Direct answer
The fetal fibronectin (fFN) test measures a protein in vaginal secretions to help assess the chance of preterm birth in the next 7-14 days, usually between about 22 and 34-35 weeks. The fFN test is most useful when negative, because a negative result makes delivery within two weeks less likely. A positive fFN result raises concern but does not predict delivery.
Key takeaways
- Purpose: The fFN test supports short-term risk assessment for preterm labour, not diagnosis of labour.
- Strength: A negative fFN result has a high negative predictive value over about 7-14 days.
- Limitation: A positive fFN result is a weak predictor on its own; most women with a positive result do not deliver within two weeks.
- Context matters: The fFN result is interpreted alongside symptoms, cervical length on transvaginal ultrasound and obstetric history.
- Sampling matters: Recent intercourse, vaginal examination, bleeding, lubricants or vaginal products can distort the result.
At a glance
| Feature | Detail |
|---|---|
| What is measured | Fetal fibronectin protein in cervicovaginal secretions |
| Sample | Swab from the posterior vaginal fornix or ectocervix |
| Usual gestational window | Approximately 22 to 34-35 weeks; local protocols vary |
| Time for sample collection | A few minutes; the speculum or swab step is usually under five minutes |
| Total visit time | Often 30-60 minutes including assessment, monitoring and counselling |
| Result type | Qualitative positive/negative, or quantitative fFN in ng/mL on some analysers |
| Predicts | Short-term (about 7-14 day) likelihood of spontaneous preterm birth |
| Does not predict | Whether the pregnancy will reach term; fetal wellbeing; infection |
Also known as
- fFN test
- Fetal fibronectin swab
- Preterm labour risk test / preterm labour swab test
- Commonly asked for in India as the "preterm labour test" or "early delivery risk test"
What the fetal fibronectin test is
Fetal fibronectin is a protein present where the amniotic sac meets the uterine lining. Small amounts can appear in vaginal secretions in early pregnancy and again as labour approaches at term. When the membranes and decidua are disturbed in mid to late pregnancy, more fetal fibronectin can leak into cervicovaginal fluid.
The fFN test detects this protein on a swab. Some laboratories report simply positive or negative against a threshold; others report a quantitative concentration in ng/mL, which allows risk to be graded rather than treated as yes or no. Reporting format and thresholds depend on the analyser and protocol used by the unit.
Why the fetal fibronectin test is done
- To assess short-term risk in a woman with symptoms suggesting threatened preterm labour, such as tightenings, low backache or pelvic pressure.
- To support decisions about admission, transfer to a unit with neonatal intensive care, antenatal corticosteroids, magnesium sulphate for neuroprotection or tocolysis to allow time for those treatments.
- To reduce unnecessary intervention when the result is negative and the clinical picture is reassuring.
- To add information to cervical length measurement and history in women already considered at higher risk.
Results vary depending on individual clinical circumstances.
Who should get this test
- Women between roughly 22 and 34-35 weeks with symptoms of possible preterm labour and intact membranes.
- Women with a history of spontaneous preterm birth or late miscarriage who develop symptoms.
- Women with a short cervix on ultrasound in whom the clinician wants additional short-term risk information.
The fFN test is generally not appropriate when: membranes have ruptured, there is significant vaginal bleeding, the cervix is already dilated with established labour, cerclage is in place in some protocols, there has been recent intercourse or vaginal examination, or gestation falls outside the validated window. In advanced labour the test adds nothing, management is clinical.
What the fetal fibronectin test cannot detect or exclude
- It does not diagnose labour. Labour is diagnosed clinically, by contractions and cervical change.
- A negative result does not exclude preterm birth. It lowers the probability over the next one to two weeks. Some women with a negative fFN result still deliver early.
- A positive result does not mean delivery is coming. Most women with a positive fFN result do not give birth within two weeks.
- It says nothing about fetal wellbeing, growth, placental function, amniotic fluid volume or fetal heart rate.
- It does not detect infection, chorioamnionitis, bacterial vaginosis, urinary tract infection or sexually transmitted infection.
- It does not detect ruptured membranes. Different tests and clinical assessment are used for that.
- It does not assess the cervix. Cervical length needs transvaginal ultrasound.
- It does not cover multiple pregnancy well. Performance data in twins and triplets are more limited and results should be interpreted cautiously.
If symptoms continue or worsen after a normal or negative result, return to your obstetric team rather than waiting for a scheduled appointment.
