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Antepartum haemorrhage and abnormal placentation

#Background

The term antepartum haemorrhage describes any bleeding from the genital tract after 20 weeks gestation. It is commonly estimated to impact 3-5% of pregnancies. There are many causes of antepartum haemorrhage, the most common causes for significant and/or ongoing bleeding are placental edge bleeds, placental abruption, placenta praevia, placenta accreta spectrum (PAS) disorder, uterine rupture and vasa praevia. Other causes include bleeding from the cervix, vagina and vulva (e.g. infection, malignancy, polyp and trauma).

For the majority of wāhine/people presenting with antepartum haemorrhage at <37+0 weeks, an approach of expectant management is most appropriate and should be planned to gain maturity for pēpi. However, bleeding may be significant and provider initiated preterm birth may be indicated due to compromise to māmā/person and/or pēpi wellbeing. Significant antepartum haemorrhage is also a recognised risk factor for later development of fetal growth restriction (FGR) and later spontaneous preterm prelabour rupture of membranes (PPROM) and preterm labour.

This section of Taonga Tuku Iho focuses on aspects of pregnancy care and antepartum haemorrhage pertinent to preterm birth and limiting the impact of this for māmā/person and pēpi. It considers general antepartum haemorrhage, abruption and placenta praevia together. PAS and vasa praevia are considered separately.

#Recommendations and Practice

Guideline Recommendations (pink boxes) and Good Practice (yellow boxes) are provided as recommendations of practice. Comprehensive clinical oversight of māmā/person and pēpi wellbeing is required, and this may influence how these recommendations of practice are used.

Each recommendation of practice should be considered in consultation with wāhine/people and whanāu, including clear explanations to allow informed decision-making. Wāhine/people have the right to decline a recommendation of practice. In these circumstances, healthcare providers should follow their professional responsibilities for ongoing care. 15-18

Antepartum haemorrhage, placental abruption and placenta praevia

Antepartum haemorrhage describes any bleeding from the genital tract after 20 weeks gestation. A placental abruption describes a placenta that partly or completely separates away from the uterine wall before birth. Placenta praevia describes a placenta that is partly or completely within the lower segment of the uterus. The Manatū Hauora New Zealand Obstetric Ultrasound Guidelines4 use the following terms to describe types of placenta praevia:

  • Complete placenta praevia: Placenta completely covers the internal cervical os
  • Partial placenta praevia: Placenta is partly over the cervix
  • Marginal praevia: Placenta is near the edge of the cervix
  • Low-lying placenta: Placenta/marginal sinus is 20 mm or less from the internal cervical os.

For the majority of wāhine/people presenting with antepartum haemorrhage at <37+0 weeks, an approach of expectant management is most appropriate and should be planned to gain maturity for pēpi. This section of Taonga Tuku Iho focuses on aspects of pregnancy care and antepartum haemorrhage pertinent to preterm birth and limiting the impact of this for māmā/person and pēpi.

Guideline Recommendations
— Antepartum haemorrhage, placental abruption and placenta praevia diagnosis, antenatal management and timing of birth

  • The placental location should be assessed and documented at the time of the second-trimester anatomy scan (19+ weeks).4
  • A transvaginal scan should be considered and offered if the placenta is not well visualised on transabdominal scan.4
  • When the placental edge is <20mm from the internal cervical os, a third trimester follow-up scan (usually at 32 weeks) should be offered and arranged.4
  • Where there is suspicion of PAS, a referral for specialist review should be recommended and made promptly and preferably by 24 weeks gestation.
  • In case of velamentous cord insertion, placenta praevia or succenturiate lobe, careful assessment of the internal os is required with colour Doppler, with a low threshold to consider transvaginal imaging, to identify or exclude vasa praevia.4

  • For wāhine/people presenting with antepartum haemorrhage, ongoing care including plans for birth will be dependent on several factors including the amount and presumed cause of bleeding, gestation and evidence of māmā/person and/or pēpi wellbeing.

  • For wāhine/people presenting with antepartum haemorrhage at <37+0 weeks, a general approach of expectant management should be planned.

