Skip to textbook content
Doctor’s PassportTextbook
TopicsAll topics

Loading topic navigation…

Textbook navigation
TopicsAll topics

Loading topic navigation…
← Obstetrics and gynaecology indexChapter sections
OverviewAetiologyPathophysiologyClinical features and red flagsInvestigationsDifferential diagnosisManagementComplicationsMonitoring and follow-upSpecial situationsCommon pitfallsQuestionsSources
Full textbook13 sectionsOpen only what you need
Educational draft · awaiting clinical reviewThe full textbook explains uncertainty but does not replace live national or local guidance, specialist advice, or current prescribing information.

Fetal growth restriction

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

RapidFull
!
Reduced movements with suspected placental compromise

Reduced fetal movements, abnormal fetal heart assessment or absent or reversed umbilical artery end-diastolic flow in a growth-restricted pregnancy can indicate significant compromise.

Action: Arrange immediate maternity assessment and senior obstetric or fetal medicine review; evaluate fetal heart status and Dopplers, assess maternal blood pressure and symptoms, and decide whether monitoring, transfer or urgent birth is required.

Overview

Identify pathological failure of fetal growth, combine growth trajectory with placental and fetal assessment, and choose surveillance and birth timing proportionate to deterioration risk.

Fetal growth restriction describes a pathological process, whereas small for gestational age describes a size distribution. Many small fetuses are healthy and some growth-restricted fetuses remain above a conventional size threshold after a substantial fall in growth trajectory. Avoid reducing the diagnosis to a single centile. Establish reliable gestational dating, use the agreed growth standard consistently and inspect abdominal circumference, estimated fetal weight, growth velocity and placental or fetal evidence of compromise. Maternal disease and movements are part of the same assessment rather than separate background information.

Placental dysfunction is a major cause, especially with hypertension, renal disease, vascular diabetes, smoking or a previous affected pregnancy. Early severe restriction also raises concern for fetal anomaly, chromosomal disease or infection. The clinical significance of an abnormal result depends on gestation: an early small fetus with abnormal Dopplers may need prolonged specialist surveillance and neonatal counselling, whereas a near-term fetus with poor growth may be safer delivered. Distinguishing those situations requires prompt referral and a documented plan, not simply another routine growth appointment.

Aetiology

01

Placental insufficiency

Impaired placental development or vascular function can limit nutrient and oxygen transfer, especially with maternal hypertensive, renal, autoimmune or vascular disease.

02

Fetal and exposure causes

Chromosomal or structural abnormalities, selected congenital infections and harmful exposures can impair growth and are especially relevant in early or otherwise unexplained severe restriction.

Pathophysiology

  1. 1
    Reduced substrate transfer

    An inadequate placental exchange surface or abnormal perfusion limits fetal substrate delivery, reducing tissue growth and often abdominal circumference before the full clinical picture emerges.

  2. 2
    Circulatory adaptation

    The fetus redistributes circulation during reduced oxygen availability; different arterial and venous Doppler changes reflect adaptation or more advanced cardiovascular compromise.

  3. 3
    Progressive loss of reserve

    With continuing placental insufficiency, growth restriction can progress to hypoxaemia, acid-base disturbance and reduced tolerance of labour, making timely birth central to management.

Clinical features and red flags

Risk at booking

Previous SGA or stillbirth, hypertensive disease, renal or autoimmune disease, smoking and other placental risk factors should trigger an individual surveillance assessment.

A concerning trajectory

A falling abdominal circumference or weight centile, especially with other evidence of compromise, matters even when the latest estimate is above the tenth centile.

Severe smallness

Estimated weight or abdominal circumference below the third centile warrants particular attention because the probability of pathological restriction is higher.

Maternal-fetal warning signs

Reduced movements, hypertension, pre-eclampsia symptoms, oligohydramnios or abnormal Dopplers intensify concern beyond the size estimate alone.

Red flags requiring action

  • Reduced or changed movements require immediate maternity contact even if the last growth scan was reassuring.
  • Absent or reversed umbilical artery end-diastolic flow requires urgent specialist assessment of fetal condition and the appropriate place and timing of care.
  • Severe maternal headache, visual symptoms, hypertension or epigastric pain alongside poor fetal growth requires assessment for pre-eclampsia.

