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← Obstetrics and gynaecology indexChapter sections
Purpose and principlesIndications, selection and cautionsMethod and interpretationClinical next stepsProcedure and medicine safetyRisks, monitoring and follow-upSpecial situationsCommon pitfallsQuestionsSources
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Educational draft · awaiting clinical reviewThe full textbook explains uncertainty but does not replace live national or local guidance, specialist advice, or current prescribing information.

Preterm labour assessment

Obstetrics and gynaecology · UK scope · Sources checked 7 Sept 2026 · Clinical review pending

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Possible imminent preterm birth or maternal emergency

Progressive contractions with cervical change, significant bleeding, infection, fetal compromise or a prolapsed cord requires urgent maternity assessment.

Action: Assess maternal and fetal condition, establish gestation and membrane status, call senior obstetric and neonatal staff and start indicated optimisation while deciding whether transfer or immediate birth is safest.

Purpose and principles

Distinguish symptoms suggesting early labour from established birth or another emergency, select an appropriate diagnostic pathway and initiate gestation-specific neonatal protection without avoidable delay.

Symptoms such as tightenings, pelvic pressure, backache, cramps or a change in discharge are common and do not all predict birth. They nevertheless deserve a structured maternity assessment before 37 weeks because intervention may be time sensitive. Establish gestation from reliable dating, singleton or multiple pregnancy, previous spontaneous preterm birth, cervical surgery, current prophylaxis and the pattern of symptoms. Ask specifically about bleeding, fever, fluid leakage and fetal movement. Determine whether the clinical priority is threatened labour, established labour, ruptured membranes, infection or a separate abdominal emergency.

Examination is purposeful. Record observations and abdominal findings, assess fetal wellbeing at an appropriate gestation and offer a sterile speculum examination. A visibly dilated cervix, exposed membranes or fluid pooling changes the pathway. Avoid repeated digital examinations when membrane rupture is possible; if a diagnostic swab is indicated, obtain it before digital examination and according to the assay instructions. Established labour means progressive cervical dilatation with regular contractions, not simply a positive biomarker. Predictive testing must not hold up care when birth is visibly progressing.

Indications, selection and cautions

Progressive symptoms

Increasing contraction frequency with pelvic pressure or cervical change is more concerning than brief isolated tightenings that settle.

Possible membrane rupture

A gush or persistent trickle of clear fluid redirects assessment toward PPROM and changes the value and suitability of threatened-labour biomarkers.

Infective trigger

Fever, urinary symptoms, uterine tenderness or offensive discharge can indicate infection that needs treatment and may make tocolysis unsafe.

High-risk obstetric history

Previous early spontaneous birth, mid-trimester loss or substantial cervical surgery lowers the threshold for specialist involvement without proving current labour.

Red flags requiring action

  • Fever with uterine tenderness, offensive fluid or maternal deterioration raises concern for infection and makes delaying birth potentially harmful.
  • Heavy bleeding, persistent severe pain or an abnormal fetal heart rate requires evaluation for abruption or another emergency before considering tocolysis.

Method and interpretation

  1. 01
    Clinical assessment and sterile speculum examinationFirst step
    Why
    Assess the cervix, bleeding and fluid while identifying established labour or another urgent problem.
    Interpretation and limitations
    A clear clinical emergency supersedes prediction tests; obtain relevant samples before digital examination and avoid unnecessary repeated vaginal examinations.
  2. 02
    Transvaginal cervical length from 30+0 weeks
    Why
    Assess the likelihood of birth within 48 hours in symptomatic intact-membrane pregnancy.
    Interpretation and limitations
    A length of 15 mm or less supports diagnosed preterm labour; a longer measurement reduces risk but does not cancel new or worsening symptoms.
  3. 03
    Available validated threatened-labour biomarker
    Why
    Support risk assessment when the relevant service pathway calls for a biochemical test.
    Interpretation and limitations
    Use NHS England's interim Actim Partus pathway where implemented after fFN discontinuation; check sampling restrictions and do not substitute a membrane-rupture assay with a similar name.
  4. 04
    Urine culture and targeted infection tests
    Why
    Investigate urinary or genital infection when symptoms or clinical findings make it plausible.
    Interpretation and limitations