  • Indications to consider preterm birth with antepartum haemorrhage include:

    - Where there is potentially significant compromise to māmā/person and/or pēpi wellbeing that cannot be reversed with initial resuscitative efforts, regardless of cause or gestation.

    - Where there is suspected/confirmed PAS and ≥34+0 weeks.

    - Where there is placenta praevia and ≥36+0 weeks.

    - Where there is known vasa praevia.

  • If significant bleeding occurs, appropriate and timely preparation to optimise outcomes for pēpi should be made when preterm birth is planned or considered likely.
  • In utero transfer should be considered for wāhine/people who are in a unit without the appropriate level of neonatal care.
  • Antenatal corticosteroids should be administered when gestational age is ≤34+6 weeks and birth is planned or anticipated within the next seven days, even if birth is likely within 24 hours.
  • Repeat corticosteroid doses/courses should be administered when gestational age is ≤32+6 weeks, if 7-14 days since previous corticosteroid and preterm birth is anticipated or planned within the next seven days, even if birth is likely within the next 24 hours, to a maximum of three single weekly repeat doses OR one repeat course of two doses.
  • Magnesium sulphate should be administered when gestational age is <30+0 weeks and birth is planned and is ideally given for at least four hours prior to birth.
  • Birth should not be delayed to allow time for in utero transfer, corticosteroid and/or magnesium sulphate administration if the delay would be detrimental to the immediate wellbeing of the wāhine/person and/or pēpi.
  • For wāhine/people with placenta praevia and recurrent antepartum haemorrhage, in-patient admission in a unit with the appropriate level of neonatal care should be planned and continue until the time of birth.
  • Significant antepartum haemorrhage is a recognised major risk factor for FGR later in pregnancy.
  • Recommend and arrange a monthly ultrasound scan for fetal growth assessment from the time of antepartum haemorrhage until birth.19
  • If FGR occurs, follow the adapted Te Whatu Ora SGA and FGR In Aotearoa New Zealand clinical practice guideline for fetal surveillance and management.19

Good Practice
— Antepartum haemorrhage, placental abruption and placenta praevia diagnosis, antenatal management and timing of birth

  • Following an antepartum haemorrhage wāhine/people should be advised on the increased chance of subsequent PPROM and preterm labour. This should include verbal and written information on the signs and symptoms of preterm labour and actions to take in event of these. These tools should allow for different levels of health literacy, ethnic and cultural backgrounds, and a variety of preferred first languages.
  • Interpreter services and cultural support should be available and offered to all wāhine/people and whānau to support the provision of information.

The Carosika Whānau Information on antepartum haemorrhage (APH) & preterm birth may be used to support conversations with wāhine/people and whānau.

Published: June 2025 | PDF

Download - The Carosika Whānau Information on antepartum haemorrhage (APH) & preterm birth may be used to support conversations with wāhine/people and whānau.

Placenta accreta spectrum disorder

Placenta accreta spectrum (PAS) disorder, also known as abnormally invasive placenta (AIP), occurs when the placenta infiltrates into, and sometimes beyond, the myometrium of the uterus. This results in the placenta being abnormally adherent to the uterus. It does not easily separate away from the uterus after birth and may result in major and life-threatening haemorrhage.

Standard terminology for PAS considers three main subtypes:12,20

  • Placenta accreta: densely adherent placenta due to abnormally deep invasion of the placenta onto the myometrium (possibility placenta will separate at birth).
  • Placenta increta: adherent placenta embedded into the myometrium (placenta unlikely to separate at birth).
  • Placenta percreta: adherent placenta growing through the uterus and with possible involvement of other organs (placenta unlikely to separate at birth).

PAS is a rare but serious condition that is most commonly associated with previous caesarean section (or other uterine scarring). With rising caesarean section rates worldwide, there are rising rates of PAS. Most recently reported incidence of PAS is approximately 2 per 1000 for those wāhine/people with previous caesarean section birth.20

For most wāhine/people with PAS, although pregnancies may be complicated and require specialist care including transfer of care to other regions, the chance of early (<32 weeks) preterm birth remains relatively low. There is a significant chance of late preterm birth (34+0 to 36+6 weeks). This section of Taonga Tuku Iho focuses on aspects of pregnancy care and PAS pertinent to preterm birth and limiting the impact of this for māmā/person and pēpi.

