Mode of preterm birth

#Background

There is insufficient high-level evidence to guide practice on mode of birth (planned vaginal or caesarean section birth) for wāhine/people facing anticipated or planned preterm birth. As with term birth, there are some clear indications when planned caesarean section birth has advantage over planned vaginal birth for māmā/person and/or pēpi. There are also additional relative indications and some specific to preterm birth that favour planned caesarean section birth. However, there are also risks associated with planned caesarean section that are specific for preterm birth. These should be considered and included when making assessments and counselling wāhine/people and whānau on the balance of benefits and risks for each mode of birth. Mode of birth decisions should be individualised in the context, gestation and individual risk profile of each wahine/person.

For preterm pēpi, requiring planned early birth for māmā/person and/or pēpi health, caesarean section may be, but is not always, indicated due to concerns about time taken for vaginal birth and/or wellbeing of māmā/person and/or pēpi during labour. It is also possible that planned caesarean section birth involves a less physically traumatic birth for some pēpi and so may be considered for spontaneous preterm labour. This has not been substantiated in randomised trials¹ but may explain differences seen in observational studies of those more fragile extreme preterm and very low birthweight pēpi.^2,3 Counter to this, planned caesarean section prior to the onset of labour is associated with a higher risk of neonatal respiratory morbidity than planned vaginal birth at term gestations,⁴ and so may potentially exacerbate a common complication of prematurity. Furthermore, and specific to spontaneous preterm birth, it is possible that proceeding with a planned caesarean section may increase the number of preterm births and earlier gestations at birth, as the signs and symptoms of preterm labour often settle and wāhine/people subsequently give birth at later gestations including at term.⁵

At later preterm gestations the risks of complications from a caesarean section or vaginal birth are similar to those at term. At very early gestations, caesarean section birth may pose additional risk for wāhine/people. With decreasing gestation and in particular at <28 weeks,the lower uterine segment is less likely to be well formed and the chance of requiring a classical (vertical) or high transverse uterine incision is higher. This may bring additional risk of morbidity intraoperatively and for future pregnancies.^6,7

For wāhine/people having a planned vaginal preterm birth, there may be indications where assistance in birth is required in the second stage. There is very limited randomised evidence to guide practice on choice of instrument where this is necessary but observational data and safety concerns with vacuum extraction favour use of forceps when required for early preterm birth.⁸

#Recommendations and Practice

There are several factors that influence mode of birth at preterm gestations, including the indication for birth, fetal presentation, gestational age, and whether it is a multiple pregnancy.

Mode of birth according to indication for preterm birth

Recommendations for planned mode of birth for wāhine/people who are at high risk of, or are already established in, spontaneous preterm labour may differ to those who have a provider-initiated indication for preterm birth and require either induction of labour or prelabour caesarean section. Decisions about the latter should consider māmā/person and pēpi wellbeing, the likelihood of success of induction of labour and expected time taken to achieve birth.

There is very limited randomised evidence to inform mode of birth for wāhine/people in spontaneous preterm labour, but guidance is included in the 2015 World Health Organization (WHO) recommendations on interventions to improve preterm birth outcomes.⁹ This guidance is based on the findings of the 2013 Cochrane review of planned caesarean section and planned vaginal birth for spontaneous preterm labour.¹ Only four studies with 116 wāhine/people were included with all trials stopping early due to poor recruitment. These limited data show no difference for pēpi in terms of birth injury, birth asphyxia or survival but planned caesarean section was associated with an increased risk of major maternal postpartum complications (RR 7.21, 95% CI 1.37-38.08).¹

Spontaneous Preterm Labour

Mode of birth for non-cephalic presentation

There is limited randomised evidence to guide recommendations on mode of birth for breech presentation at preterm gestations. Most evidence is limited to observational data and focussed on extreme preterm birth (<28 weeks).

Concerns exist about the risk of harm due to head entrapment and other trauma in extreme preterm breech birth. A 2017 systematic review of mostly observational data, assessed survival and brain injury by mode of birth for actively resuscitated breech singletons born at 23⁺⁰ to 27⁺⁶ weeks gestation (15 studies, 12,335 infants).² Caesarean section was associated with a 41% reduction in death up to 6 months of age (OR 0.59, 95% CI 0.36-0.95), however, this benefit was only significant at 23⁺⁰ to 24⁺⁶ weeks (OR 0.58, 95% CI 0.44-0.75) and there was no benefit at 27⁺⁰ to 27⁺⁶ weeks (OR 2.04, 95% CI 0.2-20.6).² A similar effect by gestational age was seen for intraventricular haemorrhage (overall OR 0.51, 95% CI 0.29-0.91, non-significant at 27⁺⁰ to 27⁺⁶ weeks OR 0.91, 95% CI 0.27-3.05).²

These observational data should be interpreted with caution due to the inability to fully control and adjust for other contributing factors but should be included in overall consideration of the benefits and risks of vaginal birth and caesarean section. There is no evidence to support extrapolating the findings of these data to later preterm gestational ages.