Investigations

  1. 01
    Dating review and serial ultrasound biometryFirst step
    Why
    Establish accurate gestation and assess fetal size and interval growth.
    Interpretation and limitations
    Use the earliest reliable dating information; redating a late small fetus to make it fit the chart can conceal real growth restriction.
  2. 02
    Umbilical artery Doppler
    Why
    Assess resistance in the placental circulation and identify advanced placental compromise.
    Interpretation and limitations
    Increased resistance and absent or reversed end-diastolic flow change surveillance and delivery planning; normal flow does not eliminate late-onset restriction.
  3. 03
    Amniotic fluid and fetal heart assessment
    Why
    Add evidence about placental function and current fetal condition.
    Interpretation and limitations
    Low fluid or non-reassuring heart-rate findings increases concern, while reassuring results describe present status and require interpretation alongside the trajectory.
  4. 04
    Maternal blood pressure, urine and relevant bloods
    Why
    Investigate pre-eclampsia or maternal disease contributing to placental insufficiency.
    Interpretation and limitations
    Proteinuria, renal or hepatic dysfunction and thrombocytopenia may change the maternal indication for birth independently of fetal measurements.

Differential diagnosis

01

Constitutional smallness

A small fetus with consistent growth, reassuring placental and fetal assessment and no additional risk may be healthy, although continued surveillance is still needed to establish the pattern.

02

Incorrect gestational dating

An inaccurate due date can make an appropriately growing fetus appear small; establish dating from early reliable data rather than adjusting it to a late measurement.

03

Measurement or chart effects

Operator variability, fetal position and use of a different growth chart can change centiles; review raw measurements and methodology before assuming true biological deterioration.

Management

01Prevention and screeningIdentify pregnancies needing growth surveillanceFirst stepAntenatal risk assessment identifies a greater likelihood of placental disease or impaired growth.+
  1. 1Address smoking and maternal disease, and prescribe low-dose aspirin when the applicable pre-eclampsia or placental-risk criteria are met.
  2. 2Arrange serial ultrasound surveillance for higher-risk pregnancies and use symphysis-fundal height appropriately in lower-risk singleton care.
  3. 3Provide clear information about fetal movements and make sure an abnormal measurement produces a booked assessment rather than an untracked recommendation.
02Confirmed concernDefine severity and surveillance intensityBiometry, growth velocity or clinical findings raise suspicion of pathological restriction.+
  1. 1Review gestation, previous measurements and chart consistency, then assess umbilical artery flow, fluid, fetal heart status and maternal condition.

Complications

01

Fetal death and hypoxia

Severe placental insufficiency increases the likelihood of stillbirth and intrapartum compromise, while surveillance and timely delivery aim to reduce exposure to worsening conditions.

02

Consequences of early birth

Necessary preterm delivery can lead to respiratory, feeding and developmental difficulties, so neonatal resources and counselling are important in early-onset disease.

03

Neonatal adaptation problems

Growth-restricted newborns may have difficulty maintaining glucose and temperature and need feeding support, with follow-up tailored to gestation and the underlying cause.

Monitoring and follow-up

  • Review maternal blood pressure and pre-eclampsia symptoms at each clinically relevant contact, especially when placental resistance or growth deteriorates.
  • For FGR identified before 34+0 weeks, NHS England uses umbilical artery Doppler at least every two weeks, with more frequent specialist assessment when indicated; keep biometry at a sufficient interval to assess true growth.
  • Check that the patient can access urgent maternity review and understands that a scheduled scan is not a reason to wait after reduced movements.
  • After birth, discuss placental findings where available, neonatal growth and the recurrence-prevention plan before a future pregnancy.

Special situations

Different Doppler questions

Umbilical artery flow assesses placental resistance; specialist middle cerebral artery and ductus venosus measurements address different aspects of fetal adaptation and deterioration.

Late disease can hide

A normal umbilical artery waveform near term does not rule out placental growth restriction, so trajectory and additional clinical concerns remain important.

Chart update in 2026

RCOG now supports Hadlock, WHO, FMF and GROW standards without choosing one preferred chart; the transition requires careful comparison of previously reported centiles.

Birth route is contextual

Induction with appropriate intrapartum monitoring may be reasonable when fetal condition permits, while severe Doppler abnormalities or compromise may favour caesarean birth.

Common pitfalls

  1. 01

    Equating every fetus below the tenth centile with pathology or dismissing one above it despite marked slowing of growth.

