Marie Delnord

What contributes to disparities in the preterm birth rate in European countries

Purpose of review In countries with comparable levels of development and healthcare systems, preterm birth rates vary markedly – a range from 5 to 10% among live births in Europe. This review seeks to identify the most likely sources of heterogeneity in preterm birth rates, which could explain differences between European countries. Recent findings Multiple risk factors impact on preterm birth. Recent studies reported on measurement issues, population characteristics, reproductive health policies as well as medical practices, including those related to subfertility treatments and indicated deliveries, which affect preterm birth rates and trends in high-income countries. We showed wide variation in population characteristics, including multiple pregnancies, maternal age, BMI, smoking, and percentage of migrants in European countries. Summary Many potentially modifiable population factors (BMI, smoking, and environmental exposures) as well as health system factors (practices related to indicated preterm deliveries) play a role in determining preterm birth risk. More knowledge about how these factors contribute to low and stable preterm birth rates in some countries is needed for shaping future policy. It is also important to clarify the potential contribution of artifactual differences owing to measurement.

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

IMPORTANCE Clinicians have been urged to delay the use of obstetric interventions (eg, labor induction, cesarean delivery) until 39 weeks or later in the absence of maternal or fetal indications for intervention. OBJECTIVE To describe recent trends in late preterm and early term birth rates in 6 high-income countries and assess association with use of clinician-initiated obstetric interventions. DESIGN Retrospective analysis of singleton live births from 2006 to the latest available year (ranging from 2010 to 2015) in Canada, Denmark, Finland, Norway, Sweden, and the United States. EXPOSURES Use of clinician-initiated obstetric intervention (either labor induction or prelabor cesarean delivery) during delivery. MAIN OUTCOMES AND MEASURES Annual country-specific late preterm (34-36 weeks) and early term (37-38 weeks) birth rates. RESULTS The study population included 2,415,432 Canadian births in 2006-2014 (4.8% late preterm; 25.3% early term); 305,947 Danish births in 2006-2010 (3.6% late preterm; 18.8% early term); 571,937 Finnish births in 2006-2015 (3.3% late preterm; 16.8% early term); 468,954 Norwegian births in 2006-2013 (3.8% late preterm; 17.2% early term); 737,754 Swedish births in 2006-2012 (3.6% late preterm; 18.7% early term); and 25,788,558 US births in 2006-2014 (6.0% late preterm; 26.9% early term). Late preterm birth rates decreased in Norway (3.9% to 3.5%) and the United States (6.8% to 5.7%). Early term birth rates decreased in Norway (17.6% to 16.8%), Sweden (19.4% to 18.5%), and the United States (30.2% to 24.4%). In the United States, early term birth rates decreased from 33.0% in 2006 to 21.1% in 2014 among births with clinician-initiated obstetric intervention, and from 29.7% in 2006 to 27.1% in 2014 among births without clinician-initiated obstetric intervention. Rates of clinician-initiated obstetric intervention increased among late preterm births in Canada (28.0% to 37.9%), Denmark (22.2% to 25.0%), and Finland (25.1% to 38.5%), and among early term births in Denmark (38.4% to 43.8%) and Finland (29.8% to 40.1%). CONCLUSIONS AND RELEVANCE Between 2006 and 2014, late preterm and early term birth rates decreased in the United States, and an association was observed between early term birth rates and decreasing clinician-initiated obstetric interventions. Late preterm births also decreased in Norway, and early term births decreased in Norway and Sweden. Clinician-initiated obstetric interventions increased in some countries but no association was found with rates of late preterm or early term birth.

Variations in very preterm birth rates in 30 high-income countries: are valid international comparisons possible using routine data?

Concerns about differences in registration practices across countries have limited the use of routine data for international very preterm birth (VPT) rate comparisons.

