tests including measuring the length of the cervix and fetal fibronectin
levels were previously considered to be key indicators of impending
findings propose that these tests fail to identify adequate cases of
tests cannot be used for widespread routine screening of first-time
Two methods of
screening that were thought to be effective in predicting the risk of preterm delivery
in first-time pregnancies
only identified a limited number of preterm births.
According to a
large study by a National Institutes of Health (NIH) research network, these
two methods, one for measuring the length of cervix
and the other for the level of fetal fibronectin
, do not appear suitable for widespread screening.
‘New methods should be deduced to identify impending preterm birth and other adverse pregnancy conditions.’
Probable Factors of Pre-term Births
Previous studies have indicated that the
two signs of impending preterm birth could be:
- short cervix during pregnancy
- presence of fetal fibronectin in the vagina in early pregnancy
is the lower part of the uterus that shortens and dilates during
labor. A short cervix was defined in this study as
less than 25 mm.
glue-like protein that secures the amniotic sac to the inside of the uterus. Fetal fibronectin is considered to be high if the level is 50
ng/mL or greater.
The amniotic sac
fluid-filled membrane that protects the growing fetus. It breaks down and can
be detected in vaginal discharge toward the end of pregnancy.
focused on spontaneous preterm delivery from labor that occurs naturally, and
initiated through a cesarean section or induced labor for medical reasons.
contractions that begin in the uterus before 37 weeks of pregnancy resulting in
the opening of the cervix is defined as preterm labor
pregnancy is carried up to 40 weeks. Preterm labor increases health risks for
Some risk factors for preterm
labor are infections, carrying twins or multiple fetuses, short interval
between two pregnancies, anemia
, inadequate prenatal care, hypertension during pregnancy and excess amniotic fluid.
9,410 pregnant women with a single fetus at eight research
centers in the United States. The study was conducted as part of the
Nulliparous Pregnancy Outcomes Study: Monitoring Mothers-to-Be (nuMoM2b) and
was published in the Journal of the American Medical Association
underwent ultrasound testing
to measure cervical
- 16 to 22 weeks of pregnancy
- 22 to 31 weeks of pregnancy
fibronectin tests were conducted at:
- 6 to 14 weeks of pregnancy
- 16 to 22 weeks of pregnancy
- 22 to 30 weeks of pregnancy
The two common
tests that were used in this study that screened women through their pregnancy
only helped identify a small proportion of the women
who would eventually deliver preterm.
In the test that measures
cervical length at 16 to 22 weeks, shorter cervix was
found in 35 of 439 women (8%) who delivered spontaneously
before the 37th week of pregnancy.
When the test was conducted at 22 to 31 weeks, shorter cervix was found in 94 of 403 women (23.3%) who delivered
fibronectin test at 16 to 22 weeks, fibronectin
levels were higher in 30 of 410 women
(7.3%) who delivered spontaneously before the 37th week.
On testing at 22
to 30 weeks, fibronectin levels were higher in 31 of
384 women (8.1%) who delivered prematurely .
On combining the
results of the two tests, no significant difference in
results was observed.
The researchers thus concluded that irrespective of whether the two tests
were conducted separately or combined, the methods fail to recognize adequate
number of preterm births that is needed to support routine screening of
methods of assessing women in their first pregnancy do not identify most of
those who will later go on to have a spontaneous preterm delivery," said
the study's senior author, Uma Reddy, M.D., of the Pregnancy and Perinatology
Branch at NIH's Eunice Kennedy Shriver National Institute of Child Health and
"There is a
need to develop better screening tests that can be performed early in
pregnancy." Reddy added.
- Uma Reddy et al.Predictive accuracy of serial transvaginal cervical length by ultrasound and quantitative vaginal fetal fibronectin for spontaneous preterm birth among nulliparous women. Journal of the American Medical Association; (2017) Doi:10.1001/jama.2017.1373.
- Fetal fibronectin test - (http://www.mayoclinic.org/tests-procedures/fetal-fibronectin/home/ovc-20201225)
- Preterm labor - (http://www.mayoclinic.org/diseases-conditions/preterm-labor/basics/definition/con-20035359)