Advanced Maternal Age is a term applicable
to a woman who will be 35 years of age or older at time
What is the significance of advanced maternal age?
All of the genetic reproductive material (eggs) that a woman
has for conception is present at the time of birth. After
the age of 35, the risk of having a genetically abnormal
conception (fetus or child) increases, and is significant
enough to warrant genetic counseling and contemplation of
diagnostic procedures during pregnancy. These procedures
evaluate fetal chromosomes (karyotype).
The most common diagnostic
procedures performed during pregnancy for evaluation of
fetal karyotype are chorionic villus sampling (CVS) and
What are chromosomes?
Chromosomes are inherited biological material present in
all of the cells of the human body. Genetically normal individuals
have 46 chromosomes (23 pairs) in each cell, half of which
are inherited from each parent.
Chromosomal abnormalities occur when an abnormal number
of chromosomes are inherited from a parent, when one or
more of the 23 chromosomes inherited from a parent have
a structural abnormality, when there is abnormal pairing
of the sets of 23 chromosomes inherited from each parent,
or when random errors in cell division occur near the time
of conception. The overwhelming majority of chromosomal
abnormalities is not inherited and can not be caused by
environmental exposures during pregnancy. Chromosomal abnormalities
can occur in anyone’s pregnancy but the risk increases
with a woman’s biological age.
Other risks associated with AMA
With increasing maternal age there is an increased risk
of medical complications that may have adverse effect on
pregnancy. Examples include hypertension, endocrine disorders
such as diabetes and thyroid disease, rheumatologic disorders
such as lupus, pulmonary and cardiac disease, gynecological
abnormalities such as fibroids, and rarely malignancies.
Additionally there is an increased risk of adverse obstetrical
outcome, especially in a first pregnancy, including glucose
intolerance, hypertensive disease, and complications associated
with preterm birth. Apart from fetal chromosomal abnormalities
there is an increased risk of congenital malformations especially
after the age of 40. These malformations are not detected
by CVS or amniocentesis testing.
Testing options available for AMA
It is considered standard of care to offer all patients
of advanced maternal age prenatal diagnostic evaluation
of fetal karyotype by either CVS or genetic amniocentesis.
These procedures are not without some degree of risk therefore
genetic counseling regarding age specific risks of chromosomal
abnormalities and the available diagnostic or screening
options is recommended for all patients. Screening tests
may reduce the risk of chromosomal abnormalities but do
not exclude them. Regardless of fetal karyotype or maternal
screening results additional testing for AMA should include
detailed ultrasound assessment for fetal congenital abnormalities
at 18-20 weeks of gestation.