Small for Gestational Age and Fetal Growth Restriction in Aotearoa New Zealand: A clinical practice guideline He Aratohu Ritenga

After two and a half years of intensive work, the new national guideline on small for gestational age (SGA) and fetal growth restriction (FGR) is being published by Te Whatu Ora. A multidisciplinary panel, including College and Ngā Maia representatives, agreed research questions, reviewed the evidence, drafted recommendations and then consulted widely with maternity providers including midwives.

All College members were invited to provide feedback on the draft guideline and the College’s submission was developed from this consultation process. The College’s recommendations were incorporated into the guideline and the College’s national board endorsed the guideline after its recommended final amendments were accepted.

The SGA and FGR guideline will underpin the Aotearoa Growth Assessment Programme (GAP) education and inform the use of customised gestation-related optimal weight (GROW) charts. The new SGA and FGR definitions have also been incorporated into the Referral Guidelines (Te Whatu Ora, 2023).

The guideline is comprehensive, with 54 recommendations. To support ease of use, it is presented in two parts: a Summary of Recommendations, including the evidence level and rationale for each recommendation, and the detailed Evidence Summary. Several tables and flow charts are included for quick reference. Where relevant, responsibilities of primary (including LMC) and secondary/ tertiary maternity services are specified. A video presentation about the guideline is also being made available to support implementation. Midwives are encouraged to familiarise themselves with the new guideline.

WHY DEVELOP A NATIONAL SGA AND FGR GUIDELINE?

The aim of the guideline is to “reduce rates of stillbirth and neonatal mortality and morbidity associated with fetal growth restriction (FGR) by standardising care across Aotearoa New Zealand.” As the Evidence Summary states, “FGR affects approximately 5 to 10% of all pregnancies. FGR is associated with several adverse pregnancy outcomes, including maternal and neonatal morbidity, perinatal death and longer-term adverse health outcomes in childhood and beyond.” ACC funded the development of the guideline under its Neonatal Encephalopathy Taskforce work to support a reduction in newborn brain injury. The guideline articulates the value of screening for FGR and monitoring fetal growth and wellbeing when SGA or FGR is diagnosed. It also acknowledges the complexity of clinical judgement and recommendations inherent in this aspect of maternity care. Feedback from College members raised concern about the potential for false positive diagnoses of SGA through ultrasound, which could lead to unnecessary intervention, and this has been acknowledged in the guideline. “While antenatal identification of FGR fetuses is challenging, an approximate 60% reduction in the risk of stillbirth exists for

RECOMMENDED SCREENING SCHEDULE OF GROWTH SCANS FOR PREGNANT WOMEN/PEOPLE WITH FGR RISK FACTORS OR UNRELIABLE FUNDAL HEIGHT MEASUREMENT (TABLE 4 IN THE GUIDELINES)

Three or more minor risk factors or unreliable fundal height Major

Consider two growth scans:

• at 30 to 32 weeks’ gestation and

• at 36 to 38 weeks’ gestation

(For example, one scan at 32 weeks’ gestation and one scan at 37 weeks’ gestation) factor for SGA or FGR

Monthly growth scans starting from between 28 and 30 weeks’ gestation until birth

(For example, one scan at each of 30, 34 and 38 weeks’ gestation)

One or more risk factors for early-onset FGR

Monthly growth scans starting from between 24 and 26 weeks’ gestation until birth plus

Consider UtA Doppler study between 20 and 24 weeks’ gestation

(For example, one scan at each of 24, 28, 32, 36 and 40 weeks’ gestation)

DEFINITION FOR FGR IN THE NEONATE (TABLE 5 IN THE GUIDELINES)

• Customised birthweight <3rd centile

• Customised birthweight centile from ≥3 to <10 with two or more additional features:

- BMI z-score < -1.3

- length z-score < -1.3

- skin or body fat z-score < -1.3 (where equipment and expertise allow)

- antenatal diagnosis of FGR

- one or more major maternal risk factors for FGR

- evidence of placental insufficiency on histology pregnant women/people when FGR is recognised antenatally. Health practitioners make difficult choices when trying to balance the risks and benefits of prolonging fetal development when evidence of FGR exists, compared with preterm birth and the associated adverse outcomes. Additionally, approximately 5% of pregnancies identified antenatally as SGA are not SGA at birth. It is important to consider the implications for whānau of pathologising a normal pregnancy due to a false positive diagnosis of FGR.”

