the late preterm infant -outcomes simon rowley august 2011
TRANSCRIPT
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The Late Preterm Infant -Outcomes
Simon Rowley
August 2011
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Who is the late preterm?
• 34 weeks 0 days through 36 weeks 6 days after last menstrual period
• The lower limit used because it is a frequent cut-off point for obstetric decision making and as a criteria for admission to a level 2 or level 3 NICU
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Overview of talk
• The rise in Preterm rates• Physiological changes in the last weeks of pregnancy• Morbidities in the late preterm infant• Short term outcomes -respiratory• Long-term developmental and behavioural outcomes in
the preterm infant• Long term cardiovascular and diabetes risk• Costs to society• Implications for obstetric practice• Parents perceptions of illness severity in their baby
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Complications of the Late Preterm Infant –Darcy J Perinat Nursing Vol 23 No 1 PP 78-86. 2009
• The incidence of prematurity continues to rise• Late preterm infants (34-36 wks) comprise the
fastest growing population and account for more than 70% of all preterm births and 8.5% of all births in the USA(2005)
• Generally less studied as a group• Morbidity and mortality higher than expected• The newborn risk in late preterm population is
under appreciated
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Survival AT NWH 1959-2003
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Late preterm admissionsACH NICU 2004-2008
• 4169 total admissions
• 1185 infants admitted 34-36weeks
• this is 28.5% of total admissions
• RDS the main diagnosis other than prematurity
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National Institute of Child Health and Human
Development Workshop July 2005 –Tonse, Raju et al. Pediatrics 2006;118;1207-1214
• Preterm births in US ↑ 9.1% in 1981 to 12.3% in 2003
• Most of the increase is in proportion of late preterm births (Davidoff et al Semin Perinatol 2006)
• Underscored the need to educate healthcare providers and parents about the vulnerability of late preterm infants
• ‘These infants need diligent evaluation, monitoring, referral, and early return appointments not only for post-natal evaluation but also for continued long term follow-up’
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Increase in Late Preterm births
• Increased reproductive technology and multi-fetal pregnancies
• Advance in obstetric practice with increased surveillance and medical interventions in pregnancy
• electronic fetal monitoring increased between 1989-2003 from 68-85% and labour inductions and LSCS increased correspondingly
• Changing maternal profile –teenage mothers, increasing maternal age, obesity, gestational diabetes
• Possible approach of clinicians to the late preterm infant as being similar to the term infant post-natally
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What happens to the late preterm infant after birth?
• Resuscitation• Transition• Separation from
parents• Admission to NICU• Invasive procedures• Respiratory support• Phototherapy
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Developmental and Physiological Immaturity of Late Preterm Infants 1
• From 34.0-36.9 weeks gestation• Terminal respiratory units-alveolar saccules
become lined with cuboidal type 2 and flat type 1 epithelial cells become mature alveoli lined with extremely thin type 1 alveolar cells
• Pulmonary capillaries bulge into each terminal sac
• Adult pool sizes of surfactant attained
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Developmental and Physiological Immaturity of Late Preterm Infants 2
• Apnoea incidence 4-7% (less than 1% at term)• Mechanism –central -the brain is
developmentally less mature with fewer sulci and gyri and less myelin. The brain at 34 weeks is approximately 2/3 size at term
• -other - ↓ susceptibility to hypoxic resp. depression, ↓chemo-sensitivity to CO2, ↑resp.inhibition sensitivity to laryngeal stimulation, ↓ upper airway dilator muscle tone
(all these are SUDI risks)
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Developmental and Physiological Immaturity of Late Preterm Infants 3
• Cardiovascular structural and functional immaturity restricts reserve during stress.
• Delayed ductal closure and persistent pulmonary hypertension(or delayed transition) more likely
• Brown fat accumulation, maturation and accumulation of hormones resposible for brown fat metabolism ( prolactin, leptin, NA, T3, cortisol) peak at term
• Less white adipose tissue, cannot generate heat as effectively from brown adipose tissue as effectively as term infants
• Larger SA/body weight ratio increases heat loss
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Developmental and Physiological Immaturity of Late Preterm Infants 4
• Hypoglycaemia inversely proportional to gestational age
• Glycogen stores double at 36w gestation, in preparation for birth, and are rapidly depleted within the first 24 hours of life
• Immature hepatic glycogenolysis, adipose tissue lipolysis, hormonal dys-regulation, deficient hepatic gluco-neogenesis and keto-genesis
• Therefore blood glucose drops to nadir at 1-2 hours until alternative pathways activated or exogenous glucose supplied
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Developmental and Physiological Immaturity of Late Preterm Infants 5
• Jaundice more common. Late preterms 2 times more likely to have significantly elevated SBR and persisting 5-7 days
• Lower concentrations of UDPG glucuronosyl-transferase
• Enterohepatic circulation secondary to delayed gut motility and feeding
• Risk of kernicterus increased at lower gestations• Hyperbilirubinaemia the most common reason
for re-admission
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Do Late Preterm Infants Breast Feed?
