Comparative study between Fenton and intergrowth 21 charts in a sample of Lebanese premature babies

Prematurity is becoming more frequent nowadays especially with the development of artificial fertilization methods [1]. In 2016, the Center for Disease Control and Prevention (CDC) declared that around one baby out of 10 is born premature [2, 3]. Newborn’s growth is an important marker and a screening method for a number of pathologies or deficiencies [4], which needs to be tracked through growth charts. The latter would lead to a better monitoring of the nutritional status, thus, may limit the depth and duration of diet-related growth restriction and its short- and long-term damages thereafter [3].

In fact, many charts have been developed, mostly based on intrauterine growth and rarely adapted to preterm newborns. Indeed, preterm babies are not fetuses as they no longer live in-utero [ 5]. Regardless of their apparent independence, they have not acquired the growth and survival skills of full-term babies yet and present a physiological immaturity. Consequently, when assessed via common growth charts, these newborns remain under the 10th percentile for a long time and do not catch up with normal growth until the age of two to three years. For this motive, the actual trend is to supplement this population with a hypercaloric nutrition to compensate for this extra-uterine growth restriction. Despite this supplementation, most babies fail to reach their set growth goals still.

Within that scope, alarming studies have shown an association between prematurity and obesity in adulthood, with question marks raised about the link between “overfeeding” the preterm newborns, obesity and cardiovascular complications later in life [6]. In the neonatal population aged between 36 and 50 weeks of unadjusted age, the Fenton chart is considered one of the best charts for assessing longitudinal growth [7]. Nevertheless, it showed two weaknesses: it does not reflect the adaptation of the premature newborn to extra-uterine life and it under- or overestimates newborn’s growth.

The most commonly used chart at the Notre Dame des Secours University Hospital Center-Byblos (CHU-NDS), is the Fenton chart 2003, which has not been updated till now. Between 2009 and 2014, the Intergrowth21 project has emerged as a successful growth chart and underwent rigorous processes that ensured that the data collected in the INTERGROWTH-21st project is of exceptionally high quality [8]. Intergrowth-21 charts are used to create standards for postnatal growth of premature infants especially those born before 32 gestational weeks [9]. While disagreements on the Fenton charts continue, the results of the Intergrowth 21st project were awaited with great interest. The “Intergrowth 21^st Project” was a prospective multicenter, multi-ethnic study, which included low-risk women, non-smokers, with a normal pregnancy history, and no health problems that could affect fetal growth [10]. All maternal health care and nutritional needs were met. Birth and postnatal growth standards were developed from data collected from a cohort of uncomplicated pregnancies with normal growing fetuses [11]. These very strict selection criteria were mandatory, in order to create standards on how the normal growth of healthy premature babies should be.

In a recent systematic review, 61 longitudinal reference charts were identified and compared to the Intergrowth-21 chart [9]; assessments made using the Intergrowth-21 charts demonstrated a reduction in the diagnosis of extrauterine growth retardation [9, 12]. Many infants who were classified as having restricted growth according to the Fenton charts, turned out to have normal postnatal growth according to the Intergrowth-21 charts [12]. Another important point is that, like the World Health Organization (WHO) growth standards, the Intergrowth-21 growth standards aim at producing graphs that describe optimal rather than average growth, which could be used worldwide.

Being in a developing country, a local validation before adapting Intergrowth-21 charts to our new born infants is necessary, especially to avoid the misclassification of their size, which may have an impact on their nutritional support. For these reasons, the objective of this study was to check which method (the universal Fenton 2003 curves or the Intergrowth-21 curves) used in the neonatology department at CHU-NDS would predict height, weight and cranial perimeter of premature Lebanese babies better. This study would help us evaluate the difference between both curves in terms of extra- and intra-uterine growth restriction, reflected by weight, height and head circumference at birth and verify later the convergence between the intergrowth-21 and the WHO curves of the child health record book around the sixth month of life.

Out of a total of 492 medical record extracted, 318 (64.63%) newborns aged between 27 and 36 weeks of gestation met the inclusion criteria. The distribution of gestational ages showed that 52.8% of the babies were born between 34 and 36 gestational weeks, whereas the remaining newborns were under 33 gestational weeks (Fig. 1). The most frequent cause of admission to the NICU was multiple pregnancies (32.4%), followed by placental insufficiency (22%), respiratory distress of different etiologies (22%) and infections (20.1%).

The majority of the newborns (98.4%) were admitted to the NICU of the CHU-NDS from maternity ward and 1.6% were transferred before birth from another hospital. The mean age of birth was 33.26 ± 2.10 weeks of gestation. Consanguinity was present in 11.6% of the cases and caesarean section accounted for 85.8% of deliveries. Moreover, 29.9% of the babies were intubated and 78.8% received more than 2 blood transfusions during their stay; 49.7% of infants were fed by breast milk and formula milk, 48.1% by formula milk alone and 1.3% were exclusively breastfed. We note that in-vitro fertilization methods accounted for 24.8% of pregnancies.

Growth monitoring is an essential tool that reflects the overall health of neonates, especially preterm infants. It helps assess the nutritional status and detect pathological deviations. A meta-analysis, published in 2015, of 16 prospective cohorts of premature newborn comparing the 1991 US birthweight reference, the 1999–2000 US birthweight reference and the Intergrowth-21st standards, revealed a prevalent reduction of small for gestational age preterm newborn by more than a quarter, with no significant change in the risk of associated neonatal mortality [13]. Conversely, newer results from a retrospective study showed that the incidence of small for gestational age preterm newborns was higher with the Intergrowth 21st standards compared to the Fenton ones. The difference between the results of those research [12] prompted us to conduct our study. Growth curves monitor height, weight, and head circumference progression, therefore a reference chart adopting growth curves that are applicable for all ethnicities and races using anthropometric measures should be used in order to provide adequate assessment [14]. In our study, a comparison of the weight and height percentiles of the whole sample showed that before two weeks of age, Fenton growth charts showed better results compared to the Intergrowth 21; after two weeks of age, Intergrowth 21 charts showed higher R2 values for weight and height than Fenton charts.

The Fenton 2003 growth charts have been adopted in the NICU of the CHU-NDS so far in order to follow the improvement of growth in preterm neonates, especially those receiving parenteral nutrition according to the international nutritional guidelines. In most cases, these curves have shown these infants to have growth retardation despite adequate nutrition and introduction of amino acids, electrolytes and multivitamin complexes very early; consequently, those babies are exposed to intensive parenteral nutrition for a long period of time, which further delays their discharge from NICU. The main reason behind this is that Fenton growth charts assessment is based on intrauterine growth standards [15], causing the overfeeding of these newborns to lead to obesity and metabolic syndrome later in life. On another hand, the Intergrowth-21 standards aimed at producing charts that set breastfeeding as the norm to follow and described optimal rather than average growth, which could be used worldwide [ 16].

The results of our study are controversial since the Fenton growth charts showed superiority predicting newborn’s growth in terms of weight, height and cranial perimeter at birth and at 4 weeks compared to the Intergrowth-21 ones, whereas Intergrowth 21 charts showed higher percentiles for weight and height at 2 two weeks of age compared to the Fenton charts. The results obtained could have been affected by many factors, including ethnicity that could not be investigated in this study due to its retrospective aspect. Therefore, further studies that take this study’s limitations into account, are needed.