Guideline Recommendations
— Placenta accreta spectrum disorder diagnosis, antenatal management and timing of birth

  • Ultrasound should be the first line imaging modality for the diagnosis of PAS. Where PAS is suspected, a specialist with appropriate skills should make the diagnosis using standardised definitions for reporting.12
  • MRI imaging may be a useful adjunct to ultrasound imaging for diagnosis and evaluation.12
  • For wāhine/people with probable or confirmed PAS, care should be supported and provided by a specialised PAS multidisciplinary team in a centre with appropriate facilities.
  • A specialised PAS multidisciplinary team should include: specialist obstetrician, specialist anaesthetist, imaging expert, surgeons with skills in complex surgery (often a gynaecology oncologist, urologist and vascular surgeon), interventional radiologist and neonatologist.1,12
  • Facilities and expertise on-site where care and birth are planned for PAS should include: on-site transfusion service/major haemorrhage protocols/haematological expertise/blood salvage facilities, adult intensive care, neonatal intensive care, rapid access to vascular and colorectal surgeons and interventional radiology.1,12
  • Referral to a specialised multidisciplinary team should be recommended and made shortly after first diagnosis or when there is a high suspicion of PAS.12
  • In-patient management is not recommended routinely for wāhine/people with PAS who are asymptomatic.1 However, adequate resources should be available to support rapid attendance if symptoms develop.1
  • A PAS bundle checklist or template should be utilised to summarise and record a care plan. An example can be accessed here.
  • Timing of birth should be individualised based on the clinical scenario, balancing risks of haemorrhage and emergency birth with the need to optimise pēpi maturity.12
  • For wāhine/people who remain asymptomatic (no bleeding, no PPROM and no regular uterine contractions) and have no prior preterm birth, expectant management to 36+0 weeks should be considered.1
  • For wāhine/people with a prior preterm birth, multiple episodes of small bleeding or a single significant bleed or PPROM, birth at around 34+0 weeks should be considered.1
  • If significant bleeding occurs, appropriate and timely preparation to optimise outcomes for pēpi should be made when preterm birth is planned or considered likely.
  • In utero transfer should be considered for wāhine/people who are in a unit without the appropriate specialised PAS multidisciplinary team and facilities and appropriate level of neonatal care.
  • Antenatal corticosteroids should be administered when gestational age is ≤34+6 weeks and birth is planned or anticipated within the next seven days, even if birth is likely within 24 hours.
  • Repeat corticosteroid doses should be administered when gestational age is ≤32+6 weeks, if 7-14 days since previous corticosteroid and preterm birth is anticipated or planned within the next seven days, even if birth is likely within the next 24 hours, to a maximum of three single weekly repeat doses OR one repeat course of two doses.
  • Magnesium sulphate should be administered when gestational age is <30+0 weeks and birth is planned for PAS and is ideally given for at least four hours prior to birth.
  • Birth should not be delayed to allow time for in utero transfer, corticosteroid and/or magnesium sulphate administration if the delay would be detrimental to the immediate wellbeing of the wāhine/person and/or pēpi.
  • If preterm birth is planned for PAS at 34+0 to 34+6 weeks and no prior antenatal corticosteroids have been administered, a first course of corticosteroids should be offered and given between 48 hours and seven days prior to planned birth.
  • If preterm birth is planned for PAS at 35+0 to 36+6 weeks and no prior antenatal corticosteroids have been administered, the balance of benefit and potential harm should be considered by clinicians and discussed with wāhine/people and their whānau. Whilst equipoise on benefit/risk profile remains, the use of corticosteroids should be as an exception rather than as the standard of care.
  • In units participating in the C*STEROID and PRECeDe trials (corticosteroids prior to planned caesarean section birth wāhine/people without and with diabetes in pregnancy respectively), participation should be offered prior to planned caesarean section at 35+0 to 36+6 weeks when no prior antenatal corticosteroids have been administered.

