Effects of size at birth on health, growth and developmental outcomes in children up to age 18: an umbrella review

BACKGROUND

Size at birth, an indicator of intrauterine growth, has been studied extensively in relation to subsequent health, growth and developmental outcomes. Our umbrella review synthesises evidence from systematic reviews and meta-analyses on the effects of size at birth on subsequent health, growth and development in children and adolescents up to age 18, and identifies gaps.

METHODS

We searched five databases from inception to mid-July 2021 to identify eligible systematic reviews and meta-analyses. For each meta-analysis, we extracted data on the exposures and outcomes measured and the strength of the association.

FINDINGS

We screened 16 641 articles and identified 302 systematic reviews. The literature operationalised size at birth (birth weight and/or gestation) in 12 ways. There were 1041 meta-analyses of associations between size at birth and 67 outcomes. Thirteen outcomes had no meta-analysis.Small size at birth was examined for 50 outcomes and was associated with over half of these (32 of 50); continuous/post-term/large size at birth was examined for 35 outcomes and was consistently associated with 11 of the 35 outcomes. Seventy-three meta-analyses (in 11 reviews) compared risks by size for gestational age (GA), stratified by preterm and term. Prematurity mechanisms were the key aetiologies linked to mortality and cognitive development, while intrauterine growth restriction (IUGR), manifesting as small for GA, was primarily linked to underweight and stunting.

INTERPRETATION

Future reviews should use methodologically sound comparators to further understand aetiological mechanisms linking IUGR and prematurity to subsequent outcomes. Future research should focus on understudied exposures (large size at birth and size at birth stratified by gestation), gaps in outcomes (specifically those without reviews or meta-analysis and stratified by age group of children) and neglected populations.

PROSPERO REGISTRATION NUMBER

CRD42021268843.

Influence of birth-related maternal and neonatal factors on the levels of energy metabolism mediators in infants born at 32 or fewer weeks of gestation

BACKGROUND

Energy metabolism mediators, which include the adipokines (leptin, adiponectin, ghrelin) and insulin-like growth factor 1 [IGF-1], are hormone-like proteins, produced and expressed in the placenta and fetal membranes, with properties featuring metabolic adaptation and inflammatory processes. Due to the complexity of the metabolic adaptation of preterm neonates during the transition to extrauterine life, it becomes essential to recognize the factors that influence the alteration of the adipokines and IGF-1 levels in the early postpartum stage.This study assessed the significance of maternal-fetal-neonatal factors in predicting the levels of leptin, adiponectin, ghrelin, and IGF-1 in preterm infants born at 32 or fewer weeks of gestation, during the early stage of postnatal adaptation.

METHODS

Energy metabolism mediator levels were measured in urine samples obtained from extremely (less than 28 weeks) and very (28-32 weeks) preterm infants, within 48 h after their birth, and before the initiation of enteral nutrition. The urine samples were analyzed using enzyme-linked immunosorbent assay (ELISA) kits. The collected data included all birth-related maternal and neonatal factors such as maternal age, race/ethnicity, hypertensive disorders of pregnancy, diabetes, gravidity, parity, type of pregnancy, mode of delivery, and antenatal use of corticosteroids, antibiotics, magnesium sulfate, Apgar scores at 1 and 5 min, gestational age, and birth weight. We investigated the correlation between the levels of the tested mediators, the significance of the differences in their average levels based on the dichotomized maternal and neonatal factors, and the effect of the selected factors, in multiple regression models. Data from the regression models constructed for leptin, adiponectin, ghrelin, and IGF-1 are presented as regression coefficient β with Standard Error (SE) of β, coefficient of determination (R2), and adjusted R2. Before including the factor in regression models, we tested for the multicollinearity effect. Two-sided P values <0.05 were considered statistically significant.

RESULTS

Among the 70 studied infants, 47.1% were male, 40.6% were white, 28.6% were extremely preterm, and 18.6% were born with a weight <750 grams. Except for a mild interplay between the adiponectin and IGF-1 levels, there was no correlation between the levels of the other studied mediators. Up to 20% variation in the tested energy metabolism mediator levels was dependent on some of the birth-related maternal and neonatal characteristics. For instance, leptin levels were reduced in association with male gender (-0.493 [0.190], p < 0.02) and increased in infants born to primigravids (0.562 [0.215], p < 0.02). Adiponectin levels were increased in infants born to nulliparous as compared to multiparous women (0.400 [0.171], p < 0.03). Ghrelin levels were reduced in males (-0.057 [0.026], p < 0.04). IGF-1 levels were increased in the urine of extremely preterm neonates (0.357 [0.111], p < 0.01) and preterm infants born with an Apgar less than three at 1 min (0. 340 [p < 0.153], p < 0.04).

CONCLUSIONS

Nearly one-fifth of the variation in the urinary levels of the adipokines (leptin, adiponectin, ghrelin) and IGF-1 during the early postnatal stage in infants born at 32 or fewer weeks of gestation was predicated on one or more of the maternal and neonatal factors such as the infant's sex, extreme preterm gestation, a low Apgar score at 1 min, or birth to nulliparous women or primigravida mothers. Further studies will be required to explain the role of energy metabolism mediators in the postnatal adaptation of preterm-born infants.