Related but different examinations
| Test | Question it answers | How it differs from fFN |
|---|---|---|
| Transvaginal cervical length ultrasound | Is the cervix shortening? | Structural measurement; often used with or instead of fFN, and is the preferred first assessment in many units for asymptomatic high-risk women |
| Phosphorylated IGFBP-1 or placental alpha-microglobulin-1 (PAMG-1) biomarker tests | Is a different membrane-derived protein present? | Alternative biomarkers with their own thresholds and evidence base; not interchangeable with fFN |
| Tests for rupture of membranes | Have the waters broken? | Answers a different clinical question; ruptured membranes invalidate fFN |
| Cardiotocography (CTG / NST) | How is the fetal heart responding, and are there contractions? | Monitors fetus and uterine activity; gives no information on preterm birth risk biomarkers |
| High vaginal swab and urine culture | Is there infection? | Microbiological, not predictive |
| Obstetric ultrasound (growth and wellbeing) | How is the baby growing? Where is the placenta? | Separate examination, performed under PC-PNDT Act 1994 rules in India |
Which test comes first depends on the clinical problem. In a symptomatic woman at 28 weeks, clinical assessment and CTG usually come first, then cervical length and/or fFN. In an asymptomatic woman with a previous preterm birth, cervical length surveillance is the usual pathway. No single test is universally superior, they answer different questions.
How to prepare
Preparation instructions are operational and vary between hospitals and laboratories. Your unit's written instructions take precedence over anything here.
- Avoid intercourse for about 24 hours before the test, where planned in advance.
- Avoid vaginal douching, creams, pessaries, gels or lubricants before sampling, as these can interfere with the assay.
- Tell the clinician about bleeding or spotting, any recent vaginal examination, any recent ultrasound using vaginal gel, suspected leaking of fluid, cerclage or vaginal progesterone use.
- The swab is taken before any digital vaginal examination whenever possible.
- Do not stop or change progesterone, nifedipine or any other prescribed medicine to prepare for this test. Speak to the prescriber first.
If you are using vaginal progesterone
Vaginal preparations may affect the sample. Mention the timing of your last dose; the team may schedule the swab accordingly. Do not skip doses without instruction from your prescriber.
If you have a cervical stitch (cerclage)
Some protocols avoid fFN testing with cerclage in place because interpretation is less clear. Follow your unit's policy.
If you are bleeding or think your waters have broken
Do not wait for a swab appointment. Contact your maternity unit immediately; these situations need direct assessment.
What happens during the test
The clinician explains the procedure and takes consent. A speculum may be used, or the swab may be taken without one depending on the kit. A sterile polyester swab is held against the posterior vaginal fornix or ectocervix for a short period, usually around 10 seconds, then placed in the transport buffer.
Sample collection itself takes a few minutes and is usually described as mildly uncomfortable rather than painful. Bedside cartridge analysers can produce a result quickly; laboratory-based testing takes longer. Turnaround varies by unit: ask the team looking after you when your result will be available and who will discuss it with you.
Understanding your report
The fFN report is usually a single line: positive or negative, or a concentration in ng/mL.
- Negative fFN: fetal fibronectin was not detected above the laboratory's threshold. This lowers the likelihood of spontaneous birth in the next one to two weeks and often supports outpatient management, provided the clinical picture agrees.
- Positive fFN: fetal fibronectin was detected above the threshold. This indicates higher risk than a negative result, but the majority of positive results are not followed by delivery within two weeks. The result is used as one input into decisions about admission, steroids and transfer.
- Quantitative fFN: where a concentration is reported, higher values generally correspond to higher risk. The thresholds used for banding risk are specific to the assay and protocol, so read the value only against the interpretation your unit provides.
"Not detected" is not the same as "excluded". No fFN result, positive or negative, diagnoses or rules out preterm labour. Interpretation must be done in clinical context by the obstetrician caring for you.
When fetal fibronectin results can be misleading
Causes of falsely raised or false-positive results
- Intercourse within about 24 hours (semen can contain fetal fibronectin)
- Digital vaginal examination or transvaginal scan before the swab
- Vaginal bleeding or blood contamination of the swab
- Lubricants, soaps, disinfectants, vaginal creams or pessaries
- Cervical manipulation, recent cerclage or membrane disruption
- Sampling outside the validated gestational window, including near term when fFN rises physiologically
Causes of falsely lowered or false-negative results
- Inadequate contact time or a poorly placed swab
- Very scanty secretions
- Sample handling or transport errors, or delay before analysis
- Rapidly progressing labour where clinical signs outpace the biomarker
Situations where the test performs less predictably
- Twin and higher-order pregnancies
- Ruptured membranes
- Established labour with cervical dilatation
- Asymptomatic women, where the test adds less than cervical length measurement
Risks and safety
Swab-only sampling
Taking a cervicovaginal swab is a low-risk procedure. Possible effects are brief discomfort, a sensation of pressure and occasionally light spotting. It does not involve needles, radiation or medicines.
