The significance of contact with microbes in early life for subsequent health has been the subject of intense research during the last 2 decades. Disturbances in the establishment of the indigenous intestinal microbiome caused by cesarean section delivery or antibiotic exposure in early life have been linked to the risk of immune-mediated and inflammatory conditions such as atopic disorders, inflammatory bowel disease and obesity later in life. Distinct microbial populations have recently been discovered at maternal sites including the amniotic cavity and breast milk, as well as meconium, which have previously been thought to be sterile. Our understanding of the impact of fetal microbial contact on health outcomes is still rudimentary. Breast milk is known to modulate immune and metabolic programming. The breast milk microbiome is hypothesized to guide infant gut colonization and is affected by maternal health status and mode of delivery. Immunomodulatory factors in breast milk interact with the maternal and infant gut microbiome and may mediate some of the health benefits associated with breastfeeding. The intimate connection between the mother and the fetus or the infant is a potential target for microbial therapeutic interventions aiming to support healthy microbial contact and protect against disease.

The rise in the occurrence of obesity to epidemic proportions has made it a global concern. Great difficulty has been experienced in efforts to control this growing problem with lifestyle interventions. Thus, attention has been directed to understanding the events of one of the most critical periods of development, perinatal life. Early life adversity driven by maternal obesity has been associated with an increased risk of metabolic disease and obesity in the offspring later in life. Although a mechanistic link explaining the relationship between maternal and offspring obesity is still under investigation, the gut microbiota has come forth as a new factor that may play a role modulating metabolic function of both the mother and the offspring. Emerging evidence suggests that the gut microbiota plays a much larger role in mediating the risk of developing non-communicable disease, including obesity and metabolic dysfunction in adulthood. With the observation that the early life colonization of the neonatal and postnatal gut is mediated by the perinatal environment, the number of studies investigating early life gut microbial establishment continues to grow. This paper will review early life gut colonization in experimental animal models, concentrating on the role of the early life environment in offspring gut colonization and the ability of the gut microbiota to dictate risk of disease later in life.

Maternal and childhood obesity in pregnancy are worrisome public health issues facing our world today. New gene sequencing methods have advanced our knowledge of the disruptive effect of birth interventions and postnatal exposures on the maturation of gut microbiota and immunity during infancy. Yet, little is known about the impact of maternal pregnancy overweight on gut microbes and related processes, and how this may affect overweight risk in offspring. To address this gap in knowledge, we surveyed human studies for evidence in children, infants and pregnant women to piece together the limited literature and generate hypotheses for future investigation. From this literature, we learned that higher Lactobacillus yet lower Bacteroides spp. colonization of gut microbiota within 3 months of birth predicted risk for infant and child overweight. The abundance of bifidobacteria and staphylococci also appeared to play a role in the association with overweight, as did infant fecal immunoglobulin A levels, glycoproteins of the gut immune system that are acquired from breast milk and produced by the infant. We proposed that pregnancy overweight influences the compositional structure of gut microbiota in infants through vertical transfer of microbiota and/or their metabolites during pregnancy, delivery and breastfeeding. Finally, we brought forward emerging evidence on sex dimorphism, as well as ethnic and geographic variation, in reported associations between maternal overweight-induced gut microbiota dysbiosis and overweight risk.

The gastrointestinal tract (GIT) microbiota has been identified as an important reservoir of antibiotic resistance genes (ARGs) that can be horizontally transferred to pathogenic species. Maternal GIT microbes can be transmitted to the offspring, and recent work indicates that such transfer starts before birth. We have used culture-independent genetic screenings to explore whether ARGs are already present in the meconium accumulated in the GIT during fetal life and in feces of 1-week-old infants. We have analyzed resistance to β-lactam antibiotics (BLr) and tetracycline (Tcr), screening for a variety of genes conferring each. To evaluate whether ARGs could have been inherited by maternal transmission, we have screened perinatal fecal samples of the 1-week-old babies’ mothers, as well as a mother–infant series including meconium, fecal samples collected through the infant’s 1st year, maternal fecal samples and colostrum. Our results reveal a high prevalence of BLr and Tcr in both meconium and early fecal samples, implying that the GIT resistance reservoir starts to accumulate even before birth. We show that ARGs present in the mother may reach the meconium and colostrum and establish in the infant GIT, but also that some ARGs were likely acquired from other sources. Alarmingly, we identified in both meconium and 1-week-olds’ samples a particularly elevated prevalence of mecA (>45%), six-fold higher than that detected in the mothers. The mecA gene confers BLr to methicillin-resistant Staphylococcus aureus, and although its detection does not imply the presence of this pathogen, it does implicate the young infant’s GIT as a noteworthy reservoir of this gene.