Australian longitudinal study: Donath et al. Arch Dis Child Fetal Neonatal Ed 2008.93.448-450
• 35-36 weeks 88.2% breast feeding initiation rate• 41% still breast feeding at 6 months age
• 37-39 weeks 92.0% initiation rate • 54.5% still breast feeding at 6months
• Term infants 93.9% initiation rate • - 60.5% still breast feeding at 6 months
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Kernicterus in Late Preterm Infants Cared for as Term Healthy Infants. Bhutani,
Semin Perinatol 2006; 30:89-97
125 cases in US, 1979 – 2002 “healthy at discharge” Sources – parents, MDs RNs, literature, med-legal 69% male Nearly all breastfed [follow up scheduled for 2 weeks] 97% discharge <72 h (58% < 48 h) 25% Late Preterm infants LGA with kernicterus
35% Late Preterm infants were LGA* 25% Term infants were LGA*
Kernicterus RegistryIncidence & Patient Profile
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The contribution of Mild and moderate Preterm birth to Infant mortality Kramer et al
JAMA vol 284 no 7 Aug 16 2000
• Landmark study • Looked at quantitative contribution of mild (34-36)
preterm birth to infant mortality• Large cohort of US and Canadian births for years 1985
and 1995 (US) and 1985-7 and 1992-4 (Canada)• RR for deaths from all causes at 34-36 wks gestation
was 2.9 (CI 2.8-3.0) in US and 4.5 ( CI 4.0-5.0) in Canada
• Early neonatal, late neonatal and post neonatal deaths contributed 9/1000 livebirths
• Postnatal causes included infection,SIDS and external causes( NAI and accidental deaths)
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Perinatal Outcomes Associated with Preterm Birth at 33 to 36 Weeks’ Gestation: A Population-Based Cohort Study :
Khasu et al Pediatrics 2009; 123
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Respiratory Morbidity and Lung Function in Preterm Infants of 32 to 36 Weeks’ gestational Age
Colin et al Pediatrics 2010;115-128
• Comprehensive search for studies reporting epidemiologic data and respiratory morbidity in infants 34-36 weeks
• 24 studies identified• Consistent finding that babies born at 34-36 weeks
experience substantial respiratory morbidity compared with term infants.
• Levels of morbidity at times equalled that of very preterm infants
• Longitudinal studies indicate that this reduced level of pulmonary function early on persists into early adulthood
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Decreased expiratory flow in infants who were healthy late
preterms
Colin et al Pediatrics 2010; 126: 115-128
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Respiratory Morbidity and Lung Function in Preterm Infants of 32 to 36 Weeks’ gestational Age
Colin et al Pediatrics 2010;115-128
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Short Term Outcomes of Infants Born at 35 and 36 Weeks Gestation: We Need to Ask More Questions. Escobar et al. Semin Perinatol
30:28-33 2006
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NWH Data
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RDS incidence related to gestation in late preterm infants
• 33-34 weeks 12%• 35-36 weeks 2%• Term 0.11%
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Risk of respiratory morbidity in term infants delivered by elective LSCS: cohort study
Hansen et al. BMJ Online March 2008
• 2687 infants out of total 34458 delivered by elective LSCS in years 1998-2006
• Main outcome respiratory morbidity (TTN, RDS, PPHTNB, serious resp. morbidity (oxygen more than 2 days, CPAP or IPPV) in LSCS compared to vaginal delivery
• At 37 wks ↑ resp morbidity OR 3.9(2.4-6.5)• At 38 wks resp morbidity OR 3.0( 2.1-4.3)• At 37 wks serious morbidity ↑ 5 fold OR 5.0(1.6-16)• Results unchanged after exclusion of pregnancies
complicated by diabetes, pre-eclampsia IUGR, or breech
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Incidence of Early Neonatal Mortality and Morbidity After Late Preterm and Term
Cesarian Delivery De Luca et al Pediatrics vol 123 no. 6 2009
• GA specific risk estimates are lowest between 38-40 weeks and should be included in the consent process
• Elective cesarian delivery is consistently associated with increased intrapartum and neonatal mortality, risk of admission, and respiratory morbidity compare to planned vaginal delivery
• No advantage of PVD over emergency cesarian delivery
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Incidence of Early Neonatal Mortality and Morbidity After Late Preterm and Term
Caesarian Delivery De Luca et al Pediatrics vol 123 no. 6 2009
Special Care admissions
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Incidence of Early Neonatal Mortality and Morbidity After Late Preterm and Term
Caesarian Delivery De Luca et al Pediatrics vol 123 no. 6 2009
Respiratory morbidity
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Incidence of Early Neonatal Mortality and Morbidity After Late Preterm and Term
Caesarian Delivery De Luca et al Pediatrics vol 123 no. 6 2009
Elective Cesarian vs Planned Vaginal Delivery
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Getting evidence into obstetric practice; appropriate timing of caesarian section
Nicholl and Cattell Australian Health review 2010,34,90-92
• Aim: to reduce rate of term elective CS with no medical indication before 39 completed weeks, from 30% to 10% of all term elective CS (both private and public) over a 6 month period in 2007
• Method: multidisciplinary project formed to investigate the extent of the problem and work out the intervention which was essentially pre-emptive education of all midwifery and obstetric staff and provision of evidence folders in key clinical areas
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Perinatal Outcomes Associated with Preterm Birth at 33 to 36 Weeks’ Gestation: A Population-Based Cohort Study :
Khasu et al Pediatrics 2009; 123