Temporal Trends in Late Preterm and Early Term Birth Rates in 6 High-Income Countries in North America and Europe and Association With Clinician-Initiated Obstetric Interventions

Richards, Jeffrey T.; Kramer, Michael S.; Deb-Rinker, Paromita; Rouleau, Jocelyn; Mortensen, Laust Hvas; Gissler, Mika; Morken, Nils‐Halvdan; Skjærven, Rolv; Cnattingius, Sven; Johansson, Stefan; Delnord, Marie; Dolan, Siobhan M.; Morisaki, Naho; Tough, Suzanne; Zeitlin, Jennifer; Kramer, Michael R.

doi:10.1001/jama.2016.9635

Cited by 82 publications

(62 citation statements)

References 33 publications

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“…The gestational age group that increased the most in size in our study was the late preterm group and showed a similar trend to what other studies have found . The late preterm group has been increasing more than the other gestational age groups globally and is over 70% of all preterm births in Norway, Denmark, Sweden, the United States, Canada, and Finland (71%‐76%) . This increase in preterm births at 34‐36 weeks’ gestation seems to have plateaued in the last few years after an increased focus on late preterm births among clinicians and researchers given that the mortality and morbidity are much higher for late preterm than for term infants …”

Section: Discussionsupporting

confidence: 87%

Preterm births in Iceland 1997‐2016: Preterm birth rates by gestational age groups and type of preterm birth

Grétarsdóttir

Aspelund

Steingrímsdóttir

et al. 2019

Birth

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Background The frequency of preterm births has been increasing globally, mainly due to a rise in iatrogenic late preterm births. The aim of this study was to assess the prevalence of preterm births in Iceland during 1997‐2016 by type of preterm birth. Methods This study included all live births in Iceland during 1997‐2016 identified from the Icelandic Medical Birth Registry. Risk of preterm birth by time period was assessed with Poisson regression models adjusted for demographic variables and indications for iatrogenic births. Results The study population included 87 076 infants, of which 4986 (5.7%) were preterm. The preterm birth rate increased from 5.3% to 6.1% (adjusted rate ratio [ARR] = 1.16, confidence interval [CI] = 1.07‐1.26) between 1997‐2001 and 2012‐2016 overall. The increase was only evident in multiples (ARR 1.41, 95% CI 1.21‐1.65), not singletons (1.07, 0.97‐1.19). The rate of late preterm births (34‐36 weeks) increased significantly (1.24, 1.14‐1.40), and the rate of iatrogenic preterm births more than doubled during this period even after adjustment for identified medical indications (2.40, 2.00‐2.88). The rate of spontaneous preterm births decreased during the study period (0.63, 0.55‐0.73), and the rate of PPROM increased (1.31, 1.09‐1.57). The most common contributing indications for iatrogenic births were fetal distress (26.2%), hypertensive disorders (18.2%), and severe preeclampsia (16.9%). Conclusions Preterm birth rates increased in multiples in Iceland between 1997 and 2016, and late and iatrogenic preterm births increased overall. The increase in iatrogenic preterm births remained significant after adjusting for medical indications, suggesting that other factors might be affecting the rise.

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Section: Discussionsupporting

confidence: 87%

Preterm births in Iceland 1997‐2016: Preterm birth rates by gestational age groups and type of preterm birth

Grétarsdóttir

Aspelund

Steingrímsdóttir

et al. 2019

Birth

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“…The rate of provider initiated among early-term births in our study (46.7%) was as high as those previously reported in developed countries, like Canada (45.2%), USA (42.4%) and Denmark (41.8%). 22 However, Brazilian early-term birth rate (35%) was the double of the rates observed in northern countries of Europe, such as Denmark (18.1%), Finland (17.4%), Sweden (18.5%) and Norway (16.8%) and considerably higher than in Canada (25.3%) and the USA (24.4%). 22 Developed countries have prelabour caesarean rates in the early-term group close to 20% (Canada, Denmark, Norway, Sweden, USA), 22 while our study found more than 40%.…”

Section: Discussionmentioning

confidence: 89%

“…In developed countries, the pooled rate of early-term births ranged from 16.8% in Finland to 26.9% in the USA in the period 2006–2014, with decreasing rates in Norway, Sweden and the USA. 22 However, the proportion of early-term births in Brazil and other developing countries is not yet known. Hence, there is a lack of a solid data concerning impact of early-term birth via CS without clinical indication on maternal and neonatal outcomes in countries with high rates of CS.…”