Mode of birth at extreme preterm gestation (23⁺⁰ to 24⁺⁶ weeks)

As noted above, non-randomised evidence suggests there may be some benefit of considering a caesarean section birth for breech presentation at <27⁺⁰ weeks. Consideration has also been given to possible benefit of caesarean section for extreme preterm cephalic presentation births. A 2020 systematic review of observational studies assessed outcomes for cephalic singleton pēpi born <28 weeks or <1500g (14 studies, 129,475 infants).³ For births <28 weeks, caesarean section was associated with a 48% reduction in mortality (aOR 0.62, 95% CI 0.39-0.99) but with far fewer studies and participants included in analysis (three, 10,331 respectively).³ Of note, for pēpi with a very low birth weight <1500 grams (two studies, 105,439 pēpi) there was no significant reduction in death (aOR 0.77, 95% CI 0.55-1.07), although benefits were associated with caesarean section for lower birthweights, 500-700 grams (aOR 0.53, 95% CI 0.49-0.57, one study, 5989 pēpi) and 1000-1250g (aOR 0.78, 95% CI 0.65-0.93, one study, 14,906 pēpi).³

These observational data should be interpreted with considerable caution due to the inability to fully control and adjust for other contributing factors. Several additional factors should be considered when planning preferred mode of birth including whether wāhine are in/or are likely to establish in spontaneous labour, or whether birth is provider-initiated due to compromise to māmā/person and/or pēpi Furthermore, the risks for wāhine/people undergoing a caesarean section at extreme preterm gestations are higher, including classical (vertical) or high transverse uterine incision³ which is associated with increased intraoperative blood loss^2,6 and recommendation for repeat caesarean section in all future pregnancies due to the risk of uterine rupture.⁷ These risks need to be balanced against potential for improved outcomes for pēpi.

Mode of birth for wāhine/people with multiple pregnancy

Wāhine/people with multiple pregnancy are at an increased risk of spontaneous and all types of provider-initiated preterm birth. In considering mode of birth, recommendations by indication for preterm birth should be considered.

For otherwise uncomplicated twin births, the Twin Birth Study provides evidence to inform practice.⁴² This randomised trial, included 2804 wāhine/people with twin pregnancies and leading twin in cephalic presentation from 32⁺⁰ weeks, 47% birthed <37 weeks.⁴² The rate of fetal/neonatal death or serious neonatal morbidity was the same for those neonates born by planned caesarean birth or planned vaginal birth (2.2% and 1.9%, OR 1.16, 95% CI 0.77-1.74).⁴² Planned mode of birth also had no impact on death or neurodevelopment by two years of age.⁴³

Of particular note, secondary analysis by gestation at birth demonstrates differences by gestational age at birth, with an increase in the composite adverse perinatal outcome with planned vaginal birth after 37 weeks, but a trend towards a decrease in adverse outcome with planned vaginal birth at 32⁺⁰-36⁺⁶ weeks, 2.2% and 3.6%, OR 0.62, 95% CI 0.37–1.03. Secondary analysis including only monochorionic diamniotic (MCDA) twin pregnancies, of which 85% birthed before 37⁺⁰ weeks, also showed no benefit of planned caesarean section.⁴⁴

Use of instrumental birth at preterm gestations

There is limited randomised evidence comparing the safety and effectiveness of forceps and ventouse (soft or rigid cups) to achieve vaginal birth at preterm gestations. In the 2021 Cochrane review of ‘Instruments for assisted vaginal birth’, four of 30 studies included wāhine/people at gestational ages between 34 and 36⁺⁶ weeks, the remainder included only term pregnancies.⁴⁵ No subgroup analysis of preterm births was undertaken. A major reason for the lack of inclusion of preterm gestations, is the concern for fetal trauma associated with the vacuum required for effective ventouse birth including an increased risk of subgaleal haemorrhage, other cerebral bleeding and scalp trauma.^8,46

The Royal Australian and New Zealand College of Obstetricians and Gynaecologists evidence statement on ‘Instrumental vaginal birth’ recommends that ventouse should not be used at <34 weeks gestation and that due to uncertainty in safety it should be used with caution at 34⁺⁰ to 36⁺⁰ weeks.⁴⁷ The UK Royal College of Obstetricians and Gynaecologists recommends that ventouse birth should be avoided <32⁺⁰ weeks gestation and should be used with caution at 32⁺⁰ to 36⁺⁰ weeks.⁴⁶

#Auditable Standards

To be developed.