Clinical next steps

01First assessmentIdentify whether delay is safeFirst stepA patient before 37 weeks reports symptoms compatible with early labour.+
  1. 1Establish dating, observations, symptom progression and fetal wellbeing, and assess for bleeding, infection, membrane rupture or cord prolapse.
  2. 2Perform a consented speculum examination and collect appropriate samples, then decide whether the patient has established labour or requires further risk assessment.
  3. 3Treat maternal illness and arrange urgent delivery where necessary before considering medicines intended to prolong pregnancy.
02DiagnosisUse the gestation-appropriate exclusion pathwayMembranes are intact and no immediate maternal or fetal emergency is present.+
  1. 1At 29+6 weeks or less with clinically suspected labour, start the indicated preterm-labour pathway rather than waiting for a reassuring biomarker.

Procedure and medicine safety

Briefly reduces contractions to allow fetal maturation treatment or safe in-utero transfer in selected intact-membrane labour.

Nifedipine for short-term tocolysis

Prescribe oral nifedipine under the maternity unit's defined immediate-release or modified-release loading and maintenance regimen, with an explicit maximum dose and usually a 48-hour stop point; formulations and schedules are not interchangeable.

This indication is off label. Record blood pressure and pulse, avoid clinically important hypotension and conditions requiring delivery, and review combined vasodilator or magnesium treatment.

Provides a licensed oxytocin-receptor antagonist option within its gestational and clinical eligibility criteria.

Atosiban when nifedipine is contraindicated

Give 6.75 mg intravenously over 1 minute, then infuse 18 mg/hour for 3 hours followed by 6 mg/hour for up to 45 hours; the course must not exceed 48 hours and preferably not 330.75 mg total.

Do not use to delay delivery with fetal compromise, significant haemorrhage, abruption or suspected intrauterine infection; check the SmPC restrictions including placenta praevia and membrane rupture.

Risks, monitoring and follow-up

  • Reassess contraction pattern, pain, observations and fetal status while deciding whether the initial threatened-labour assessment is evolving into established labour.
  • Monitor maternal haemodynamics during nifedipine or atosiban and stop or review treatment if hypotension, respiratory symptoms or new contraindications develop.
  • Record every optimisation dose and time, especially before transfer, so the receiving unit can continue accurately without duplicate loading doses.
  • If discharge is agreed after low-risk assessment, give direct maternity contact details and instructions to return for persistent or recurrent contractions, fluid loss, bleeding or reduced movement.
  • Review subsequent culture results and arrange specialist follow-up when an early presentation or previous obstetric history identifies ongoing prevention needs.

Special situations

Two cervical thresholds answer different questions

A 25-mm cervix during mid-trimester screening identifies prevention risk, whereas 15 mm in symptomatic later pregnancy is used to estimate imminent birth.

Actim names are not interchangeable

Actim Partus assesses threatened preterm birth in an appropriate intact-membrane pathway; tests intended to detect amniotic fluid address a different diagnostic question.

Positive risk does not mandate induction

A positive threatened-labour test supports observation, optimisation and the correct birth setting, but is not itself a reason to end an otherwise safe pregnancy.

A negative test has a context

Sampling outside the validated population or ignoring a new clinical deterioration can make an apparently reassuring result unsafe to act on.

Common pitfalls

  1. 01

    Ordering discontinued fFN cassettes as though they were reliably available and allowing the request to delay indicated treatment.

  2. 02

    Confusing the 15-mm symptomatic diagnostic threshold with the 25-mm preventive screening threshold.

  3. 03

    Using a biomarker result to overrule obvious cervical progression, ruptured membranes or signs of intrauterine infection.

  4. 04

    Prescribing prolonged maintenance tocolysis without an explicit short-term goal, contraindication review or stop point.

Practice

Two practice questions

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Question 1 of 2
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Obstetrics and gynaecologyOriginal SBA

A very early symptomatic presentation

A patient at 28+4 weeks has intact membranes and a clinical assessment suggesting preterm labour. There is no bleeding or infection. Which approach best follows the NICE gestation-based pathway?