Good Practice
— Placenta accreta spectrum disorder diagnosis, antenatal management and timing of birth

  • Wāhine/people and whānau may need timely relocation and transfer of care prior to, and for birth to receive care by a specialised PAS multidisciplinary team in a centre with appropriate facilities (likely to be nearest tertiary unit).
  • Each unit should provide clear instruction on local processes for referral and transfer.
  • Travel and accommodation support must be provided to wāhine/people and their whānau.
  • Travel and accommodation should be arranged through the National Travel Assistance (NTA) scheme.
  • Each referring unit must have clear and easily accessible systems and processes to enable whānau travelling away from home to support wāhine/people.
  • Wherever possible, costs should be met directly by the referring unit without expectation of ‘upfront’ payments (with reimbursement) for whānau.
  • Appropriate cultural and whānau support should be offered to wāhine/people and whānau who are being cared for distant from home and own support networks.
  • Wāhine/people should be provided with verbal and written information on relocation and transfer of clinical responsibility. These tools should allow for different levels of health literacy, ethnic and cultural backgrounds, and a variety of preferred first languages.
  • Interpreter services and cultural support should be available and offered to all wāhine/people and whānau to support the provision of information.

Vasa praevia

Vasa praevia occurs when exposed fetal vessels within the amniotic membranes cover, or are within 20 mm of, the internal cervical os. The Manatū Hauora New Zealand Obstetric Ultrasound Guidelines4 describe two types of vasa praevia:

  • Type 1: with velamentous insertion of the umbilical cord into the placenta.
  • Type 2: with velamentous fetal vessels connecting the placenta to a succenturiate placental lobe.

Vasa praevia is a rare but serious condition occurring in approximately 1 in 1200 pregnancies. 21 If the exposed fetal vessels rupture at the time of spontaneous or artificial rupture of membranes, exsanguination and pēpi death is rapid. Vasa praevia is associated with a high mortality rate for pēpi if not diagnosed in the antenatal period with planned early birth. This high mortality rate at term provides clear justification for provider initiated preterm birth. Due to the rare nature of this condition and the severe nature of the outcome, clinical trials are unlikely to be undertaken. Current recommendations for care are based on retrospective case series with consensus and expert opinion.

This section of Taonga Tuku Iho focuses on aspects of pregnancy care and vasa praevia pertinent to preterm birth and limiting the impact of this for māmā/person and pēpi.

Guideline Recommendations
— Vasa praevia diagnosis, antenatal management and timing of birth

  • Placental localisation and the position of the cord insertion should be documented at the time of the second-trimester anatomy scan (19+ weeks).
  • In cases of velamentous cord insertion, placenta praevia or succenturiate lobe, careful assessment of the internal os is required with colour and pulsed wave Doppler, with a low threshold to consider transvaginal imaging, to identify vasa praevia.4
  • Vasa praevia should be diagnosed when a fetal vessel, or vessels, are seen traversing across the internal cervical os or within 20 mm.
  • For wāhine/people with known vasa praevia, discussion and planning for admission to hospital with appropriate level of neonatal care should be considered from 30+0 weeks.
  • An alternative of outpatient care may be considered with evidence of a long, closed cervix (>25mm) in serial transvaginal ultrasound scans and with no other clinical concerns.
  • Planned early birth at 34+0 to 36+0 weeks should be considered.
  • There is no benefit from planning expectant management ≥37+0 weeks.
  • Administration of antenatal corticosteroids should be considered from 30+0 weeks, in preparation for immediate caesarean birth in event of PPROM, bleeding or active labour.
  • Administration of repeat corticosteroid doses/courses should be considered once first course has been given if 7-14 days since previous corticosteroid and up to ≤32+6 weeks, to a maximum of three single weekly repeat doses OR one repeat course of two doses.
  • If corticosteroids have not been given in anticipation of possible emergency birth, and birth is planned ≤34+6 weeks, a first course of corticosteroids should be recommended and given between 48 hours and seven days prior to planned birth.
  • If corticosteroids have not been given in anticipation of possible emergency birth, and birth is planned birth is at 35+0 to 36+6 weeks, the balance of benefit and potential harm should be considered by clinicians and discussed with wāhine/people and their whānau. Whilst equipoise on benefit/risk profile remains, the use of corticosteroids should be as an exception rather than as the standard of care.
  • In units participating in the C*STEROID and PRECeDe trials (corticosteroids prior to planned caesarean section birth wāhine/people without and with diabetes in pregnancy respectively), participation should be offered prior to planned caesarean section at 35+0 to 36+6 weeks when no prior antenatal corticosteroids have been administered.
  • In the event of bleeding and a suspected vasa praevia, birth by category 1 caesarean section should be undertaken with support for neonatal resuscitation including access for immediate transfusion with O Rhesus negative blood. Those responsible for neonatal care should be advised of suspected pēpi blood loss prior to caesarean section.