#Included guidelines

The search identified thirty guidelines that met criteria for high-quality and/or were recommended for use, none of which primarily addressed mode of birth but all included guidance on this topic within specified indications for preterm birth, although none included statements for assisted vaginal birth.^9-38 Three of the guidelines were assessed to be high-quality in Rigour of Development (score >60%) and in Overall Assessment (score >60%) and were recommended for use in clinical practice by the Review Panel,^9,10 or were recommended for use with modifications.¹¹ All three were national or international guidelines; two relevant to medical conditions contributing to provider-initiated preterm birth^10,11 and one relevant to spontaneous preterm birth.⁹ Eight were assessed to be high-quality in Overall Assessment (score >60%) only and were recommended for use in clinical practice,^12-14 or were recommended with modifications.^15-19 Six of these were national or international guidelines^12-16,19 and two were district health board specific;^17,19 four were relevant to provider-initiated preterm birth,^13,15,18,19 three to multiple pregnancy^14,16,17 and one to birth at the limits of survival.¹² The remaining guidelines did not meet high-quality criteria but were recommended for use with modifications by the Review Panel.^20-38 These included five guidelines relevant to spontaneous preterm birth (all district health board specific);^20-22,29,30 two relevant to multiple pregnancy (one district health board specific and one national/international);^27,28 11 relevant to provider-initiated preterm birth (eight district health board specific and three national/international)^23-26,32-38 and one relevant to birth at limits of survival (district health board specific).³¹

The national ‘Small for Gestational Age / Fetal Growth Restriction Guidelines’³⁹ were published in mid 2023, following the initial literature search. This clinical practice guideline provides an update from the 2014 New Zealand Maternal Fetal Medicine Network guideline that was identified as high-quality in Overall Assessment (score >60%) and suitable for use with modifications by the Review Panel.¹³ Recommendations from the updated 2023 guideline have been considered in this section.

Where high-quality recommendations are not available, additional evidence from recent high-quality studies and systematic reviews has been considered and included as appropriate.

#Impact on equity

Review Panel assessments identified that the recommendations in the guidelines relevant to mode of birth had potential to both reduce and increase differences by equity factors. The potential to increase differences was predominantly related to rural locations and care being provided in smaller units where appropriately experienced staff may be less available. However, recommendations for transfer to regional units providing required level of pregnancy and neonatal care would help to limit these variations. The potential impact of guidelines to improve consistency in care and therefore improve equity was noted for several of these guidelines; appropriate resourcing and implementation will be essential to achieve this.Content for the About tab should be added here.

#Research in progress that may inform future practice recommendations

None identified.

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

Most guidelines referring to mode of birth identified as high-quality and for use in this best practice guide were related to provider-initiated preterm birth with limited guidance on mode of birth. These limited recommendations have been followed, with the exception of the Diagnosis and Treatment of Hypertension and Pre-eclampsia in Pregnancy in New Zealand clinical practice guideline¹⁰ which included a recommendation for mode of birth for wāhine/people with preeclampsia ‘the preferred mode of birth is always vaginal unless it is contraindicated for the mother or the fetus’. This best practice guide is relevant to preterm preeclampsia only, and therefore the recommendation for vaginal birth has been applied in consideration to ‘the majority’.

#References

1. Alfirevic Z, Milan SJ, Livio S. Caesarean section versus vaginal delivery for preterm birth in singletons. Cochrane Database Syst Rev. 2013;6(6):CD000078. DOI: 10.1002/14651858.CD000078.pub2.

2. Grabovac M, Karim J, Isayama T, Liyanage SK, McDonald S. What is the safest mode of birth for extremely preterm breech singleton infants who are actively resuscitated? A systematic review and meta-analyses. BJOG. 2018;125(6):652-63. DOI: 10.1111/1471-0528.14938.

