Determination of birth-weight centile thresholds associated with adverse perinatal outcomes using population, customised, and Intergrowth charts: A Swedish population-based cohort study

Abstract

BackgroundAlthough many studies have compared birth-weight charts to determine which better identify infants at risk of adverse perinatal outcomes, less attention has been given to the threshold used to define small or large for gestational age (SGA or LGA) infants. Our aim was to explore different thresholds associated with increased risk of adverse perinatal outcomes using population, customised, and Intergrowth centile charts.Methods and findingsThis is a population-based cohort study (Swedish Medical Birth Registry), which included term singleton births between 2006 and 2015 from women with available data on first-trimester screening. Population, customised, and Intergrowth charts were studied. Outcomes included cesarean section, postpartum haemorrhage, severe perineal tear, Apgar score at 5 minutes, neonatal morbidity, and perinatal mortality. Odds for each outcome were assessed in intervals of 5 centiles of birth weight (reference being 40th–60th centiles) using logistic regression. Intervals of 5% of the population were also explored. Sensitivity for fixed false-positive rates (FPRs) was reported for neonatal outcomes. Data from 212,101 births were analysed. Mean age was 33 ± 5 years, 48% of women were nulliparous, and 80% were born in Sweden. Prevalence of SGA (<10th centile) was 10.1%, 10.0%, and 3.1%, and prevalence of LGA (>90th centile) was 10.0%, 8.2%, and 25.1%, assessed using population, customised, and Intergrowth charts, respectively. In small infants, the risk of perinatal mortality was consistently increased below the 15th, 10th, and 35th birth-weight centiles for the respective charts (odds ratio [OR] 1.59, 95% confidence interval [CI] 1.05–2.39, p = 0.03 for 10th–15th population centile; OR 2.54, 95% CI 1.74–3.71, p < 0.001 for 5th–10th customised centile; OR 1.81, 95% CI 1.07–3.04, p = 0.03 for 30th–35th Intergrowth centile). The strength of association with adverse perinatal outcomes was different between infants below the 5th birth-weight centile for each chart (OR 4.47, 95% CI 3.30–6.04, p < 0.001 for the population chart; OR 5.78, 95% CI 4.22–7.91, p < 0.001 for the customised chart; OR 10.74, 95% CI 7.32–15.77, p < 0.001 for the Intergrowth chart) but similar in the smallest 5% of the population (OR 4.34, 95% CI 3.22–5.86, p < 0.001 for the population chart; OR 5.23, 95% CI 3.85–7.11, p < 0.001 for the customised chart; OR 4.69, 95% CI 3.47–6.34, p < 0.001 for the Intergrowth chart). For a fixed FPR of 10%, different thresholds for each chart achieved similar sensitivity for perinatal mortality in small infants (29% for all charts). Similar behaviour of different thresholds and similar risk/sensitivity for fixed FPR were observed in relation to other outcomes and for LGA infants. Limitations of this study include the relative homogeneity of the Swedish population, which limits generalisability to other populations; customised centiles may perform differently in populations with increased heterogeneity of ethnic background.ConclusionsThe risk of adverse outcomes was consistent across prop...

The pitfalls of using birthweight centile charts to audit care

“…A possible solution is to use a prescriptive birthweight standard, such as those produced by INTERGROWTH-21 st , to audit care. However our findings, and those of others [21][22][23][24][25], give reason to be cautious of this approach too. We found that the normative INTERGROWTH-21 st birthweight distribution is left-shifted compared to Australian population centiles, yielding a much lower proportion of babies with birthweight <3 rd and <10 th centile.…”

Swedish intrauterine growth reference ranges of biometric measurements of fetal head, abdomen and femur

“…During the last decade, several international growth standards have been created 5 – 8 . However, doubts have been raised regarding the applicability of these international standards when evaluated in different populations 7 , 9 – 11 . It has therefore been advised that the international standards should be evaluated in each separate population before taken into general practice 5 .…”

Gestational age and the risk of autism spectrum disorder in Sweden, Finland, and Norway: A cohort study

“…Birth year was categorized as 1995–1999, 2000–2004, 2005–2009, 2010–2014, and 2015–2016 and maternal age at birth was categorized as <20, 20–24, 25–29, 30–34, 35–39, and ≥40 years [ 35 ]. To adjust for differences in birth weight, sex-specific size for GA was calculated as “small for GA” (below or equal to the 10th percentile), “appropriate for GA” (between the 11th and 90th percentile), and “large for GA” (above the 90th percentile) [ 36 ]. Sex-specific percentiles for each gestational week were calculated within each country, using the observed birth weights as the reference.…”

“…RR of ASD increased by GA, from 40 to 24 weeks and from 40 to 44 weeks of gestation. The RR of ASD in children born in weeks [22][23][24][25][26][27][28][29][30][31][32][33][34][35][36], and 43-44 compared to weeks 37-42 were estimated at 2.31 (95% confidence interval [CI] 2.15-2.48; 1.67% vs 0.83%; p-value < 0.001), 1.35 (95% CI 1.30-1.40; 1.08% vs 0.83%; p-value < 0.001), and 1.37 (95% CI 1.21-1.54; 1.74% vs 0.83%; p-value < 0.001), respectively. The main limitation of this study is the lack of data on potential causes of pre-or postterm birth.…”