Good Practice
— Vasa praevia diagnosis, antenatal management and timing of birth

  • For wāhine/people being managed with in-patient care from ≥30+0 weeks, plans should be in place to enable category 1 caesarean section (e.g. current ‘group and hold’ blood sample available in laboratory, completed written consent).
  • At the time of caesarean section for vasa praevia, immediate cord clamping should be performed (not deferred) in case fetal vessels have ruptured at the time of membrane rupture and to avoid further blood loss for pēpi.
  • Wāhine/people and whānau may need timely relocation and transfer of care prior to, and for birth to receive care in a unit with appropriate neonatal care.
  • Each unit should provide clear instruction on local processes for referral and transfer.
  • Travel and accommodation support must be provided to wāhine/people and their whānau.
  • Travel and accommodation should be arranged through the National Travel Assistance (NTA) scheme.
  • Each referring unit must have clear and easily accessible systems and processes to enable whānau travelling away from home to support wāhine/people.
  • Wherever possible, costs should be met directly by the referring unit without expectation of ‘upfront’ payments (with reimbursement) for whānau.
  • Appropriate cultural and whānau support should be offered to wāhine/people and whānau who are being cared for distant from home and own support networks.
  • Wāhine/people should be provided with verbal and written information on relocation and transfer of care. These tools should allow for different levels of health literacy, ethnic and cultural backgrounds, and a variety of preferred first languages.
  • Interpreter services and cultural support should be available and offered to all wāhine/people and whānau to support the provision of information.

#Auditable Standards

To be developed.

 

#Included guidelines

The search identified 11 guidelines that met criteria for high-quality and/or were recommended for use or use with modifications by the Review Panel.1-11 One guideline was assessed to be high-quality in Rigour of Development (score >60%) and Overall Assessment (score >60%) and recommended for use.1 Three guidelines were assessed to be high-quality in Overall Assessment (score >60%), but not in Rigour of Development (score >60).2,4,5 The remaining seven guidelines were recommended for use with or without modifications.3,6-11

One guideline was national,4 three guidelines were international/bi-national (Aotearoa and Australia),1-3 and seven were district-specific.5-11 Four guidelines were specific to the management of PAS,1,3,5,9 two were specific to antepartum haemorrhage,6,10 one was specific to vasa praevia,2 three included antepartum haemorrhage and PAS7,8,11 and one was specific to ultrasound imaging.4 Since the search was undertaken the Royal Australian and New Zealand College of Obstetricians and Gynaecologists (RANZCOG) PAS guideline has been updated; the newer 2023 version12 has been used.

Recommendations on antepartum haemorrhage and placenta praevia have been made using the Manatū Hauora New Zealand Obstetric Ultrasound Guidelines4 and with reference to the district guidelines on antepartum haemorrhage that were identified by the Review Panel as suitable for use with or without modification (no guidelines specific to antepartum haemorrhage and placenta praevia were appraised as high-quality).

