Optimal birth weight percentile cut‐offs in defining small‐ or large‐for‐gestational‐age

Aims: It remains questionable what birth weight for gestational age percentile cut‐offs should be used in defining clinically important poor or excessive foetal growth. We aimed to evaluate the optimal birth weight percentile cut‐offs for defining small‐ or large‐for‐gestational‐age (SGA or LGA). Methods: In a birth cohort‐based analysis of 17 979 120 non‐malformation singleton live births, U.S. 1995–2001, we assessed the optimal birth weight percentile cut‐offs for defining SGA and LGA. The 25th–75th percentile group served as the reference. Primary outcomes are the risk ratios (RR) of neonatal death and low 5‐min Apgar score (<4) comparing SGA or LGA versus the reference group. More than 2‐fold risk elevations were considered clinically significant. Results: The 15th birth weight cut‐off already identified SGA infants at more than 2‐fold risk of neonatal death at pre‐term, term or post‐term, except for extremely pre‐term births <28 weeks (continuous risk reductions over increasing birth weight percentiles). LGA was associated with a reduced risk of low 5‐min Apgar score at pre‐term, but an elevated risk at term and post‐term. The 97th cut‐off identified LGA infants at 2‐fold risk of low 5‐min Apgar at term. Conclusion: The commonly used 10th and 90th birth weight percentile cut‐offs for defining SGA and LGA respectively seem largely arbitrary. The 15th and 97th percentiles may be the optimal cut‐offs to define SGA and LGA respectively.     

Maternal selenium,copper and zinc concentrations in pregnancy associated with small‐for‐gestational‐age infants

Pregnancy during adolescence increases the risk of adverse pregnancy outcome, especially small‐for‐gestational‐age (SGA) birth, which has been linked to micronutrient deficiencies. Smoking has been shown to be related to lower micronutrient concentrations. Different ethnicities have not been examined. We used a subset from a prospective observational study, the About Teenage Eating study consisting of 126 pregnant adolescents (14–18‐year‐olds) between 28 and 32 weeks gestation. Micronutrient status was assessed by inductively coupled mass spectrometry. Smoking was assessed by self‐report and plasma cotinine, and SGA was defined as infants born <10th corrected birthweight centile. The main outcome measures were as follows: (1) maternal plasma selenium, copper and zinc concentrations in adolescent mothers giving birth to SGA vs. appropriate‐for‐gestational‐age (AGA) infants; and (2) comparison of micronutrient concentrations between women of different ethnicities and smoking habits. The plasma selenium {mean ± standard deviation (SD) [95% confidence interval (CI)]} concentration was lower in the SGA [n = 19: 49.4 ± 7.3 (CI: 45.9, 52.9) µg L^?1] compared with the AGA [n = 107: 65.1 ± 12.5 (CI: 62.7, 67.5) µg L^?1; P < 0.0001] group. Smoking mothers had a lower selenium concentration compared with non‐smokers (P = 0.01) and Afro‐Caribbean women had higher selenium concentrations compared with White Europeans (P = 0.02). Neither copper nor zinc concentrations varied between groups. Low plasma selenium concentration in adolescent mothers could contribute to the risk of delivering an SGA infant, possibly through lowering placental antioxidant defence, thus directly affecting fetal growth. Differences in plasma selenium between ethnicities may relate to variation in nutritional intake, requiring further investigation.     

A case–control study to examine the association between breastfeeding during late pregnancy and risk of a small‐for‐gestational‐age birth in Lima,Peru

Excessive demands on maternal nutritional status may be a risk factor for poor birth outcomes. This study examined the association between breastfeeding during late pregnancy (≥28 weeks) and the risk of having a small‐for‐gestational‐age (SGA) newborn, using a matched case–control design (78 SGA cases: birthweight <10th percentile for gestational age; 150 non‐SGA controls: 50th percentile <birthweight <90th percentile for gestational age). Between March 2006 and April 2007, project midwives visited daily three government hospitals in Lima, Peru and identified cases and matched controls based on hospital, gestational age, and inter‐gestational period. Mothers were interviewed and clinical chart extractions were completed. Factors associated with risk of SGA were assessed by their adjusted odds ratios (aOR) from conditional logistic regression. Exposure to an overlap of breastfeeding during late pregnancy was not associated with an increased risk of having a SGA newborn [aOR = 0.58, 95% confidence interval (CI): 0.10–3.30]. However, increased risk was associated with having a previous low‐birthweight birth (aOR = 6.53; 95% CI: 1.43–29.70) and a low intake of animal source foods (<25th percentile; aOR = 2.26; 95% CI: 1.01–5.04), and tended to be associated with being short (<150 cm; aOR = 2.05; 95% CI: 0.92–4.54). This study found no evidence to support the hypothesis that breastfeeding during late pregnancy increases the risk for SGA; however, studies with greater statistical power are needed to definitively examine this possible association and clarify whether there are other risks to the new baby, the toddler and the pregnant woman.     

