There is no reliable way to predict whether a woman with a normal pregnancy will go into labor before 37 weeks. After analyzing the properties of cervical mucus, the researchers found that cervical mucus from women who delivered early was different from that of women who delivered later.
This analysis could predict the risk of early labor, potentially allowing doctors to try to intervene earlier to prevent preterm births. The distinctive chemical and mechanical properties of mucus, and how those properties help it to perform many critical roles as part of the body's first line of defense against infection.
Early births are believed to be caused by infections that occur when microbes reach the uterus through the cervical which is made of mucus and normally blocks access to the uterus. Cervical mucus from pregnant women at high risk of early labor was mechanically weaker and more elastic than that of low-risk pregnant women.
Mucus is formed from polymers known as mucins, and the composition and arrangement of these mucins determine how porous the gel is. Researchers collected samples from two groups of patients; the low-risk group included pregnant women and high-risk group included women who went into labor early, between 24 and 34 weeks.
Doctors were able to prevent labor in high-risk women, and the samples were taken after they were stabilized. Researchers tested the ability of negatively charged spheres about 1 micron in diameter to travel through the mucus, and found a small but statistically insignificant difference in porosity between the high- and low-risk samples.
They then decided to do the same test with charged peptide probes, which are small enough to avoid getting stuck in the mucus network but are sensitive to the biochemical modifications of the mucus. With these peptide probes, the researchers found a significant differences in mucus permeability and adhesiveness: The peptides were able to pass through samples from high-risk women much more easily.
Cervical mucus from women at high risk for early labor may be more susceptible to invasion by potentially harmful bacteria and microbes, making it more likely that those women will experience an infection that leads to preterm birth. The altered mucus may be less able to retain healthy immune system components such as antibodies or antimicrobial peptides, which would normally help to combat infection.
Mucins display immunologically active factors that may also lose when the adhesive properties change, this loss of adhesion might be caused by changes in molecular structure of the mucins, in particular, changes in the number and types of sugar molecules that comprise part of their structure.
Measuring the length of cervix is the common way to predict the risk of preterm birth, a shortened cervix is correlated with higher risk, there are also many cases where a shortened cervix does not lead to preterm birth.
Another test involves measuring levels of fetal fibronectin, a material that essentially "glues" the fetal membranes to the uterine wall, in vaginal secretions.
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