Recommendations on PAS have been based on the RANZCOG PAS Guideline12 and the International Society for Abnormally Invasive Placenta (IS-AIP) Evidence-based guidelines for the management of abnormally invasive placenta.1 The RANZCOG PAS guideline was developed by the RANZCOG PAS Guideline Development Group using identified local and international guidelines and a literature search. It was approved by the RANZCOG Women’s Health Committee and associated working groups, RANZCOG Council and Board. IS-AIP is an international group of expert clinicians and scientists. The IS-AIP guidelines were developed through a Delphi survey to identify the research questions, a systematic review, consensus meeting and membership ratification.

Recommendations on vasa praevia have been based on RANZCOG Vasa Previa Statement 2019.2 This guideline is reported as ‘under review’ (February 2025).

#Impact on equity

The vision of the Carosika Collaborative is ‘Equity in preterm birth outcomes will be achieved in Aotearoa by lowering preterm birth rates and optimising preterm birth care' ; Taonga Tuku Iho is a major tool to support this. Equity has been prioritised throughout the development process of Taonga Tuku Iho and will drive its implementation and measurement of impact.

During the identification, evaluation and selection of the clinical practice guidelines that inform Taonga Tuku Iho, the Review Panel considered the potential impact on equity of recommendations within each guideline13 and these are summarised here.

Within Aotearoa, rates of antepartum haemorrhage, placenta praevia, vasa praevia and PAS are not reported at a population level, making it difficult to determine if differences exist by factors such as ethnicity, region of residence and socioeconomic status. Te Whatu Ora maternity clinical indicators that reflect more severe bleeding include indicator 14 ‘women having a peripartum hysterectomy’ and indicators11 and 12 regarding rates of blood transfusion with caesarean section and vaginal birth respectively.14 As these indicators will include other contributing factors and with overall low event rates, analysis by equity factors adds little value.

Review Panel guideline assessments identified that the recommendations in seven of the 10 guidelines meeting criteria for consideration of inclusion in this guide had potential to increase differences by equity factors.1,2,5,7,8,10,11

A major constraint to providing consistent care for PAS is the need for a large multidisciplinary team with specialist support services such as interventional radiology, which can only be provided effectively within tertiary settings. Several reviewers highlighted this, noting the need for planned transfer for care with wāhine/people and whānau potentially spending long periods of time away from home, extended whānau and work. Hence, the impact is most profound for rural whānau and those whose local hospital is non-tertiary. A lack of consideration of different cultural approaches to support psychosocial factors when regional transfer for care is recommended was noted and of importance for whānau Māori. Alternatively, when emergency care needs to be provided without transfer for care, this may be in units with less resource and with care provided by clinicians with less knowledge, experience and skill.

For some regions a lack of capacity and capability in ultrasound services and, in particular, for more specialist experience in placental imaging including access to MRI when PAS or vasa praevia may be suspected may lead to greater differences in outcomes between regions.

#Current research

None identified.

#Statement on rationale for any differing recommendations from the high-quality guidelines

It is noted that at the time of preparing this section the RANZCOG Vasa Previa Statement 20192 is reported as ‘under review’ (February 2025) and hence recommendations may change.

We have provided some additional recommendations regarding relocation and transfer of care; these are not included in the RANZCOG guideline but may help to support equity of access to the appropriate level of care for wāhine/people with vasa praevia and their whānau in Aotearoa. A recommendation on cord clamping practice after birth is also included and in keeping with recommendations made in the Taonga Tuku Iho Preparing for Preterm Birth section.

#References

1. Collins SL, Alemdar B, van Beekhuizen HJ, Bertholdt C, Braun T, Calda P et al. Evidence-based guidelines for the management of abnormally invasive placenta: recommendations from the International Society for Abnormally Invasive Placenta. Am J Obstet Gynecol. 2019;220(6):511-26. DOI: 10.1016/j.ajog.2019.02.054.

2. The Royal Australian and New Zealand College of Obstetricians and Gynaecologists. Vasa praevia. 2019. Available from: https://ranzcog.edu.au/wp-content/uploads/2022/05/Vasa-Praevia.pdf.

3. The Royal Australian and New Zealand College of Obstetricians and Gynaecologists. Placenta Accreta. 2015. Available from: https://ranzcog.edu.au/wp-content/uploads/2022/05/Placenta-Accreta.pdf.

