[CG] Fetal Growth Restriction risk assessment, pregnancies at risk of FGR

Warning

exp date isn't null, but text field is

Risk assessment, prevention and surveillance of pregnancies at risk of fetal growth restriction

(Based on Element 2 of the Saving Babies’ Lives Versions Two, Care Bundle for Reducing Perinatal Mortality)

There is strong evidence to suggest that Fetal growth restriction (FGR) is the biggest risk factor for stillbirth. Therefore antenatal detection of growth restricted babies is vital and has been shown to reduce stillbirth significantly because it gives the option to consider timely delivery of the baby at risk.

All staff looking after pregnant women must be aware however that

Small for Gestational Age (SGA) where the Estimated Fetal Weight (EFW) <10th centile  and

Fetal Growth Restriction (FGR) where a fetus fails to reach its growth potential 

are distinct entities.  Although SGA babies are at increased risk of FGR compared to appropriately grown fetuses, fetuses <3rd centile are far more likely to be FGR than fetuses between the 3rd and 10th centile. This guideline aims to identify and focus on the higher risk FGR group whilst trying to limit unnecessary intervention in the lower risk SGA group. 

Decision making relies on balancing the risks of causing mild harm to a relatively large number of infants (admission to Neonatal unit) to prevent serious harm to a small number of infants (stillbirth).

Risk assessment, surveillance and management of the FGR fetus

Risk Assessment

  1. All women should be risk assessed at booking to determine if a prescription of aspirin is appropriate. In women who have had first trimester screening carried out a further risk assessment should be carried out once the PAPP-A result is available. (Appendix 1)
  2. All women should be asked about smoking status, offered referral to smoking cessation and informed of the association between smoking , FGR and stillbirth
  3. The risk assessment pathway (Appendix 2) should be used to triage women in to those at highest risk of FGR.

Surveillance

  1. In women not undergoing serial ultrasound scan surveillance of fetal growth, assessment is performed using and plotting on the International Symphisis –Fundal height Standards Intergrowth 21st Chart.

Definitions

Definition of FGR in a previous pregnancy as a risk factor: defined as any of the following:

  1. Birthweight <3rd centile
  2. Early onset placental dysfunction necessitating delivery <34 weeks (abnormal umbilical artery Dopplers)
  3. Birthweight <10th centile with evidence of placental dysfunction as defined below for current pregnancy

Definition of FGR in a current pregnancy

  1. EFW <3rd centile
  2. EFW <10th centile with evidence of placental dysfunction (either);
    • Abnormal uterine artery Doppler between 20-24 weeks is abnormal (Mean Pulsatility Index ≥1.45)
    • Abnormal umbilical artery Doppler (Pulsatility index (PI) >95th centile, absent or reversed end diastolic flow)

Appendix 1 - NHS GG&C Guideline; Aspirin – Antenatal use of aspirin for the prevention of pre-eclampsia

Risk Level

Risk factors

Recommendation

High

  • Hypertensive disease during a previous pregnancy -Chronic kidney disease -Autoimmune disease such as  systemic lupus erthymatosus or antiphospholipid syndrome
  • Type 1 or Type 2 diabetes
  • Chronic hypertension
  • Placental histology confirming placental dysfunction in a previous pregnancy

150mg aspirin

Moderate 

  • First pregnancy
  • ≥40 years old
  • Pregnancy interval >10 years
  • Body mass index (BMI) of 35kg/m2
  • Multi-fetal pregnancy
  • Family history of preeclampsia
  • Low PAPP-A <0.4Mom (<5th centile)  

150mg aspirin ≥ 2 risk factors

Appendix 2 - Algorithm for using uterine artery Doppler as a screening tool for risk of early onset FGR (Complete BadgerNet risk assessment form)

*Abnormal Uterine Artery Doppler: Mean Pulsatility Index (PI) >95th centile. If the mean PI is <1.45 it is reported as normal. If the mean PI is ≥1.45 it is reported as abnormal.

**Other risk factors and risk assessment may necessitate shorter intervals between growth scans.

***Intergrowth charts for EFW begin at 22 weeks. AC used before then.

 

Early onset FGR is rare (0.5%). The vast majority are associated with abnormal uterine artery Doppler indices or already present EFW <10th centile in the early third trimester. Thus, uterine artery Doppler can be used in the second trimester (20-24 weeks at routine FAS) to further determine the risk of placental dysfunction and risk of hypertensive disorders and/or early onset FGR for women at high risk.

The risk factors listed here constitute those routinely assessed at booking. Other risk factors exist and risk assessment must be individualised taking into account previous medical and obstetric history and current pregnancy history. For women with maternal medical conditions and individuals with disease progression or institution of medical therapies may increase an individual’s risk and necessitate monitoring with serial scanning. For women with a previous stillbirth, management must be tailored to the previous history

Last reviewed: 21 January 2022

Next review: 01 January 2025

Author(s): Dawn Kernaghan

Approved By: Obstetrics Clinical Governance Group

Document Id: 1004