The purpose of this document is to establish detailed, quality guidelines for maternity ultrasound, as recommended by the Maternity Ultrasound Advisory Group (MUAG), to ensure that diagnostic ultrasound usage in New Zealand is clinically appropriate and uniformly of high quality.
Currently, there are local variations in both ultrasound examinations and referral pathways.
The ultrasound images documented in these guidelines are minimum images, and extended examination should be performed as appropriate.
If there is concern at any stage about fetal anomaly or wellbeing, prompt referral is required as per local referral pathways.
The following screening examinations are part of routine primary maternity health care in New Zealand and should be offered to all pregnant women.
An uncomplicated pregnancy does not generally require additional first-trimester (eg, dating) or third-trimester (eg, growth) scans.
Specific clinical indications for examinations other than the two screening scans listed above require an appropriate clinical code as per the Maternity Services Notice (the Notice) pursuant to Section 88 of the New Zealand Public Health and Disability Act 2000 (Department of Internal Affairs 2007, see Appendix 1: Ultrasound scan codes and indications).
These guidelines contain reporting recommendations, including alerts for conditions requiring urgent or semi-urgent notification to referrers.
Reporting templates are also included, but it is expected that there may be local variation in reporting pro forma.
These often complex examinations must be performed by appropriately credentialed sonographers, radiologists, sonologists, obstetric consultants with training in diagnostic ultrasound or trainees under direct supervision.
The ultrasound equipment used must be fit for purpose and appropriately maintained and serviced.
 The MUAG was a subgroup of the National Maternity Monitoring Group. For more information see the National Maternity Monitoring Group Annual Report 2017.
Pregnancy imaging without clinical indication
Any ultrasound scan that a woman is referred for should clearly note the appropriate clinical code and clinical indication.
Ultrasound scanning for the purpose of obtaining souvenir images of the fetus is not appropriate and is not funded under the Notice.
For more information, see the ISUOG statement on the non-medical use of ultrasound, 2009 (PDF, 41KB) (Abramowicz et al 2009).
The use of ultrasound should be based on rational clinical need and be underpinned by evidence-based practice. Users of ultrasound must be familiar with biological safety considerations and must implement safe practices during real-time imaging.
It is recommended that this document is not printed for clinical use, as printed versions may not reflect the most recent version available online.
The guidelines will be reviewed in 2022 or as new information becomes available.
This document refers to several guidelines produced by the New Zealand Maternal Fetal Medicine Network (NZMFMN), which is not currently active.
The NZMFMN website and guidelines may not be updated in the future, so care should be taken when viewing guidelines not directly linked by this document.
 The thermal index in soft tissue (TIS) should be used in gestations under 10 weeks of gestational age and thermal index in bone (TIB) in gestations beyond 10 weeks.
The value of the thermal index should be ≤0.7 for the majority of routine examinations. Attention to the thermal index should be paid particularly during M-mode, colour and spectral Doppler imaging as well as during transvaginal (TV) imaging.
Requires immediate transfer to an appropriate local secondary or tertiary hospital if there is immediate risk to life (in an ambulance if in the community, as appropriate).
- PV bleeding in the context of suspected accreta
- open cervix
- haemodynamically unstable woman
- sustained fetal bradycardia/tachycardia in a viable pregnancy.
Requires phone discussion with the referrer before the woman leaves the department to determine management (same-day assessment is usually required). If not available, then contact the local maternity assessment unit.
- critically abnormal Doppler, for example, umbilical artery absent or reversed end-diastolic flow
- ectopic pregnancy in a stable woman
- fetal hydrops.
Requires same-day phone discussion with the referrer.
- small for gestational age (SGA) without abnormal Doppler
- unexpected fetal anomaly or demise.
Note: Conditions and situations included in the reporting alerts boxes are not exhaustive and use of clinical judgment is required.