Fetal fibronectin is a glycoprotein present in amniotic fluid, placenta and the extra cellular substance of the decidua. Its synthesis and release is increased by the mechanical and inflammatory events which occur prior to the onset of labour. Fetal fibronectin may normally be detected in vaginal secretions up to 20 weeks gestation (at which time the amnion and chorion become fused) and is then normally undetectable until about 36 weeks gestation.
The presence of fibronectin in vaginal secretions between 20 and 36 weeks may be used to predict a risk of preterm labour. Fibronectin testing may be used to assess risk in asymptomatic women at high risk of preterm labour. However, it is in distinguishing 'true' from 'false' preterm labour in symptomatic women that fibronectin testing is probably of most value. While a positive fibronectin test in a symptomatic woman only predicts a risk of preterm delivery within the next 7 days for approximately 40%, a negative fetal fibronectin test reduces the risk to less than 1%. This is a level of risk at which it would be reasonable to withhold in utero transfer and treatment.
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The first trimester is very important for the mother and the baby. For most women it is common to find out about their pregnancy after they have missed their menstrual cycle. Since, not all women note their menstrual cycle and dates of intercourse, it may cause slight confusion about the exact date of conception. That is why most women find out that they are pregnant only after one month of pregnancy.