Fetal fibronectin is a protein that your body makes when you're pregnant. It helps glue the sac that your baby grows inside to the wall of your uterus. Doctors can check for fetal fibronectin by taking a swab of your vagina or cervix.1 2
Up to around the 22nd week of pregnancy, fetal fibronectin can be found in your vagina. But it's not normally found after the 22nd week until the last few weeks of pregnancy (around the 37th week). If fetal fibronectin is found in your vagina between the 22nd week and the 37th week, it could be a sign that you are going into labor.
Your doctor or midwife may suggest you have this test if you or they think you might be in labor.
This test can't always prove that you are definitely in labor, but if the result is negative then the test is usually correct.1 If there's no fetal fibronectin in your vagina, you are probably not in labor. If your cervix is closed and hasn't started to shorten or thin out, and you and your baby are both fine, you will probably be able to go home.
Remember, if the test is positive, it doesn't mean for certain that you are in labor. But you will probably be kept in the hospital to see if you start to have contractions.
![]() |
This information is for educational use only, and is not a substitute for prompt professional medical advice. Readers should always consult a physician or other professional for advice and treatment. ©BMJ Publishing Group Limited 2008. All rights reserved. |