• Antenatal diagnosis of FGR and evidence of placental insufficiency (e.g., abnormal Doppler studies), even if the customised birthweight is ≥10th centile.

Wāhine Māori and Indian women have higher rates of SGA and perinatal mortality than other ethnic groups. The guideline recognises that “These risks are disproportionately experienced by Māori due to the effects of colonisation such as unequal access to resources and the social determinants of health. This highlights the need for more to be done to address the health and socioeconomic inequities affecting wāhine Māori and which underlie higher

SGA rates.” Health system-based actions to improve health equity include appropriate screening, monitoring and birth planning when SGA or FGR are present.

To support the development of balanced and contextualised recommendations for Aotearoa, the guideline panel agreed a set of guiding principles.

FIVE PRINCIPLES UNDERPIN THE CLINICAL PRACTICE RECOMMENDATIONS:

• The pregnant woman/person is at the centre of all care decisions and shares decision-making with health practitioners within Aotearoa New Zealand’s model of continuity of midwifery care.

• The optimal pregnancy outcome is the birth of a healthy, well-grown baby and a well woman/person following spontaneous onset of labour at term.

• Where a pregnancy is identified as SGA or FGR, additional monitoring and judicious use of intervention is planned with informed decision-making between the pregnant woman/person and care provider with the aim of optimising outcomes for the pregnant woman/person and baby.

• Where possible, expectant management should be planned, supporting the safe prolonging of pregnancy and physiological birth.

• Potential resource limitations and access to care and equity are considered at each step, but these considerations do not change the best practice recommendations.

The recommendations are specifically focused on SGA and FGR, which are of course situated within the midwife’s holistic care, assessment and discussions to support informed decision-making for whānau. Some of the key points for midwives include:

• As part of the midwife’s detailed health assessment at the registration appointment (and reassessed throughout pregnancy), identify if the woman/person has any risk factors for FGR (Tables 1 and 2 in the guideline). Advise women/people to stop cigarette smoking and other recreational drug use (including cannabis) before pregnancy, or by 15 weeks of pregnancy. Offer low-dose aspirin to pregnant women/people who have had a previous FGR pregnancy or who have a major risk factor for pre-eclampsia (these recommendations align with the 2022 Hypertension in Pregnancy guideline).

• Recommended screening for pregnant women/people at low risk of FGR (that is, no major and two or fewer minor risk factors) is serial fundal height assessment at each antenatal visit, plotted on a customised fundal height chart, starting at 26 to 28 weeks’ gestation. Measurements should be at least two weeks apart. If the plotted fundal height is <10th centile or if fundal height declines >30 centiles, refer for ultrasound assessment of fetal growth.

• Growth scans are recommended in the third trimester for women and people with risk factors as per the table on previous page. Plot EFW on a customised GROW chart.

• If SGA (EFW or AC <10th customised centile) or FGR (definition in Table 1 of the guideline) is diagnosed, recommend referral to an obstetrician for monitoring and birth planning.

• Additional monitoring is recommended for neonates with FGR, with paediatric review in some circumstances.

• Midwives have a role in assessing newborns for FGR. Babies with a birthweight <3rd customised centile have FGR. For babies where FGR is suspected (e.g. birthweight 3rd to <10th customised centile or a decline in EFW >30 centiles during pregnancy), the midwife enters routinely taken measurements into an easy-to-use calculator which calculates BMI and provides ‘z-scores’ for BMI, weight and length. This enables midwives to diagnose FGR according to Table 5 in the guideline. Babies who are confirmed as SGA but not FGR do not need the same level of monitoring or investigations.

Access To Ultrasound

It is anticipated that the ultrasound recommendations will provide clarity on who should be offered third trimester ultrasound and who should not; for example, recommendation 14 states, “Do not offer routine ultrasound for fetal growth assessment to pregnant women/ people without ≥1 major or ≥3 minor risk factors for FGR.” The College has consistently raised concerns about access to pregnancy ultrasound with ACC and Te Whatu Ora to ensure this guideline is equitably implemented. Te Whatu Ora has issued the following statement:

“Te Whatu Ora acknowledges that there are barriers to accessing ultrasound scanning and anticipates that fully embedding this guideline may take some time. We are actively working towards solutions to improve access. It is expected that practitioners utilise this guideline to the best of their ability, ensuring clear documentation and rationale when there is an inability to do so”. square

References available on request.