Study:
First trimester is best time to screen pregnant women for fetal Down’s
syndrome
A new study by researchers for the First- and Second-Trimester
Evaluation of Risk (FASTER) Research Consortium has found that the most
optimal and accurate time to screen pregnant women for the presence of
fetal Down’s syndrome is during the first trimester. The findings
of the study were scheduled to be published as the lead article in the
Nov. 10 issue of the New England Journal of Medicine.
Researchers reported that the combination of nuchal translucency,
an ultrasound measurement of the area behind the fetal neck, and maternal
blood markers measured at 11 weeks gestation results in the detection of
87 percent of cases of Down’s syndrome.
The study also reports that
a combination of first- and second-trimester markers yielded a 96 percent
detection rate for Down’s syndrome at 11 weeks gestation.
Down’s syndrome is a genetic condition that causes delays in physical
and intellectual development and occurs in one out of every 800 births.
The chances of fetal Down’s syndrome increases with increasing maternal
age. Prior to the study’s finding, it has been a standard of care
for physicians to provide screening and/or diagnostic tests for Down’s
syndrome during a woman’s second trimester of pregnancy.
Currently, the most common screening test for Down’s syndrome is
the triple or quadruple screen, a series of three or four blood tests.
The quadruple screen detects approximately 79 percent of cases of Down’s
syndrome and is performed between 15 and 21 weeks of gestation. If a patient
has a positive quadruple screen, an amniocentesis is offered. Amniocentesis
is also commonly offered to women who are age 35 or older at their delivery
date.
“
When we conducted these studies, we wanted to find the most
optimal method to screen pregnant women for the presence of fetal Down’s
syndrome,” said Lorraine Dugoff, MD, associate professor in the CU
School of Medicine’s Department of Obstetrics and Gynecology and
co-author of the study. “It was our goal to study the effectiveness
of first-trimester screening and find the best possible screening test
for Down’s syndrome.”
Dugoff and her FASTER colleagues performed first- and second-trimester
screenings in 38,167 patients nationwide – the largest U.S. study
of first-trimester screening to-date. Dugoff and colleagues at the CU School
of Medicine started a first-trimester prenatal diagnosis program in 2003
and approximately 2,500 Colorado women enrolled in the study.
“
The program became very popular over the last two years,” said Dugoff. “Many
women who are 35 years and older are choosing to have first-trimester screening
or a combination of first- and second-trimester screening instead of amniocentesis.
There are a lot of women out there who want early non-invasive information
regarding the status of their pregnancy and we are hearing from them.”
All of the centers in this study had special training before
they participated. Due to the potential difficulty in measuring the nuchal
translucency, it is critical that all centers that choose to offer this
type of screening undergo specialized training. This type of training is
currently offered through the Maternal Fetal Medicine Foundation.
“
Currently all women are offered a second-trimester screening
test as a standard of care,” added Dugoff. “The
results of this study will have quite an impact because it
will give pregnant women and their physicians more options
for earlier and more effective screening.”