4. Ministry of Health. New Zealand Obstetric Ultrasound Guidelines. 2019. Available from: https://www.tewhatuora.govt.nz/publications/new-zealand-obstetric-ultrasound-guidelines.

5. Waikato District Health Board. Management of Suspected Placenta Accreta, Percreta or Increta. Hamilton: Waikato District Health Board; 2020.

6. Waikato District Health Board. Ante-partum Haemorrhage. Hamilton: Waikato District Health Board; 2019.

7. Auckland District Health Board. Antepartum haemorrhage. Auckland: Auckland District Health Board; 2015.

8. Canterbury District Health Board. Antepartum haemorrhage (excluding placenta praevia). Christchurch: Canterbury District Health Board; 2019.

9. Counties Manukau District Health Board. Guideline: Placenta praevia and placenta accreta. Auckland: Counties Manukau District Health Board; 2020.

10. Northland District Health Board. Antepartum haemorrhage. Whangarei: Northland District Health Board; 2017.

11. Nelson Marlborough District Health Board. Ante-partum and Intra-partum Haemorrhage. Nelson: Nelson Marlborough District Health Board; 2021.

12. The Royal Australian and New Zealand College of Obstetricians and Gynaecologists. Placenta Accreta Spectrum (PAS). 2023. Available from: https://ranzcog.edu.au/wp-content/uploads/Placenta-Accreta-Spectrum.pdf.

13. Hunter B, Dawes L, Wadsworth M, Sadler L, Edmonds L, McAra-Couper J, Allen-Mokaraka T, Groom KM. An evaluation of the quality, suitability and impact on equity of clinical practice guidelines relevant to preterm birth for use in Aotearoa New Zealand. BMC Pregnancy Childbirth. 2024;24(1):234. DOI: 10.1186/s12884-024-06415-0.

14. Te Whatu Ora Health New Zealand. Maternity clinical indicator trends: Te Whatu Ora Health New Zealand; 2024. Available from: https://tewhatuora.shinyapps.io/maternity-clinical-indicator-trends/.

15. New Zealand College of Midwives. Consensus Statement: Informed Consent and Decision Making. 2016. Available from: https://www.midwife.org.nz/wp-content/uploads/2019/05/Informed-Consent-and-Decision-Making.pdf.

16. Medical Council of New Zealand. Good Medical Practice. 2021. Available from: https://www.mcnz.org.nz/assets/standards/b3ad8bfba4/Good-Medical-Practice.pdf.

17. The Royal Australian and New Zealand College of Obstetricians and Gynaecologists. Consent and provision of information to patients in New Zealand regarding proposed treatment. 2019. Available from: https://ranzcog.edu.au/wp-content/uploads/Consent-Provision-Information-to-Patients-New-Zealand.pdf.

18. Te Whatu Ora - Health New Zealand. Guidelines for Consultation with Obstetric and Related Medical Services (Referral Guidelines) 2023. Available from: https://www.tewhatuora.govt.nz/publications/guidelines-for-consultation-with-obstetric-and-related-medical-services-referral-guidelines/.

19. Te Whatu Ora - Health New Zealand. Small for Gestational Age and Fetal Growth Restriction in Aotearoa New Zealand He Aratohu Ritenga Haumanu mō te Tōhuatanga Kōpiri me te Pakupaku Rawa. A clinical practice guideline 2023. Available from: https://www.tewhatuora.govt.nz/publications/small-for-gestational-age-fetal-growth-restriction-guidelines/.

20. Jauniaux E, Ayres-de-Campos D. FIGO consensus guidelines on placenta accreta spectrum disorders: Introduction. Int J Gynaecol Obstet. 2018;140(3):261-4. DOI: 10.1002/ijgo.12406.

21. Zhang W, Giacchino T, Chanyarungrojn PA, Ionescu O, Akolekar R. Incidence of vasa praevia: a systematic review and meta-analysis. BMJ Open. 2023;13(9):e075245. DOI: 10.1136/bmjopen-2023-075245.

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