Choose one answer, then submit
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Sources and review status5 sources · checked 7 Sept 2026 · clinical review pending+
Sources

Sources and review status

National guidance is shown before implementation-dependent detail. Typical adult dose examples remain subject to patient factors, contraindications and the live BNF or specialist protocol. Source check completed 7 Sept 2026; clinical approval remains outstanding.

  • NICE NG25 diagnostic and treatment recommendations
  • NHS England discontinuation of Hologic fetal fibronectin testing
  • NICE biomarker test recommendations for preterm labour
  • Atosiban infusion UK summary of product characteristics
  • NHS England Saving Babies Lives version 3 care bundle

Editorial contact: Doctor’s Passport editorial team. Source-check date is separate from clinical approval. Report a content problem · Content changes

Authoring stateComplete draftClinical stateAwaiting reviewJurisdictionUnited Kingdom

NICE uses gestation to balance the cost of overtreatment against the consequences of missing very early birth. At 29+6 weeks or earlier, a clinical diagnosis of suspected preterm labour triggers treatment. From 30+0 weeks with intact membranes, an experienced transvaginal cervical-length measurement can help estimate birth within 48 hours: 15 mm or less supports diagnosed labour, whereas a longer cervix reduces the probability and permits consideration of alternative diagnoses and discharge with clear advice. This symptomatic 15-mm threshold is different from the 25-mm mid-trimester prevention threshold.

Operational guidance must reflect test availability. NHS England announced discontinuation of Hologic fFN testing and an interim Actim Partus pathway. Where that pathway applies, a negative result indicates low risk and usually avoids transfer or optimisation solely for threatened birth; a positive result supports care in a suitable unit and indicated medicines, not automatic induction. Follow the test's validated population and avoid using it to override infection, bleeding, membrane rupture or established labour. NICE's older fFN algorithm remains useful only where the specified assay is available: 50 ng/mL or less is negative and above 50 is positive. Do not combine cervical length and fFN simply to keep testing until one becomes positive.

Key points

  • Preterm labour assessment begins with gestation, symptoms, maternal observations, fetal wellbeing and membrane status.
  • A sterile speculum examination can assess fluid, bleeding and cervical appearance; collect any indicated biomarker sample before digital examination.
  • For clinically suspected labour at 29+6 weeks or earlier, NICE advises treatment without waiting for a cervical-length exclusion test.
  • At 30+0 weeks or later with intact membranes, transvaginal cervical length of 15 mm or less supports diagnosed labour; more than 15 mm makes birth within 48 hours less likely.
  • Hologic fFN cassettes have been discontinued: services need the NHS England interim pathway, including Actim Partus where specified, rather than an unavailable test.
  • The legacy NICE fFN threshold is negative at 50 ng/mL or less and positive above 50, but only applies if the correct assay is genuinely available.
  • Nifedipine may briefly delay suitable intact-membrane labour for steroids or transfer; significant infection, bleeding or fetal compromise may contraindicate delay.
Treat identified infection appropriately; neither a normal inflammatory marker nor a negative urine dipstick alone explains away progressive labour.
  • 05
    Fetal monitoring and ultrasound when indicated
    Why
    Assess fetal wellbeing, presentation, growth and neonatal planning needs.
    Interpretation and limitations
    Monitoring should inform an agreed intervention plan appropriate to gestation; at the limits of viability discuss its purpose with senior obstetric and neonatal clinicians.
    • 2
    From 30+0 weeks use expert cervical length when available; apply the 15-mm symptomatic threshold and the current commissioned biomarker pathway when appropriate.
  • 3If labour cannot be excluded because suitable tests are unavailable, manage according to the diagnosed-labour pathway and senior judgement; document the uncertainty and reassessment plan.
    • 03OptimisationPrepare the infant and place of birthPreterm birth is suspected sufficiently strongly to justify treatment or is becoming established.+
    1. 1Offer or consider corticosteroids according to gestation and likelihood of birth, and magnesium neuroprotection when the birth-within-24-hours criteria apply.
    2. 2Assess intact-membrane tocolysis eligibility: NICE considers nifedipine at 24+0–25+6 and offers it at 26+0–33+6; use an oxytocin-receptor antagonist if nifedipine is contraindicated.
    3. 3Coordinate in-utero transfer when the patient is stable and birth is not imminent, and arrange indicated intrapartum antibiotics and neonatal counselling.