3. Jarde A, Feng YY, Viaje KA, Shah PS, McDonald SD. Vaginal birth vs caesarean section for extremely preterm vertex infants: a systematic review and meta-analyses. Arch Gynecol Obstet. 2020;301(2):447-58. DOI: 10.1007/s00404-019-05417-0.

4. Morrison JJ, Rennie JM, Milton PJ. Neonatal respiratory morbidity and mode of delivery at term: influence of timing of elective caesarean section. BJOG. 1995;102(2):101-6. DOI: 10.1111/j.1471-0528.1995.tb09060.x.

5. Abbott DS, Radford SK, Seed PT, Tribe RM, Shennan AH. Evaluation of a quantitative fetal fibronectin test for spontaneous preterm birth in symptomatic women. Am J Obstet Gynecol. 2013;208(2):122.e1-6. DOI: 10.1016/j.ajog.2012.10.890.

6. Kawakita T, Reddy UM, Grantz KL, Landy HJ, Desale S, Iqbal SN. Maternal outcomes associated with early preterm cesarean delivery. Am J Obstet Gynecol. 2017;216(3):312.e1-.e9. DOI: 10.1016/j.ajog.2016.11.1006.

7. Moramarco V, Korale Liyanage S, Ninan K, Mukerji A, McDonald SD. Classical Cesarean: What Are the Maternal and Infant Risks Compared With Low Transverse Cesarean in Preterm Birth, and Subsequent Uterine Rupture? A Systematic Review and Meta-analysis. J Obstet Gynaecol Can. 2020;42(2):179-97.e3. DOI: 10.1016/j.jogc.2019.02.015.

8. Åberg K, Norman M, Ekéus C. Preterm birth by vacuum extraction and neonatal outcome: a population-based cohort study. BMC Pregnancy Childbirth. 2014;14(1):42. DOI: 10.1186/1471-2393-14-42.

9. World Health Organisation. WHO Recommendations on Interventions to Improve Preterm Birth Outcomes. Geneva: World Health Organisation; 2015. Available from: https://apps.who.int/iris/bitstream/handle/10665/183037/9789241508988\_eng.pdf.

10. Ministry of Health. Diagnosis and Treatment of Hypertension and Pre-eclampsia in Pregnancy in New Zealand: A clinical practice guideline. Wellington: Ministry of Health; 2018. Available from: https://www.health.govt.nz/system/files/documents/publications/diagnosis-and-treatment-of-hypertension-and-pre-eclampsia-in-pregnancy-in-new-zealand-v3.pdf.

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12. Newborn Clinical Network. New Zealand Consensus Statement on the Care of Mother and Baby(ies) at Periviable Gestations. Newborn Clinical Network; 2019. Available from: https://www.starship.org.nz/guidelines/new-zealand-consensus-statement-on-the-care-of-mother-and-baby-ies-at/.

13. New Zealand Maternal Fetal Medicine Network. Guideline for the management of suspected small for gestational age singleton pregnancies and infants after 34 weeks’ gestation. 2014. Available from: https://www.google.com/url?sa=i&rct=j&q=&esrc=s&source=web&cd=&cad=rja&uact=8&ved=0CAMQw7AJahcKEwjI687Fiev6AhUAAAAAHQAAAAAQAw&url=https%3A%2F%2Fwww.healthpoint.co.nz%2Fdownloadinfo%2C138318%2CotherList%2Cqrxtiaam6ix6f02q5yd3.do&psig=AOvVaw1elFB1d9ZGmj4KsXC5K0hy&ust=1666226870943351.

14. The Royal Australian and New Zealand College of Obstetricians and Gynaecologists. Management of monochorionic twin pregnancy. 2021. Available from: https://ranzcog.edu.au/wp-content/uploads/2022/05/Management-of-Monochorionic-Twin-Pregnancy.pdf.

15. Brown MA, Magee LA, Kenny LC, Karumanchi SA, McCarthy FP, Saito S, et al. Hypertensive Disorders of Pregnancy: ISSHP Classification, Diagnosis, and Management Recommendations for International Practice. Hypertension. 2018;72(1):24-43. DOI: 10.1161/hypertensionaha.117.10803.

16. Khalil A, Rodgers M, Baschat A, Bhide A, Gratacos E, Hecher K, et al. ISUOG Practice Guidelines: role of ultrasound in twin pregnancy. Ultrasound Obstet Gynecol. 2016;47(2):247-63. DOI: 10.1002/uog.15821.

