Conclusion
Women with CL≤25mm had a significant association with sPTB <34
weeks, which is an important clinical goal for preterm birth.
Additionally, we found that the best cutoff points for all gestational
ages outcomes (<37, <34, <32 and
<28 weeks) are over 25mm. Considering the feasibility to
perform CL measurement following a standard technique and the capability
to detect almost one third of all sPTB <37 weeks, we suggest
to use CL ≤30mm as the cutoff for cervical length to identify women at
risk of sPTB. This is easier to remember and is very similar to the best
cutoff point identified in our study. Thus, women with CL≤30mm should be
recognized as at higher risk for PTB and those with CL≤25mm should be
recognized and treated properly to reduce PTB<34 weeks.
It is important to highlight that although women with CL≤30mm are at
higher risk for PTB, effective treatment for preventing PTB in women
with 25–30mm CL are not available 26. These women
should not be treated with progesterone, cervical pessaries, or cerclage
because these treatments did not show clear benefits in reducing sPTB
but should, however, receive a close antenatal care follow-up.
Considering the cutoff point where vaginal progesterone has demonstrated
efficacy (25mm), the NNS of 248 to detect 18 women with CL ≤25mm is an
acceptable number, which suggests the feasibility of implementing TVU
for pregnant women in mid-trimester in settings like Brazil.
As most PTBs worldwide are concentrated in low- and middle-income
countries, this analysis is important to describe specific results for
our population and stimulate new studies in other similar settings
focused on strategies to reduce PTB. In such countries, where economical
resources are considerably limited, it is important to define with
precision the best strategies to reduce costs while improving health
care. Nowadays, the national antenatal care for Brazil has not adopted
routine TVU at mid-trimester screening based on studies developed in
high-income countries with lower rates of sPTB. The NNS estimated in our
study creates an opportunity to review the Brazilian and other
countries’ protocols to deal with the PTB prevention. The estimated NNS
is considered low and acceptable and should underpin the implementation
of the TVU as a mid-trimester screening test.