Section: Introductionmentioning

confidence: 99%

Burden of early-term birth on adverse infant outcomes: a population-based cohort study in Brazil

et al. 2017

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ObjectivesTo estimate the national rate of early-term live births in Brazil and to evaluate the effect of birth at 37 and 38 weeks’ gestation, as compared with 39 and 40 weeks’ gestation on infant outcomes according to precursors of birth and the existence of maternal/fetal medical conditions.DesignNational perinatal population-based cohort study.Setting266 maternity services located in the five Brazilian macroregions.Participants18 652 singleton live newborns from 37 0/7 to 40 6/7 weeks of gestation.Main outcome measuresResuscitation in delivery room, oxygen therapy, transient tachypnoea, admission to neonatal intensive care unit (NICU), hypoglycaemia, use of antibiotics, phototherapy, phototherapy after hospital discharge, neonatal death and breastfeeding.ResultsEarly terms accounted for 35% (95% CI 33.4% to 36.7%) of all live births. Among provider-initiated births in women without medical conditions, infants of 37 and 38 weeks’ gestation had higher odds of oxygen therapy (adjusted OR (AOR) 2.93, 95% CI 1.72 to 4.98 and AOR 1.92 95% CI 1.18 to 3.13), along with admission to NICU (AOR 2.01, 95% CI 1.18 to 3.41 and AOR 1.56, 95% CI 1.02 to 2.60), neonatal death (AOR 14.40, 95% CI 1.94 to 106.69 and AOR 13.76,95% CI 2.84 to 66.75), hypoglycaemia in the first 48 hours of life (AOR 7.86, 95% CI 1.95 to 31.71 and AOR 5.76, 95% CI 1.63 to 20.32), transient tachypnoea (AOR 2.98, 95% CI 1.57 to 5.65 and AOR 2.12, 95% CI 1.00 to 4.48) and the need for phototherapy within the first 72 hours of life (AOR 3.59, 95% CI 1.95 to 6.60 and AOR 2.29, 95% CI 1.49 to 3.53), yet lower odds of breastfeeding up to 1 hour after birth (AOR 0.67, 95% CI 0.53 to 0.86 and AOR 0.87, 95% CI 0.76 to 0.99) and exclusive breastfeeding during hospital stay (AOR 0.68, 95% CI 0.51 to 0.89 and AOR 0.84, 95% CI 0.71 to 0.99).ConclusionBirth at 37 and 38 weeks’ gestation increased the risk of most adverse infant outcomes analysed, especially among provider-initiated births and should be avoided before 39 weeks’ gestation in healthy pregnancies.

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“…However, despite the significant public health burden, 4 9–11 little progress has been made in decreasing the number of these early births. 6 12 13 The latest French recommendations for the prevention of spontaneous preterm birth (sPTB) focus on smoking cessation and on interventions for women with high-risk pregnancies (ie, cerclage, progesterone), but conclude that high-quality evidence does not exist for other preventive strategies 14 ; this is partially due to the low predictive accuracy of diagnostic tools. 12 As for early-term birth, prevention efforts are recent, with a focus by professional societies in the USA on the reduction of indicated early-term deliveries for non-medical reasons.…”

Section: Introductionmentioning

confidence: 99%

Are risk factors for preterm and early-term live singleton birth the same? A population-based study in France

et al. 2018

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ObjectivesTo investigate whether risk factors for preterm (<37 weeks gestation) and early-term birth (37 and 38 weeks gestation) are similar.DesignNationally representative cross-sectional study of births.SettingFrance in 2010.ParticipantsLive singleton births (n=14 326).Primary and secondary outcome measuresPreterm and early-term birth rates overall and by mode of delivery (spontaneous and indicated). Risk factors were maternal sociodemographic characteristics, previous preterm birth, height, prepregnancy body mass index (BMI) and smoking, assessed using multinomial regression models with full-term births 39 weeks and over as the reference group.ResultsThere were 5.5% preterm and 22.5% early-term births. Common risk factors were: a previous preterm delivery (adjusted relative risk ratio (aRRR) 8.2 (95% CI 6.2 to 10.7) and aRRR 2.4 (95% CI 2.0 to 3.0), respectively), short stature, underweight (overall and in spontaneous deliveries), obesity (in indicated deliveries only), a low educational level and Sub-Saharan African origin. In contrast, primiparity was a risk factor only for preterm birth, aRRR 1.8 (95% CI 1.5 to 2.2), while higher parity was associated with greater risk of early-term birth.ConclusionsMost population-level risk factors were common to both preterm and early-term birth with the exception of primiparity, and BMI which differed by mode of onset of delivery. Our results suggest that preterm and early-term birth share similar aetiologies and thus potentially common strategies for prevention.

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Temporal Trends in Late Preterm and Early Term Birth Rates in 6 High-Income Countries in North America and Europe and Association With Clinician-Initiated Obstetric Interventions

Cited by 82 publications

References 33 publications

Preterm births in Iceland 1997‐2016: Preterm birth rates by gestational age groups and type of preterm birth

Preterm births in Iceland 1997‐2016: Preterm birth rates by gestational age groups and type of preterm birth

Burden of early-term birth on adverse infant outcomes: a population-based cohort study in Brazil

Are risk factors for preterm and early-term live singleton birth the same? A population-based study in France

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