Early patterns of gut colonization may predispose children to adult disease. Exposures in utero and during delivery are associated with the infant gut microbiome. Although ~35% of women carry group B strep (GBS; Streptococcus agalactiae) during pregnancy, it is unknown if GBS presence influences the infant gut microbiome. As part of a population-based, general risk birth cohort, stool specimens were collected from infant’s diapers at research visits conducted at ~1 and 6 months of age. Using the Illumina MiSeq (San Diego, CA) platform, the V4 region of the bacterial 16S rRNA gene was sequenced. Infant gut bacterial community compositional differences by maternal GBS status were evaluated using permutational multivariate analysis of variance. Individual operational taxonomic units (OTUs) were tested using a zero-inflated negative binomial model. Data on maternal GBS and infant gut microbiota from either 1 (n=112) or 6-month-old stool (n=150) specimens was available on 262 maternal-child pairs. Eighty women (30.5%) were GBS+, of who 58 (72.5%) were given intrapartum antibiotics. After adjusting for maternal race, prenatal antifungal use and intrapartum antibiotics, maternal GBS status was statistically significantly associated with gut bacterial composition in the 6 month visit specimen (Canberra R2=0.008, P=0.008; Unweighted UniFrac R2=0.010, P=0.011). Individual OTU tests revealed that infants of GBS+ mothers were significantly enriched for specific members of the Clostridiaceae, Ruminococcoceae, and Enterococcaceae in the 6 month specimens compared with infants of GBS- mothers. Whether these taxonomic differences in infant gut microbiota at 6 months lead to differential predisposition for adult disease requires additional study.

Breast milk constitutes one of the most important sources of postnatal microbes. However, the influence of perinatal factors on the milk microbiome is still poorly understood. The aim of our study was to assess the impact of mode of delivery on the microbiome composition and diversity present in breast milk of healthy mothers. Mature milk samples (n=10) were taken from mothers after 1 month of exclusively breastfeeding. Microbiomes from milk samples were analyzed with 16S ribosomal RNA gene pyrosequencing and targeted quantitative polymerase chain reaction (PCR). Despite inter-individual variability in bacterial composition, The Principal Coordinates Analysis clearly separated milk microbiome from mothers with vaginal delivery (n=6) from those who undergo C-section (n=4). In addition, higher bacterial diversity and richness was found in milk samples from vaginal deliveries. Quantitative PCR data showed that higher levels of Bifidobacterium spp. were related significantly to lower levels of Staphylococcus spp. Despite the low sample size, our data suggest that mode of delivery has an important impact on milk microbiome composition. Further studies with larger sample sizes are needed to confirm these results and to understand the biological effects of C-section associated microbes on infant’s health.

Immunoglobulin A (IgA) is a predominant immunoglobulin present in human breast milk and is known to play an important role in infant gut immunity maturation. Breast milk composition varies between populations, but the environmental and maternal factors responsible for these variations are still unclear. We examined the relationship between different exposures and levels of IgA in colostrum. The objective of this study was to examine whether exposures analysed influence levels of IgA in colostrum. The present study used 294 colostrum samples from the MecMilk International cohort, collected from women residing in London, Moscow and Verona. Samples were analysed in automated Abbott Architect Analyser. We found an inverse correlation between time postpartum and colostrum total IgA level (r=−0.49, P<0.001). Adjusting for maternal parity, smoking, fresh fruit and fish consumption and allergen sensitization, multiple regression model showed that IgA levels were influenced by colostrum collection time (P<0.0001) and country of collection (P<0.01). Mode of delivery influence did not appear to be significant in univariate comparisons, once adjusted for the above maternal characteristics it showed a significant influence on total IgA (P=0.01). We conclude that the concentration of IgA in colostrum drops rapidly after birth and future studies should always consider this factor in analysis. IgA concentration varied significantly between countries, with the highest level detected in Moscow and lowest in Verona. Mode of delivery effect should be confirmed on larger cohorts. Further work is needed to determine ways to correct for IgA decline over time in colostrum, and to find the cause of variations in IgA levels between the countries.