Sampling with a speculum
Speculum insertion can cause more discomfort and, uncommonly, minor spotting, particularly if the cervix is friable. Tell the clinician if you have pain during insertion.
Risks that follow from the result rather than the test
The main potential harms relate to how a result is acted upon, unnecessary admission, transfer or medication after a positive result, or false reassurance after a negative one. This is why the fFN result is always combined with symptoms, examination and ultrasound. Results vary depending on individual clinical circumstances.
Red flags
Emergency: go to the nearest maternity unit now
- Heavy vaginal bleeding, or bleeding with severe abdominal pain
- A gush or steady leak of fluid from the vagina
- Regular painful contractions before 37 weeks, or a feeling of pressure as if the baby is coming
- Reduced or absent fetal movements
- Severe headache with visual disturbance, upper abdominal pain, or sudden swelling of face and hands
- Fever with abdominal tenderness or foul-smelling discharge
- Fainting, breathlessness at rest, seizure or collapse
Same day: contact your obstetric team today
- Irregular tightenings that are increasing in frequency
- New or increasing watery discharge without a clear gush
- Light spotting after the swab that does not settle
- Burning on passing urine, or new pelvic pain
- Persistent low backache that is new for you
Routine appointment
- Questions about a result you have already been told is negative, with no new symptoms
- Mild discomfort after sampling that has settled
- Planning discussion about repeat testing or cervical length surveillance
Special situations
Twin and multiple pregnancy
Evidence for fFN in multiple pregnancy is more limited, and predictive performance is generally weaker. The result is interpreted alongside cervical length and clinical findings.
Previous preterm birth or late miscarriage
Women with this history are often placed on a surveillance pathway that emphasises cervical length. The fFN test may be added if symptoms develop.
Suspected ruptured membranes
The fFN test is not the right test. Assessment for rupture of membranes and infection takes priority.
Bleeding in pregnancy
Blood interferes with the assay and bleeding itself needs evaluation for causes such as placental abnormality. Address the bleeding first.
Cervical cerclage or vaginal progesterone
Both can affect sampling and interpretation. Tell the team and follow unit protocol; do not alter prescribed progesterone yourself.
Adolescent and older mothers
Age alone does not change how the swab is taken or how the result is read. Overall preterm birth risk differs by other factors, and the clinical plan is individualised.
The fetal fibronectin test in the Indian context
- Burden: Preterm birth is a major contributor to neonatal mortality in India, and India carries a large share of the global preterm birth burden. Figures are published by national and multi-agency sources including the National Family Health Survey and WHO-linked preterm birth estimate reports; check the current edition for the latest numbers.
- Availability: Bedside fFN analysers are mainly available in tertiary hospitals and larger private maternity units. In many centres, cervical length measurement by transvaginal ultrasound is the more accessible and widely used assessment.
- Terminology: Patients often ask for the "preterm labour test" or "early delivery test"; in reports it may appear as fFN or fetal fibronectin, qualitative or quantitative.
- Regulation: Any ultrasound performed during pregnancy in India, including cervical length assessment, is governed by the PC-PNDT Act 1994. Sex determination is prohibited. Consent, record-keeping and form requirements apply.
- Related clinical factors: Anaemia, including iron-deficiency anaemia and thalassaemia trait, and reproductive tract infections are common in Indian antenatal populations and are independently relevant to preterm birth risk. These need their own assessment; fFN does not detect them.
- Data protection: Any online form, report portal or risk calculator handling your details is subject to the Digital Personal Data Protection Act 2023.
- Advertising rules: Claims about preventing preterm birth are restricted under the Drugs and Magic Remedies (Objectionable Advertisements) Act 1954, be cautious of products marketed to "stop early delivery".
Cost and insurance in India
Costs differ widely between government hospitals, trust hospitals and private corporate facilities, and between bedside cartridge testing and laboratory testing. Price bands change over time, so ask for a written estimate before the test rather than relying on published figures. Costs quoted anywhere online should be treated as indicative only.