Systematic review indicates postnatal growth in term infants born small‐for‐gestational‐age being associated with later neurocognitive and metabolic outcomes

We systematically reviewed papers published in English between 1994 and October 2015 on how postnatal weight gain and growth affect neurodevelopment and metabolic outcomes in term‐born small‐for‐gestational‐age (SGA) infants. Two randomised trials reported that enriched infant formulas that promoted early growth also increased fat mass, lean mass and blood pressure (BP), but had no effect on early neurocognitive outcomes. Meanwhile, 31 observational studies reported consistent positive associations between postnatal weight gain and growth with neurocognitive outcomes, adiposity, insulin resistance and BP. Conclusion: Few intervention studies exist, despite consistent positive associations between early growth and neurocognition in term‐born SGA infants.     

Urinary β2‐microglobulin and bronchopulmonary dysplasia: Trends in preterm infants

Background

The developmental process of bronchopulmonary dysplasia (BPD) is not identical between very preterm infants born small for gestational age (SGA) and those born appropriate for gestational age (AGA). In this study, we compared the pattern of the inflammatory response in infants of each group, by measuring urinary β2‐microglobulin (Uβ2M) as an alternative, concise, and less‐invasive biomarker.

Methods

Uβ2M and clinical details were examined at birth and at 4 weeks of age in 146 very preterm infants.

Results

Of the 57 infants diagnosed with BPD, 18 were SGA, and 39 were AGA. Uβ2M at birth was significantly lower in SGA BPD infants than in AGA BPD infants, but it increased with time. The prevalence of chorioamnionitis (CAM) was significantly lower in SGA BPD infants than in AGA BPD infants, while that of pregnancy‐induced hypertension was the opposite.

Conclusions

Exposure to prenatal factors other than CAM may sensitize fetal lungs to become vulnerable to postnatal inflammation in very preterm SGA infants with BPD.     

Refeeding syndrome in a small‐for‐dates micro‐preemie receiving early parenteral nutrition

This report describes a small‐for‐date extremely low birth weight infant who manifested bradycardic events, respiratory failure, and hemolytic jaundice during her first week of life. These complications were attributed to severe hypophosphatemia and hypokalemia. Inadequate supply and refeeding syndrome triggered by early aggressive parenteral nutrition were responsible for electrolyte abnormalities.     

A study of serum zinc levels in cord blood of neonates and their mothers

Serum zinc was estimated in the cord blood of 60 neonates of different gestational age and birth weight, and their mothers. Mean serum zinc levels in neonates FTGA, PTAGA and term SGA were 128.88±14.37, 94.32±17.79 and 111.8±9.2 ug/dl respectively. The maternal serum zinc levels in corresponding groups was 96.28±19.48, 115.44±15.41 and 93.8±7.62 ug/dl. Thus mean serum zinc level in cord blood of FT AGA newborns was significantly higher than that in PT AGA and FT SGA. Mean serum zinc level in mothers of FT AGA was significantly lower than that in mothers of PT AGA. However, there was no significant difference between the maternal serum zinc levels of FT AGA and FT SGAs. There was positive correlation between gestational age and serum zinc level in cord blood of AGAs while correlation was negative in case of their mothers. There was positive correlation between weight (keeping gestational age constant) and serum zinc level in case of neonates while corresponding maternal zinc levels did not vary. (FT AGA and FT SGA).     

Low‐birthweight rates higher among Bangladeshi neonates measured during active birth surveillance compared to national survey data

Birth size is an important gauge of fetal and neonatal health. Birth size measurements were collected within 72 h of life for 16 290 live born, singleton infants in rural Bangladesh from 2004 to 2007. Gestational age was calculated based on the date of last menstrual period. Newborns were classified as small‐for‐gestational age (SGA) based on a birthweight below the 10th percentile for gestational age, using three sets of US reference data. Birth size distributions were explored based on raw values as well as after z‐score standardisation in reference to World Health Organization (WHO) 2006 growth standards. Mean (SD) birthweight (g), length (cm) and head circumference (cm) measurements, completed within [median (25th, 75th percentile)] 15 (8, 23) h of life, were 2433 (425), 46.4 (2.4) and 32.4 (1.6), respectively. Twenty‐two per cent were born preterm. Over one‐half (55.3%) of infants were born low birthweight; 46.6%, 37.0% and 33.6% had a weight, length and head circumference below ?2 z‐scores of the WHO growth standard at birth; and 70.9%, 72.2% and 59.8% were SGA for weight based on Alexander et al., Oken et al. and Olsen et al. references, respectively. Infants in this typical rural Bangladesh setting were commonly born small, reflecting a high burden of fetal growth restriction and preterm birth. Our findings, produced by active birth surveillance, suggest that low birthweight is far more common than suggested by cross‐sectional survey estimates. Interventions that improve fetal growth during pregnancy may have the largest impact on reducing SGA rates.