some individuals age into their 70’s. This is a dramatic increase from when the life expectancy was about 9-11 years for these individuals.

Edwards syndrome

Karyotype: Trisomy 18
Frequency of diagnosis:
Each year 1 in 5,000 babies are born with Edwards syndrome. It is common that fetuses with this syndrome do not survive the pregnancy.


  • low birth weight
  • ears that are low-set
  • “rocker bottom” feet, meaning that the feet are rounded at the base
  • cleft lip and palate
  • the presence of an exomphalos (an abdominal wall defect that results in a sac protruding from the abdomen which usually contains the bowels and liver)
  • Hands with overlapping fingers (typically the middle finger overlaps the index finger and the pinky overlaps the ring finger)
  • Severe developmental delays

Life Expectancy:

Girls born with Edwards syndrome tend to have higher rates of survival than boys. A very small number of individuals born with Edwards syndrome live to complete 1 year. However, there are individuals who have lived well into their 20’s with extreme medical care.

Patau Syndrome

Karyotype: Trisomy 13

Frequency of diagnosis:

Each year about 1 in 16,000 babies is born with Patau syndrome. It is common that fetuses with this syndrome do not survive the pregnancy.


  • Extra fingers or toes
  • Coloboma (a hole or split in the iris)
  • Defects of the heart
  • Cleft palate or lip
  • Small head
  • Sloping forehead

Life Expectancy:

Many fetuses with Patau syndrome do not survive the pregnancy. The majority of babies that are born with this syndrome meet a life expectancy of just 2.5 days, with a small percentage of them completing a year of survival.

If you are of advanced maternal age and are trying to conceive, you may schedule a preconception visit with your physician to discuss the likelihood of your child having a chromosomal abnormality and the screening options available to you.

You may also want to meet with a genetic counselor who can provide support as you make decisions about your pregnancy.