Secretory immunoglobulin A (IgA) plays a critical role in gut mucosal immune defense. Initially provided by breastmilk, IgA production by the infant gut is gradually stimulated by developing gut microbiota. This study reports associations between infant fecal IgA concentrations 4 months after birth, breastfeeding status and other pre/postnatal exposures in 47 infants in the Canadian Healthy Infant Longitudinal Development cohort. Breastfed infants and first-born infants had higher median fecal IgA concentrations (23.11 v. 9.34 µg/g protein, P<0.01 and 22.19 v. 8.23 µg/g protein, P=0.04). IgA levels increased successively with exclusivity of breastfeeding (β-coefficient, 0.37, P<0.05). This statistical association was independent of maternal parity and household pets. In the absence of breastfeeding, female sex and pet exposure elevated fecal IgA to levels found in breastfed infants. In addition to breastfeeding, infant fecal IgA associations with pre/postnatal exposures may affect gut immunity and risk of allergic disease.

Prenatal development is highly plastic and readily influenced by the environment. Adverse conditions have been shown to alter organ development and predispose offspring to chronic diseases, including diabetes and hypertension. Notably, it appears that the changes in glucocorticoid hormones or glucocorticoid receptor (GR) levels in peripheral tissues could play a role in the development of chronic diseases. We have previously demonstrated that in vitro fertilization (IVF) and preimplantation embryo culture is associated with growth alterations and glucose intolerance in mice. However, it is unknown if GR signaling is affected in adult IVF offspring. Here we show that GR expression is increased in inbred (C57Bl6/J) and outbred (CF-1× B6D2F1/J) blastocysts following in vitro culture and elevated levels are also present in the adipose tissue of adult male mice. Importantly, genes involved in lipolysis and triglyceride synthesis and responsive to GR were also increased in adipose tissue, indicating that increased GR activates downstream gene pathways. The promoter region of GR, previously reported to be epigenetically modified by perinatal manipulation, showed no changes in DNA methylation status. Our findings demonstrate that IVF results in a long-term change in GR gene expression in a sex- and tissue-specific manner. These changes in adipose tissues may well contribute to the metabolic phenotype in mice conceived by IVF.

The maternal weight gain chart proposed by Rosso and Mardones (RM) was subsequently modified by Atalah et al. (AEA). Both charts are widely used in Latin America. The purpose of this study was to compare birth length (BL) and birth weight (BW) outcomes of both charts. A prospective study of pregnant women and their offspring’s was performed in Santiago, Chile. From a total sample of 27,613 pregnant women a sub-sample of 11,465 term healthy singleton pregnant women was selected for additional analyses. κ statistics was used to study the degree of agreement of both charts in the diagnosis of maternal nutritional status. Obese and underweight women were classified using both standards at the beginning of pregnancy and compared in terms of BL<50 cm, BW<3000 g and BW>4250 g proportions. Sensitivity and specificity values of at risk newborns, whose categories were considered as gold standard, were obtained for obese and underweight women of each chart. There was a moderate agreement in the nutritional classification of these charts. Proportions of BL<50 cm and both BW<3000 g and>4250 g were similar at each nutritional category; however, absolute figures for at risk newborns were much higher in the RM underweight and obese women. The RM chart showed higher sensitivity values than the AEA chart. The higher sensitivity of the RM chart would support its use for prevention purposes. This chart is advisable for Latin American countries and also for most developing countries.