Factors that influence the price:
- Bedside single-use cartridge versus laboratory immunoassay
- Qualitative versus quantitative reporting
- City, hospital tier and whether the test is imported-kit dependent
- Whether the test is bundled with consultation, CTG, cervical length scan or admission
- Outpatient versus inpatient billing, and emergency versus routine timing
- Repeat testing if symptoms recur
Insurance: Outpatient investigations are often not covered under standard Indian indemnity health policies, whereas tests done during a covered admission may be reimbursed. Maternity benefits usually have waiting periods and sub-limits. Confirm coverage with your insurer or the hospital's insurance desk before testing.
Myths and facts
| Myth | Fact |
|---|---|
| A positive fFN result means the baby is coming soon | Most women with a positive fFN result do not deliver within the next two weeks. The result signals higher risk, not an imminent birth. |
| A negative fFN result guarantees a term delivery | A negative result lowers short-term probability only. It does not predict the rest of the pregnancy, and it does not exclude preterm birth. |
| The fFN test can prevent preterm labour | The fFN test is an assessment, not a treatment. It may help time interventions such as antenatal corticosteroids. |
| The fFN swab can trigger labour | Taking a swab is not known to start labour. Discomfort and occasional spotting are the usual effects. |
| Every pregnant woman should have an fFN test | The test is used in selected situations, chiefly symptomatic women within the validated gestational window. Routine testing of asymptomatic women is not standard. |
| fFN and cervical length measure the same thing | One is a biochemical marker, the other a structural measurement. They provide complementary information. |
Frequently asked questions
How long does the fetal fibronectin test take from start to finish?
The swab takes only a few minutes. The whole visit usually runs 30 to 60 minutes because it includes history, examination, often CTG monitoring and a discussion of the result. Analysis time depends on whether the hospital uses a bedside analyser or a central laboratory, so ask your unit.
Does the fetal fibronectin test hurt?
Most women describe mild pressure rather than pain. A speculum, if used, can be more uncomfortable. Light spotting afterwards is possible. Tell the clinician if you feel pain during the procedure so that the technique can be adjusted or the examination paused.
Can the fetal fibronectin test be repeated?
Yes. If symptoms settle and then return later, a repeat fFN test may be considered while gestation remains within the validated window. The decision depends on your unit's protocol, your symptoms and what cervical length assessment shows. Repeat testing is not automatic.
What is the difference between the fFN test and a cervical length scan?
The fFN test measures a protein in vaginal secretions; a transvaginal cervical length scan measures the cervix itself in millimetres. They answer different questions and are often used together. In India, any obstetric ultrasound is performed under PC-PNDT Act 1994 requirements.
Can intercourse affect my fetal fibronectin result?
Yes. Semen can contain fetal fibronectin and may push a result towards false-positive, so intercourse within roughly 24 hours before testing is usually avoided. Vaginal examinations, lubricants, douching and bleeding can have a similar effect. Tell your clinician about anything recent.
If my fFN test is negative, can I stop worrying about preterm labour?
A negative result is reassuring for the next one to two weeks, but it does not cover the whole pregnancy and does not exclude early birth. Continue your antenatal care, and contact your maternity unit promptly if contractions, bleeding or fluid leakage develop.
Is the fetal fibronectin test useful in twin pregnancy?
Evidence in twins is more limited and predictive performance is weaker than in singleton pregnancy. Some units still use the fFN test in twins as one input, always interpreted alongside cervical length, symptoms and obstetric history rather than as a standalone answer.
What happens if my fFN result is positive?
Your obstetrician reassesses you clinically, may arrange cervical length measurement and fetal monitoring, and considers admission or transfer to a unit with neonatal intensive care. Antenatal corticosteroids, magnesium sulphate or tocolysis may be discussed. Management is individualised and a positive result alone does not decide it.
Who should not have a fetal fibronectin test?
The fFN test is generally avoided with ruptured membranes, significant vaginal bleeding, established labour with cervical dilatation, recent intercourse or vaginal examination, and outside the validated gestational window. Some units also avoid it when cerclage is in place. Your obstetric team will decide suitability.
Sources
- National Institute for Health and Care Excellence, guideline on preterm labour and birth (check current edition)
- Royal College of Obstetricians and Gynaecologists, guidance on the care of women presenting with suspected preterm labour
- American College of Obstetricians and Gynecologists, practice guidance on prediction and management of preterm birth
- Federation of Obstetric and Gynaecological Societies of India (FOGSI), good clinical practice recommendations on preterm labour
- Pre-conception and Pre-natal Diagnostic Techniques (Prohibition of Sex Selection) Act, 1994, Government of India
- Digital Personal Data Protection Act, 2023, Government of India
- World Health Organization, recommendations on interventions to improve preterm birth outcomes
