Saliva test for risk of preterm birth

This was an interesting article in the British Journal of Obstetrics and Gynecology. (If you can’t read the study, you may have to register, but it’s free.)

An exploratory study to be published in BJOG, has shown that women going into early preterm labour (before 34 weeks gestation) have low-levels of progesterone in their saliva as early as 24 weeks, and that moreover, these levels fail to rise during pregnancy in the normal way. This offers the possibility of developing a simple, non-invasive test to identify women at increased risk of delivering early.

The study was a small one (less than 100 women), and all of the women had at least one risk factor for preterm birth.

The results show that the concentration of progesterone in the saliva of women delivering after spontaneous labour before 34 weeks was significantly lower than those giving birth at term (after 37 weeks) at all gestational ages from 24 weeks onwards.

I presume that a larger study will soon be undertaken to confirm and strengthen these results, and perhaps to see if they are applicable to a general population. If so, I wonder how much it would cost to test everyone, or just those considered at risk. And also, how accurate it is (false positive and false negative rate), and what benefits might exist from finding out that this test predicts you will be having your baby early.

Not having the study as such (it’s restricted to paying subscribers), it’s possible that it’s not highly accurate. For example, let’s say that the average progesterone rate of women giving birth prior to 34 weeks was 10, while the average rate for 34-37 weeks was 15, and the average for 37 weeks+ was 20. Sounds good; but if the range of progesterone of women giving birth prior to 34 weeks was 7-14, and that for 34-37 weeks was 12-18, and that for 37 weeks+ was 16-25, then you see that there is quite an overlap there. If there is no overlap between the groups, then that would be more accurate. And another factor would be what benefits there are — which might be significant, because if you’re at high risk of giving birth prior to 34 weeks, you may be given steroids to mature your baby’s lungs much earlier than you otherwise would, which would probably increase your baby’s chances of surviving and decrease his hospital stay. Some women only realize that they are at risk for a preterm birth when they suddenly go into labor at 33 weeks; doctors may try to delay labor long enough to mature the baby’s lungs, but often that is not possible. If these at-risk women could be given steroids starting at 32 weeks, rather than waiting until they’re already in preterm labor, then that could be highly beneficial. Or, even better, to stop labor altogether until the baby is mature.

This is speculative on my part, but it’s a good and positive speculation. It’ll be interesting to see how it will ultimately work out.


2 Responses

  1. Saw though where they think steroids and anti-contraction(what do you call that) medications may actually cause problems neuro etc. So early steriods in large groups may not be so safe…not sure. So many studies to be done!

    Another test for women…eek! But if there is a way to treat early and avoid preterm labor, that’s good. I wonder how this might impact pre-ecclampsia etc.

    • Yeah, there are always bound to be upsides and downsides. Anti-contractions – tocolytics; steroids in large groups – I have a faint memory of that since you brought it up. However, I’m aware that the logo for the Cochrane Collaboration came from the studies that showed that giving fetuses at risk of preterm birth steroids prior to their birth improved their outcomes (reduced mortality, I’m pretty sure; if not that, then at least reduced NICU stays and what-not) — but that doctors weren’t giving these drugs, and lots of babies died (or were harmed) because they didn’t know that almost every study showed a tremendous improvement for babies. That was the impetus for the Cochrane Collaboration – to look at all the studies and combine the data and get the “best evidence” in one place. It may be that there are more downsides to steroids now, but at the time the benefits were very strong.

      The good news about this test, at least, is that it is minimally invasive — no needles, just spit in a container.

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