O&G · Neonatal care — outcomes of prematurity
Outcomes of prematurity the obstetrician must know
Also known as Prematurity outcomes · Periviability counselling · Survival of preterm infants · Disability after prematurity · Obstetric levers in prematurity · ANZNN outcomes
Exam-exhaustive FRANZCOG fellowship reference on the outcomes of prematurity the obstetrician must own — survival and disability by completed week from the ANZNN reports via the unit counselling card, the denominator trap that flatters the fetus in utero, the four obstetric levers (antenatal corticosteroids, magnesium sulphate, in-utero transfer, active treatment policy) with the trials that bound each, the periviability counselling script at 22 to 24 weeks, the late-preterm majority, and the equity dimension. ANZ-primary, globally tagged to MRCOG and ABOG.
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Red flags
- Quoting a NICU-admission survival figure to a woman whose fetus is still in utero overstates the chance — her fetus has to survive labour, the first minutes and the transfer before it can be a NICU survivor
- A survival figure has a vintage — disability data from a cohort born a decade or more ago are not the numbers for the baby in front of you
- Letting parents hear 'moderate-to-severe impairment' as catastrophic when the registry definition includes language delay alone
- Obstetrics and neonatology quoting different numbers to the same parents on the same night — agree the script before you walk in
- An elective birth before 39 weeks for maternal convenience — the late preterm and early term brain is substantially smaller than at term, and the population effect is large
- A 'lethal' label on a heterogeneous condition like trisomy 13 or 18 — the prognosis is uncertain, not a single number
It is 22:40. A woman at 23+5 weeks is contracting every four minutes. She has had no steroids. The nearest level III centre is 90 minutes away by road. The question the registrar will ask you in the corridor — "what are this baby's chances?" — is the wrong question, and the right one is harder: "what are this fetus's chances, given what we can change in the next two hours, and how do I say it so the parents can decide?" This topic teaches the numbers from source, the levers that change them, and the counselling script that uses them honestly.[1]
Overview — the denominator trap
The first thing to internalise is that every survival number is the bottom of a funnel, and the woman in front of you is at the top of it. The ANZNN figure for 23-week survival is not a property of her fetus; it is the proportion of 23-week fetuses that survived to discharge home after being admitted to a level III NICU.[1]
The four exclusions that push the ANZNN percentage up:[1]
- Fetal deaths (stillbirths before labour or in labour) are excluded.
- Neonatal deaths on the labour ward are excluded.
- Babies born in level II hospitals that are not transferred to a level III unit are excluded.
- Babies never transferred to a NICU or children's hospital are excluded.[1]
The implication: the survival figure you quote overstates the chance for a fetus still in utero, especially at the threshold where some babies never reach a NICU because they were not offered active treatment.[1]
References13ShowHide
- [1]Rysavy MA, Li L, Bell EF, et al. Between-hospital variation in treatment and outcomes in extremely preterm infants N Engl J Med, 2015.PMID 25946279
- [2]Roberts D, Brown J, Medley N, Dalziel SR Antenatal corticosteroids for accelerating fetal lung maturation for women at risk of preterm birth Cochrane Database Syst Rev, 2017.PMID 28321847
- [3]Crowther CA, Middleton PF, Voysey M, Askie L Assessing the neuroprotective benefits for babies of antenatal magnesium sulphate: An individual participant data meta-analysis PLoS Med, 2017.PMID 28976987
- [4]Crowther CA, Ashwood P, Middleton PF, et al. Prenatal Intravenous Magnesium at 30-34 Weeks' Gestation and Neurodevelopmental Outcomes in Offspring: The MAGENTA Randomized Clinical Trial JAMA, 2023.PMID 37581672
- [5]Tarnow-Mordi W, Morris J, Kirby A, et al. Delayed versus Immediate Cord Clamping in Preterm Infants N Engl J Med, 2017.PMID 29081267
- [6]Gyamfi-Bannerman C, Thom EA, Blackwell SC, et al. Antenatal Betamethasone for Women at Risk for Late Preterm Delivery N Engl J Med, 2016.PMID 26842679
- [7]Sharp M, French N, McMichael J, Campbell C Survival and neurodevelopmental outcomes in extremely preterm infants 22-24 weeks of gestation born in Western Australia J Paediatr Child Health, 2018.PMID 28836705
- [8]Fang JL, Mara KC, Weaver AL, Carey WA Outcomes of outborn extremely preterm neonates admitted to a NICU with respiratory distress Arch Dis Child Fetal Neonatal Ed, 2020.PMID 31079068
- [9]Wood NS, Marlow N, Costeloe K, Gibson AT, Wilkinson AR Neurologic and developmental disability after extremely preterm birth. EPICure Study Group N Engl J Med, 2000.PMID 10933736
- [10]Marlow N, Wolke D, Bracewell MA, Samara M Neurologic and developmental disability at six years of age after extremely preterm birth N Engl J Med, 2005.PMID 15635108
- [11]Shepherd E, Salam RA, Middleton P, et al. Antenatal and intrapartum interventions for preventing cerebral palsy: an overview of Cochrane systematic reviews Cochrane Database Syst Rev, 2017.PMID 28786098
- [12]American College of Obstetricians and Gynecologists and Society for Maternal-Fetal Medicine ACOG Obstetric Care Consensus No. 3: Periviable Birth Obstet Gynecol, 2015.PMID 26488525
- [13]Crowther CA, Harding JE Antenatal Glucocorticoids for Late Preterm Birth? N Engl J Med, 2016.PMID 27050210