Serum levels and gestational curve of adiponectin and leptin during adolescent pregnancy

OBJECTIVE

This study aimed to develop a curve of weekly serum levels of adiponectin and leptin among pregnant adolescents. In addition, pregestational body mass index and weight gain were assessed and correlated with the serum concentration of these molecules.

METHODS

This was a prospective cohort study, including only pregnant adolescents with eutrophic pre-gestational body mass index who were weekly followed during the evolution of gestation. The serum concentrations of adipokines were determined using commercial ELISA kits and were correlated to pre-gestational body mass index and pregnancy weight gain. A total of 157 pregnant women participated in this study.

RESULTS

Adiponectin levels showed a significant decrease among the trimesters (p=0.0004). However, we did not observe significant differences among its levels when compared weekly, neither of which was between adiponectin concentration and pre-gestational body mass index or weight gain (p=0.36 and p=0.10, respectively). In contrast, we detected a significant increase in weekly serum leptin levels (p<0.0001), positively correlated to both pre-gestational body mass index and weight gain (p=0.003 and p=0.0007, respectively).

CONCLUSION

These adipokines present a different profile throughout adolescent pregnancy.

Cord blood adiponectin and leptin are associated with a lower risk of stunting during infancy

Undernutrition is responsible for up to 45% of deaths in children under five, with low- and middle-income countries disproportionately affected. Adipokines are known modulators of metabolism and have been linked to growth rates and neurocognition during infancy. We examined the relationship(s) between cord blood adiponectin and leptin and both longitudinal growth and cognition during the first year of life using generalized estimating equations. Infants were classified as underweight (weight-for-age z-score [WAZ]), stunted (height-for-age z-score [HAZ]) or wasted (weight-for-height z-score [WHZ]) using WHOAnthro software. Cord blood adiponectin and leptin levels were highly correlated (r = 0.35, P < 0.0001) and positively associated with birth WAZ (r = 0.34 and r = 0.45, P < 0.0001, respectively). Adipokines were independently, inversely associated with weight gain. Infants in the highest quintile of adipokine production had a lower risk of being stunted, while neither was associated with lower WAZ or WHZ in final adjusted models. Cognition was not found to be independently related to cord blood leptin or adiponectin. The negative association with adipokines and rate of weight gain during infancy may reflect heightened nutritional status at birth rather than a direct hormonal influence. The relationship between leptin or adiponectin and longitudinal length gains suggests that both adipokines may promote linear growth during infancy.

Association of high maternal blood alpha-fetoprotein level with risk of delivering small for gestational age: a meta-analysis

BACKGROUND

Early identification of pregnant women at risk of delivering small-for-gestational-age (SGA) infants is required to reduce the rates of mortality and morbidity in their whole life. This meta-analysis was performed to determine whether women with higher blood alpha-fetoprotein (AFP) levels are at increased risk of SGA.

METHODS

Studies identified by searching 11 databases, including PubMed, were assessed using the Newcastle-Ottawa Scale. Subgroup and meta-regression analyses and sensitivity analysis removing a potential outlier were performed. Publication bias was assessed using Egger's test.

RESULTS

A total of 39 good-quality cohort studies involving 93,968 women and their newborn infants or fetuses ensured both internal and external validity. Relative risk of SGA among women with higher in comparison to lower blood AFP levels was 2.021 (95% CI: 1.751-2.334). Maternal blood AFP levels showed a dose-response relationship with risk of SGA. Relative risk was higher with diagnosis of SGA by ultrasound than actual birth weight (P = 0.004). Sources of heterogeneity, subgroups, confounding factors, or potential outliers did not alter the interpretations without publication bias (P = 0.320).

CONCLUSIONS

Pregnant women with higher blood AFP levels are at increased risk of SGA compared to those with lower blood AFP levels.

IMPACT

Pregnant women with higher blood alpha-fetoprotein levels (AFP) levels are at increased risk of small for gestational age (SGA) compared to those with lower blood AFP levels. High-quality evidence showed a dose-response relationship of maternal blood AFP levels with risk of delivering SGA and was robust to sources of heterogeneity, subgroups, confounding factors, potential outliers, or publication bias. Politically and practically, monitoring of maternal blood AFP level is strongly recommended to identify women at risk of delivering SGA.

Blood adiponectin concentration at birth in small for gestational age neonates: A meta-analysis

AIMS

Small for gestational age (SGA) is associated with increased rates of neonatal mortality and morbidity. Adiponectin secreted from adipose tissue is implicated in the etiology of death and illness during infancy. SGA is also a likely risk factor for the development of metabolic and clinical complications in adulthood. The present study was performed to determine whether SGA neonates and healthy controls show differences in blood adiponectin concentration at birth.

METHODS

Databases were searched to identify English-language studies providing the numbers of SGA neonates, the numbers of healthy controls, and the means and standard deviations (SDs) of blood adiponectin concentrations at birth in both groups. Study quality was assessed using the Newcastle-Ottawa Scale (NOS). A meta-analysis was performed to summarize the standardized mean differences (SMDs) in blood adiponectin concentration between SGA neonates and healthy controls.

RESULTS

The results summarized from five good quality (i.e., NOS score ≥ 5) studies involving 253 neonates showed that blood adiponectin concentration was significantly lower in SGA neonates than in healthy controls (P = 0.016), and the effect was moderate (i.e., SMD = 0.4-0.7).

CONCLUSIONS

Synthetic evidence indicated that blood adiponectin concentration at birth is lower in SGA neonates than in healthy controls.