Risk factors of preterm birth in France in 2010 and changes since 1995: Results from the French National Perinatal Surveys

OBJECTIVES To investigate risk factors of total, spontaneous and induced preterm birth in 2010 and differences between 1995 and 2010. MATERIAL AND METHODS The national perinatal surveys are based on a representative sample of births in France. We selected live-born singletons (n=14,326 in 2010 and 12,885 in 1995) and used multiple regression analyses to calculate adjusted odds ratios (aOR) for maternal sociodemographic characteristics, obstetric history, prenatal care and smoking. RESULTS The main risk factors in 2010 were parity 1 compared to parity 2 (aOR=1.9 [95% CI 1.5-1.3]), previous preterm delivery (aOR=6.6 [5.0-8.7]), pre-pregnancy body mass index<18.5 compared to 18.5-24.9kg/m2 (aOR=1.7 [1.4-2.2]), level of education completed: high school or less, inadequate prenatal care and cannabis use. Most risk factors of spontaneous and induced preterm births were similar. Compared to 1995, maternal age≥35 years and previous induced abortion were no longer associated with preterm birth in 2010. CONCLUSION Identified risk factors for preterm birth in France in 2010 agree with the literature. Increases in baseline rates for maternal age and medically induced abortions may explain changes in certain preterm birth risk factors.OBJECTIVES To investigate risk factors of total, spontaneous and induced preterm birth in 2010 and differences between 1995 and 2010. MATERIAL AND METHODS The national perinatal surveys are based on a representative sample of births in France. We selected live-born singletons (n=14,326 in 2010 and 12,885 in 1995) and used multiple regression analyses to calculate adjusted odds ratios (aOR) for maternal sociodemographic characteristics, obstetric history, prenatal care and smoking. RESULTS The main risk factors in 2010 were parity 1 compared to parity 2 (aOR=1.9 [95% CI 1.5-1.3]), previous preterm delivery (aOR=6.6 [5.0-8.7]), pre-pregnancy body mass index<18.5 compared to 18.5-24.9kg/m2 (aOR=1.7 [1.4-2.2]), level of education completed: high school or less, inadequate prenatal care and cannabis use. Most risk factors of spontaneous and induced preterm births were similar. Compared to 1995, maternal age≥35 years and previous induced abortion were no longer associated with preterm birth in 2010. CONCLUSION Identified risk factors for preterm birth in France in 2010 agree with the literature. Increases in baseline rates for maternal age and medically induced abortions may explain changes in certain preterm birth risk factors.

Linking databases on perinatal health: a review of the literature and current practices in Europe

Background: International comparisons of perinatal health indicators are complicated by the heterogeneity of data sources on pregnancy, maternal and neonatal outcomes. Record linkage can extend the range of data items available and thus can improve the validity and quality of routine data. We sought to assess the extent to which data are linked routinely for perinatal health research and reporting. Methods: We conducted a systematic review of the literature by searching PubMed for perinatal health studies from 2001 to 2011 based on linkage of routine data (data collected continuously at various time intervals). We also surveyed European health monitoring professionals about use of linkage for national perinatal health surveillance. Results: 516 studies fit our inclusion criteria. Denmark, Finland, Norway and Sweden, the US and the UK contributed 76% of the publications; a further 29 countries contributed at least one publication. Most studies linked vital statistics, hospital records, medical birth registries and cohort data. Other sources were specific registers for: cancer (70), congenital anomalies (56), ART (19), census (19), health professionals (37), insurance (22) prescription (31), and level of education (18). Eighteen of 29 countries (62%) reported linking data for routine perinatal health monitoring. Conclusion: Research using linkage is concentrated in a few countries and is not widely practiced in Europe. Broader adoption of data linkage could yield substantial gains for perinatal health research and surveillance.

International variations in the gestational age distribution of births: an ecological study in 34 high-income countries

Background Few studies have investigated international variations in the gestational age (GA) distribution of births. While preterm births (22-36 weeks GA) and early term births (37-38 weeks) are at greater risk of adverse health outcomes compared to full term births (39-40 weeks), it is not known if countries with high preterm birth rates also have high early term birth rates. We examined rate associations between preterm and early term births and mean term GA by mode of delivery onset. Methods We used routine aggregate data on the GA distribution of singleton live births from up to 34 high-income countries/regions in 1996, 2000, 2004, 2008 and 2010 to study preterm and early term births overall and by spontaneous or indicated onset. Pearson correlation coefficients were adjusted for clustering in time trend analyses. Results Preterm and early term births ranged from 4.1% to 8.2% (median 5.5%) and 15.6% to 30.8% (median 22.2%) of live births in 2010, respectively. Countries with higher preterm birth rates in 2004-2010 had higher early term birth rates (r > 0.50, P < 0.01) and changes over time were strongly correlated overall (adjusted-r = 0.55, P < 0.01) and by mode of onset. Conclusion Positive associations between preterm and early term birth rates suggest that common risk factors could underpin shifts in the GA distribution. Targeting modifiable population risk factors for delivery before 39 weeks GA may provide a useful preterm birth prevention paradigm.

