The implications of fetal fibronectin

A few people have asked me what a positive fetal fibronectin test means. That is an excellent question, and one to which there is not a very clear answer. The manufacturer of the test makes no statistical claims about your likelihood of imminently giving birth after a positive result. In looking around on the internet, it seems that a lot of women are told by their doctors that a positive result means a 30-50% chance of going into labor in the next 2 weeks. Others are told that it's a 15% chance. I don't know where those numbers come from, though. This paper showed that cervical length was a better predictor of imminent labor than fetal fibronectin, and showed that women with a cervix longer than 15 mm (which I still have, barely) only had a 0.6% chance of delivery in the next 7 days.

Both times when I took the test, the doctors who administered it told me beforehand that a positive result meant "nothing." And I guess that's basically true. But I still would have preferred to have a negative result. My OB wants to retest me when I come in for my next appointment on October 12th. It is possible to have a negative result after testing positive. But even a positive result at that point would be a little less scary, because most women will start to test positive at around 33-34 weeks.