17. Waikato District Health Board. Management of Women with Twin Pregnancies. Hamilton: Waikato District Health Board; 2020.

18. 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.

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

20. Auckland District Health Board. Rupture of Membranes in Pregnancy. Auckland: Auckland District Health Board; 2021.

21. Hutt Valley District Health Board. Preterm pre-labour rupture of membranes. Hutt Valley: Hutt Valley District Health Board; 2021.

22. Waikato District Health Board. Rupture of Membranes in Pregnancy. Hamilton: Waikato District Health Board; 2017.

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26. Royal College of Obstetricians and Gynaecologists. The Investigation and Management of the Small-for-Gestational-Age Fetus. 2014. Available from: https://www.rcog.org.uk/media/t3lmjhnl/gtg\_31.pdf.

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28. New Zealand Maternal Fetal Medicine Network. Multiple Pregnancy. 2015. Available from: https://www.tewhatuora.govt.nz/assets/For-the-health-sector/Maternity-Services/Multiple-Pregnancy.pdf.

29. Auckland District Health Board. Preterm Labour - Management of Threatened and Active Preterm Labour. Auckand: Auckland District Health Board; 2021. Available from: https://nationalwomenshealth.adhb.govt.nz/assets/Womens-health/Documents/Policies-and-guidelines/Preterm-Labour-PTL-Management-of-Threatened-and-Active-PTL.pdf.

30. Counties Manukau District Health Board. Preterm Labour Antenatal management of women at high risk of Preterm Birth, management of threatened and acute Preterm Labour (including cervical cerclage insertion). Auckland: Counties Manukau District Health Board; 2020.

31. Counties Manukau District Health Board. Extreme Preterm Birth at 22 to 25+6 weeks. Auckland: Counties Manukau District Health Board; 2021.

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

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

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

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

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

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

38. 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.

39. Te Whatu Ora - Health New Zealand. Small for Gestational Age / Fetal Growth Restriction Guidelines. Wellington: Te Whaut Ora – Healh New Zealand; 2023. Available from: https://www.tewhatuora.govt.nz/publications/small-for-gestational-age-fetal-growth-restriction-guidelines/.

40. SGA/FGR Guideline Development Panel. Small for gestational age and fetal growth restriction in Aotearoa New Zealand: A clinical practice guideline - Draft for consultation. 2022.

41. Jansen C, de Mooij Y, Blomaard C, Derks J, van Leeuwen E, Limpens J, et al. Vaginal delivery in women with a low-lying placenta: a systematic review and meta-analysis. BJOG. 2019;126(9):1118-26. DOI: 10.1111/1471-0528.15622.

42. Barrett JFR, Hannah ME, Hutton EK, Willan AR, Allen AC, Armson BA, et al. A Randomized Trial of Planned Cesarean or Vaginal Delivery for Twin Pregnancy. N Engl J Med. 2013;369(14):1295-305. DOI: 10.1056/NEJMoa1214939.

43. Asztalos EV, Hannah ME, Hutton EK, Willan AR, Allen AC, Armson BA, et al. Twin Birth Study: 2-year neurodevelopmental follow-up of the randomized trial of planned cesarean or planned vaginal delivery for twin pregnancy. Am J Obstet Gynecol. 2016;214(3):371.e1-.e19. DOI: 10.1016/j.ajog.2015.12.051.

44. Aviram A, Lipworth H, Asztalos EV, Mei-Dan E, Melamed N, Cao X, et al. Delivery of monochorionic twins: lessons learned from the Twin Birth Study. Am J Obstet Gynecol. 2020;223(6):916.e1-.e9. DOI: 10.1016/j.ajog.2020.06.048.

45. Verma GL, Spalding JJ, Wilkinson MD, Hofmeyr GJ, Vannevel V, F. OM. Instruments for assisted vaginal birth. Cochrane Database Syst Rev. 2021(9):CD005455. DOI: 10.1002/14651858.CD005455.pub3.

46. Murphy D, Strachan B, Bahl R. Assisted Vaginal Birth. BJOG. 2020;127(9):e70-e112. DOI: 10.1111/1471-0528.16092.

47. The Royal Australian and New Zealand College of Obstetricians and Gynaecologists. Instrumental vaginal birth. 2020. Available from: https://ranzcog.edu.au/wp-content/uploads/2022/05/Instrumental-vaginal-birth.pdf.