Quantifying the burden of stillbirths before 28 weeks of completed gestational age in high-income countries: a population-based study of 19 European countries

BACKGROUND International comparisons of stillbirth allow assessment of variations in clinical practice to reduce mortality. Currently, such comparisons include only stillbirths from 28 or more completed weeks of gestational age, which underestimates the true burden of stillbirth. With increased registration of early stillbirths in high-income countries, we assessed the reliability of including stillbirths before 28 completed weeks in such comparisons. METHODS In this population-based study, we used national cohort data from 19 European countries participating in the Euro-Peristat project on livebirths and stillbirths from 22 completed weeks of gestation in 2004, 2010, and 2015. We excluded countries without national data for stillbirths by gestational age in these periods, or where data available were not comparable between 2004 and 2015. We also excluded those countries with fewer than 10 000 births per year because the proportion of stillbirths at 22 weeks to less than 28 weeks of gestation is small. We calculated pooled stillbirth rates using a random-effects model and changes in rates between 2004 and 2015 using risk ratios (RR) by gestational age and country. FINDINGS Stillbirths at 22 weeks to less than 28 weeks of gestation accounted for 32% of all stillbirths in 2015. The pooled stillbirth rate at 24 weeks to less than 28 weeks declined from 0·97 to 0·70 per 1000 births from 2004 to 2015, a reduction of 25% (RR 0·75, 95% CI 0·65-0·85). The pooled stillbirth rate at 22 weeks to less than 24 weeks of gestation in 2015 was 0·53 per 1000 births and did not significantly changed over time (RR 0·97, 95% CI 0·80-1·16) although changes varied widely between countries (RRs 0·62-2·09). Wide variation in the percentage of all births occurring at 22 weeks to less than 24 weeks of gestation suggest international differences in ascertainment. INTERPRETATION Present definitions used for international comparisons exclude a third of stillbirths. International consistency of reporting stillbirths at 24 weeks to less than 28 weeks suggests these deaths should be included in routinely reported comparisons. This addition would have a major impact, acknowledging the burden of perinatal death to families, and making international assessments more informative for clinical practice and policy. Ascertainment of fetal deaths at 22 weeks to less than 24 weeks should be stabilised so that all stillbirths from 22 completed weeks of gestation onwards can be reliably compared. FUNDING EU Union under the framework of the Health Programme and the Bridge Health Project.

Can the Apgar Score be Used for International Comparisons of Newborn Health

BACKGROUND The Apgar score has been shown to be predictive of neonatal mortality in clinical and population studies, but has not been used for international comparisons. We examined population-level distributions in Apgar scores and associations with neonatal mortality in Europe. METHODS Aggregate data on the 5 minute Apgar score for live births and neonatal mortality rates from countries participating in the Euro-Peristat project in 2004 and 2010 were analysed. Country level associations between the Apgar score and neonatal mortality were assessed using the Spearman rank correlation coefficient. RESULTS Twenty-three countries or regions provided data on Apgar at 5 minutes, covering 2 183 472 live births. Scores <7 ranged from 0.3% to 2.4% across countries in 2004 and 2010 and were correlated over time (ρ = 0.88, P < 0.01). There were large differences in healthy baby scores: scores of 10 ranged from 8.8% to 92.7% whereas scores of 9 or 10 ranged from 72.9% to 96.8%. Countries more likely to score 10 s, as opposed to 9 s, for healthy babies had lower proportions of Apgar <7 (ρ = -0.43, P = 0.04). Neonatal mortality rates were weakly correlated with Apgar score <7 (ρ = -0.06, P = 0.61), but differences over time in these two indicators were correlated (ρ =0.56, P = 0.02). CONCLUSIONS Large variations in the distribution of Apgar scores likely due to national scoring practices make the Apgar score an unsuitable indicator for benchmarking newborn health across countries. However, country-level trends over time in the Apgar score may reflect real changes and merit further investigation.

