Scientists may be one step closer to identifying those at risk of preterm birth.
A new study has found differences in the cervical mucus of women who delivered prior to 37 weeks, compared to those who carried full term.
Specifically, the research published in the journal Scientific Reports identified that mucous from high-risk patients was more "leaky" than cervical mucus in healthy pregnancies.
"During healthy pregnancy, cervical mucus forms a compact, protective 'plug' between the sterile uterus and the colonised vagina, selectively permitting the passage of desirable agents such as nutrients, gases, and immunological factors, while excluding potentially deleterious environmental particles and pathogens." the authors write in their paper.
Between 25 and 40 per cent of preterm births are caused by infections that occur when microbes reach the uterus through the cervical plug.
"Changes in the permeability of this barrier have long been suspected to play a critical role in the etiology of preterm birth," the researchers note.
They analysed the cervical mucous of three different groups of women: 20 ovulating non-pregnant women aged 18–45 years, 22 healthy, low-risk expectant mothers, and 16 high-risk patients. What the researchers found was a difference in "porosity" in the cervical mucous of women in the low and high risk groups.
But what exactly does this mean?
According to the authors, cervical mucous from women at high risk for early labour may be more susceptible to invasion by potentially harmful bacteria and microbes. This could then result in women experiencing an infection, leading to preterm birth. Additionally, for reasons not yet clear, mucous may be less able to hold onto antibodies which would normally help fight infection.
"Mucins display all sorts of immunologically active factors that you may also lose when the adhesive properties change," Ribbeck explained in a statement.
The researchers caution that while it remains unclear whether the changes in the cervical mucus are a cause or consequence of preterm labour, "our findings clearly demonstrate that the biophysical and biochemical properties of cervical mucus from women who deliver preterm are significantly different from those who carry to term."
Given preterm labour affects 18 per cent of pregnancies worldwide and is the leading cause of neonatal death, the study has important implications.
"At present, there is a critical clinical need for predictive diagnostic tools and biomarkers for preterm birth," the authors write.
While measurement of cervical length occurs during routine screenings and that a short cervix is associated with preterm delivery, in many instances women with a shortened cervix do not deliver prior to 37 weeks.
The researchers argue that their finding that the permeability of cervical mucus is correlated with pregnancy risk "may be exploited as a powerful diagnostic resource because of the accessibility of this biological material."
But their hopes go beyond identifying those at risk of preterm birth as part of routine screening for pregnant women.
"If the mucus is thinner or less adhesive than it naturally is, then we can begin to think about factors to add so that we improve its barrier properties," Ribbeck said.