  2. 02

    Repeating weight estimation too soon and interpreting measurement variability as genuine acceleration or deterioration.

  3. 03

    Changing the estimated due date late in pregnancy because the fetus measures small.

  4. 04

    Assuming a normal umbilical artery Doppler or recent normal scan permits delayed review of reduced movements.

Practice

Two practice questions

Your practice draft is saved in this browser.

Question 1 of 2
0 correct
Obstetrics and gynaecologyOriginal SBA

A reassuring Doppler in late disease

At 37 weeks a fetus has crossed down substantially in abdominal circumference, with new oligohydramnios. Umbilical artery Doppler remains normal. Which interpretation is most appropriate?

Choose one answer, then submit
← Rapid synopsisBack to overviewAll Obstetrics and gynaecology topics →
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.

  • RCOG GTG31 small fetus and growth restriction
  • RCOG fetal growth chart update July 2026
  • NHS England Saving Babies Lives care bundle version 3.2
  • NICE NG133 aspirin for pre-eclampsia prevention
  • NICE NG201 fetal growth monitoring

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

Serial biometry should be separated by enough time to distinguish biological growth from measurement error, commonly around three to four weeks for screening and no less than two weeks for growth assessment except specialist circumstances. Dopplers and fetal heart surveillance may need to be much more frequent than weight estimation. A scan report should state the measurements, centiles, comparison dates, liquor assessment and Doppler findings so that another clinician can understand why the plan changed. A reassuring umbilical artery result is valuable but cannot exclude late placental dysfunction.

The July 2026 RCOG update removed INTERGROWTH support following the NHS England decision and describes Hadlock, WHO, FMF and GROW estimated fetal weight standards without preferring one. Use the current locally implemented standard consistently, recognising that a chart change can alter a displayed centile without representing a biological change. Discuss uncertainty openly: ultrasound weight is an estimate, screening does not identify every affected fetus, and growth surveillance does not guarantee prevention of all stillbirths.

Key points

  • Fetal growth restriction means failure to achieve growth potential; it is not synonymous with a weight estimate below the tenth centile.
  • Assess both absolute size and growth velocity, together with Dopplers, amniotic fluid, fetal movements and maternal disease.
  • An estimated fetal weight or abdominal circumference below the third centile raises particular concern even before other abnormalities appear.
  • Umbilical artery Doppler evaluates placental resistance; a normal result does not exclude late-onset growth restriction.
  • Aspirin can prevent placental disease in selected higher-risk pregnancies but does not reverse established fetal growth restriction.
  • The delivery decision weighs the risk of remaining in utero against prematurity and must be updated when maternal or fetal findings change.
05
Detailed anatomy, genetics and infection assessment selectively
Why
Investigate early, severe, unexplained or anomaly-associated growth restriction.
Interpretation and limitations
Fetal medicine selects targeted testing after counselling; a blanket infection screen or genetic test for every small fetus is not automatically informative.
2
Refer early or severe disease and abnormal Dopplers to fetal medicine, with neonatal counselling and an appropriate care location.
  • 3Document what is measured at each review, how soon it occurs and the explicit findings that trigger admission or birth.
    • 03Timing of birthAct when continuing pregnancy becomes riskierA growth-restricted or small fetus approaches a planned decision point or develops additional compromise.+
    1. 1For a singleton with estimated weight below the third centile and no earlier indication, NHS England advises initiating birth at 37+0 weeks and no later than 37+6 weeks.
    2. 2For isolated weight from the third to below the tenth centile without additional concerns, consider birth at 39+0 weeks and achieve it by 39+6.
    3. 3Use specialist earlier timing for abnormal Dopplers, reduced growth, maternal disease or fetal compromise, with steroids and magnesium when indicated but no unsafe delay.
    Key medicines and prescribing safety1 treatment · regimens, roles and cautions+
    Reduces risk in selected pregnancies when begun preventively rather than after severe growth failure is established.

    Low-dose aspirin prevention

    NICE recommends 75–150 mg orally once daily from 12 weeks until birth for qualifying pre-eclampsia risk; a placental-disease pathway may use the RCOG-specific 150 mg nightly schedule to 36 weeks.

    Document which indication and stop point applies; check allergy and bleeding concerns, and do not describe aspirin as a treatment that restores fetal growth.