Epidemiology of late preterm and early term births – An international perspective

Late preterm (34-36 weeks of gestational age (GA)), and early term (37-38 weeks GA) birth rates among singleton live births vary from 3% to 6% and from 15% to 31%, respectively, across countries, although data from low- and middle-income countries are sparse. Countries with high preterm birth rates are more likely to have high early term birth rates; many risk factors are shared, including pregnancy complications (hypertension, diabetes), medical practices (provider-initiated delivery, assisted reproduction), maternal socio-demographic and lifestyle characteristics and environmental factors. Exceptions include nulliparity and inflammation which increase risks for preterm, but not early term birth. Birth before 39 weeks GA is associated with adverse child health outcomes across a wide range of settings. International rate variations suggest that reductions in early delivery are achievable; implementation of best practice guidelines for obstetrical interventions and public health policies targeting population risk factors could contribute to prevention of both late preterm and early term births.

Authors' reply re: Variations in very preterm birth rates in 30 high‐income countries: are valid international comparisons possible using routine data?

The paper of Delnord et al. presents a dilemma in using routinely collected gestational age (GA) data especially regarding the inclusion of births at 22– 23 weeks GA for international comparisons of very preterm (VPT) birth rates. In this paper VPT birth data from European countries were collected for the year 2010. As Croatia was not yet a member of the European Union, we would like to compare Croatian VPT birth data from the national medical birth register with the presented findings. From 2001 onwards, data on all live births (LB), irrespective of birthweight (BW) andGA, and stillbirths (SB) ≥22 weeks of GA or BW ≥500 g have been reported for routine health statistics, in contrast to national vital statistics data for LB, which were collected irrespective ofGAandBW. Nonetheless, data from the medical birth register were similar to vital statistics for 99.9% of births. A total of 43 419newbornswere born in the year 2010 in Croatia. Among 41 024 singletons with known GA, there were 315 VPTbirths: 0.6& (15LBand 10SB) at 22– 23 weeks, 2.6& (83 LB and 25 SB) at 24– 27 weeks, and 4.5& (149 LB and 33 SB) at 28–31 weeks of GA. In 2010 for the 30 countries described by Delnord et al. there were 106 793 VPT singleton births with averages as follows: 0.9& for 22– 23 weeks of GA, 2.8& for 24–27 weeks of GA and 4.9& for 28–31 weeks of GA. The VPT birth rate in 2010 in Croatia was 7.7/1000 total births, whereas the median singleton VPT rate among the 30 high-income countries analysed was 9.5 per 1000 births. Croatian rates were below the 25th centile (Q1 = 8.5&) as in Iceland, Finland, Japan, Sweden, Italy, Slovakia, Norway and Malta. The proportion of periviable births (22– 23 weeks GA) among all VPT births in Croatia was 7.9%, whereas Delnord et al. found variations of proportions between 0.7 and 23.4% among 30 countries. Stillbirths constituted 21.6% of all VPT births in Croatia, similar to the 20.6% average of the 30 analysed countries. After exclusion of periviable births (25), the percentage of SB among VPT births was 20.0%, only a slight difference from rates including VPT births at 22– 23 weeks of GA. So, exclusion of periviable births from our results would not substantially influence the VPT birth rate. Data collected in Croatia represent the example of possible valid comparisons even when using routinely collected data since 2001, using World Health Organization (International Classification of Diseases, 9th revision) (WHO ICD-9) and the International Federation of Gynecology and Obstetrics (FIGO) (≥22 weeks GA) recommendations from 1979 to 1982, respectively. Although, the results of Delnord et al. indicated possible difficulties in comparisons of the VPT birth rates, it would be preferable to establish common rules for collecting all birth data, including VPT birth data. Results from the Euro-Peristat Project should encourage national agencies to collect data following the WHO ICD-9 and FIGO recommendations. Goldenberg and McClure also strongly suggest collecting all perinatal outcome data irrespective of GA or BW, whether born alive or stillbirth.&