Associations of severe adverse perinatal outcomes among continuous birth weight percentiles on different birth weight charts: a secondary analysis of a cluster randomized trial

Abstract

Objective To identify neonatal risk for severe adverse perinatal outcomes across birth weight centiles in two Dutch and one international birth weight chart. Background Growth restricted newborns have not reached their intrinsic growth potential in utero and are at risk of perinatal morbidity and mortality. There is no golden standard for the confirmation of the diagnosis of fetal growth restriction after birth. Estimated fetal weight and birth weight below the 10th percentile are generally used as proxy for growth restriction. The choice of birth weight chart influences the specific cut-off by which birth weight is defined as abnormal, thereby triggering clinical management. Ideally, this cut-off should discriminate appropriately between newborns at low and at high risk of severe adverse perinatal outcomes and consequently correctly inform clinical management. Methods This is a secondary analysis of the IUGR Risk Selection (IRIS) study. Newborns (n = 12 953) of women with a low-risk status at the start of pregnancy and that received primary antenatal care in the Netherlands were included. We examined the distribution of severe adverse perinatal outcomes across birth weight centiles for three birth weight charts (Visser, Hoftiezer and INTERGROWTH) by categorizing birth weight centile groups and comparing the prognostic performance for severe adverse perinatal outcomes. Severe adverse perinatal outcomes were defined as a composite of one or more of the following: perinatal death, Apgar score < 4 at 5 min, impaired consciousness, asphyxia, seizures, assisted ventilation, septicemia, meningitis, bronchopulmonary dysplasia, intraventricular hemorrhage, periventricular leukomalacia, or necrotizing enterocolitis. Results We found the highest rates of severe adverse perinatal outcomes among the smallest newborns (< 3rd percentile) (6.2% for the Visser reference curve, 8.6% for the Hoftiezer chart and 12.0% for the INTERGROWTH chart). Discriminative abilities of the three birth weight charts across the entire range of birth weight centiles were poor with areas under the curve ranging from 0.57 to 0.61. Sensitivity rates of the various cut-offs were also low. Conclusions The clinical utility of all three charts in identifying high risk of severe adverse perinatal outcomes is poor. There is no single cut-off that discriminates clearly between newborns at low or high risk. Trial Registration Netherlands Trial Register NTR4367. Registration date March 20th, 2014.

The clinical performance and population health impact of birthweight‐for‐gestational age indices at term gestation

“…Information on the SGA and LGA status of foetuses and infants is routinely used for improving obstetric and neonatal management. However, as previous studies have shown 14,15,23–26,38,41,42 and our study confirms, SGA or LGA diagnosis, when used in isolation without other predictors, performs poorly for predicting SNMM; in other words, the probability of SNMM is not materially changed by such a diagnosis. In our study, the expected rate of SNMM changed marginally from 20.2 per 1000 live births to 23.8, 36.1 and 54.4 per 1000 live births using a mild (10% increase in odds), moderate (50% increase) or extreme (100% increase) definition of SGA among female singletons at 39 weeks' gestation (Table 1).…”

“…Previous studies, 14,15,[23][24][25][26]38,41,42 have shown that estimated foetal weight-or birthweight-for-gestational age indices perform poorly in terms of predicting serious neonatal morbidity and perinatal mortality. These studies used receiver-operatingcharacteristics (ROC) curves and area-under-the-curve methods, which are well-accepted methods for identifying the optimal cut-point of a biomarker for discrimination/prediction.…”

Search for the best prediction model, definition and growth charts for fetal growth restriction using a composite of adverse perinatal outcomes: a catch‐22?

“…Much of current research on FGR hinges on finding the best growth chart, definition, monitoring-management strategy and prediction model for adverse outcomes. The majority of studies reporting on these issues evaluate the incidence of a composite adverse perinatal outcome (CAPO) [10][11][12][13][14] . These CAPOs have obvious face value at first glance, however, we posit that their use can also be problematic.…”

Predictive value of fetal growth trajectory from 20 weeks of gestation onwards for severe adverse perinatal outcome in low‐risk population: secondary analysis of IRIS study

“…Typically, SGA is defined as an abdominal circumference (AC), estimated fetal weight (EFW) or birth weight below the 10 th percentile (< p10). However, this approach is inherently flawed, because many SGA fetuses and newborns are constitutionally small, while some fetuses and newborns may not have reached their intrinsic growth potential despite having a weight above this cut-off 8,10,11 . Also, there is a risk of inadequate assessment of fetal size and growth due to the low sensitivity and specificity of sonographic fetal biometric measurements 7 .…”

“…However, many SGA fetuses and newborns are constitutionally small while on the other hand some fetuses and newborns with a weight above the cut-off may not have reached their intrinsic growth potential. 8,10,11 Also, there is a risk of inadequate assessment of fetal size and growth due to the low sensitivity and specificity of ultrasound fetal biometric measurements. 7 Currently, no tool exists that weighs fetal size against the unknown entity of intrinsic growth potential.…”