Intrauterine growth restriction (IUGR) is associated with a reduction in the numbers of nephrons in neonates, which increases the risk of hypertension. Our previous study showed that ouabain protects the development of the embryonic kidney during IUGR. To explore this molecular mechanism, IUGR rats were induced by protein and calorie restriction throughout pregnancy, and ouabain was delivered using a mini osmotic pump. RNA sequencing technology was used to identify the differentially expressed genes (DEGs) of the embryonic kidneys. DEGs were submitted to the Database for Annotation and Visualization and Integrated Discovery, and gene ontology enrichment analysis and Kyoto Encyclopedia of Genes and Genomes (KEGG) pathway analysis were conducted. Maternal malnutrition significantly reduced fetal weight, but ouabain treatment had no significant effect on body weight. A total of 322 (177 upregulated and 145 downregulated) DEGs were detected between control and the IUGR group. Meanwhile, 318 DEGs were found to be differentially expressed (180 increased and 138 decreased) between the IUGR group and the ouabain-treated group. KEGG pathway analysis indicated that maternal undernutrition mainly disrupts the complement and coagulation cascades and the calcium signaling pathway, which could be protected by ouabain treatment. Taken together, these two biological pathways may play an important role in nephrogenesis, indicating potential novel therapeutic targets against the unfavorable effects of IUGR.

There is no satisfactory explanation as to why some nephrotic syndrome (NS) patients respond to glucocorticoids and others do not. The aim of this study was to investigate an association between single nucleotide polymorphism of the MIF gene -rs755622 and serum MIF concentrations in NS patients. During a period between November 2011 and September 2012, 120 consecutive children divided into three groups [healthy children, steroid-resistant nephrotic syndrome (SRNS) and steroid-sensitive nephrotic syndrome (SSNS)] were examined. Children were defined as healthy when they had a normal estimated glomerular filtration rate and spot urinary albumin creatinine ratio <150 μg/mg creatinine. SRNS was diagnosed in children who did not respond to the usual doses of steroids within 4 weeks of initiating treatment. SSNS patients were defined as those who had remission after usual doses of steroids. The genotype of -173 G to C polymorphism of the MIF gene was determined using polymerase chain reaction restriction fragment length polymorphism methods. Serum MIF concentration was measured using sandwich enzyme-linked immunosorbent assay. The allele frequency of the C allele was higher in SRNS compared with that of SSNS patients (P=0.025). There was a trend toward an association between genotypes and serum MIF disturbances. In conclusion, this study noted elevated circulating serum MIF levels and higher frequency of the C allele of the MIF gene in SRNS patients. The presence of the C allele implies an increased risk for steroid resistance.

Earlier research suggests that maternal pelvic size is associated with offspring’s stroke risk in later life. We followed 6362 men and women from Uppsala, Sweden, born between 1915 and 1929 from 1964 to 2008 to assess whether maternal pelvic size was associated with incidence of thrombotic stroke (TS), haemorrhagic stroke (HS) and other stroke (OS). Offspring whose mothers had a flat pelvis had lower birth weight and birth-weight-for-gestational-age compared with those who did not. Inverse linear associations of birth-weight-for-gestational-age were observed with TS and OS. Female offspring whose mothers had a flat pelvis had increased risk of TS, but flat pelvis was not associated with other types of stroke. A smaller difference between intercristal and interspinous diameters and a smaller external conjugate diameter were independently associated with HS, whereas no pelvic measurements were associated with OS. We conclude that a smaller pelvis in women may impact the health of their offspring in adulthood.

Fortification of margarine with vitamin D was mandatory in Denmark during 1961–1985. The aim of the study was to assess whether gestational and early infancy exposure to margarine fortification was associated with seasonality of birth in Danish type 1 diabetes (T1D) patients. The risks of T1D in Danes born during various exposure periods around margarine fortification termination in 1985 were analyzed. As expected, the T1D hazards in males unexposed to margarine fortification and born in spring were higher than in males born in autumn: relevant hazard ratios (95% confidence intervals) in various exposure groups ranged from 1.74 (1.112/2.708) to 37.43 (1.804/776.558). There were no indications of seasonality of birth in males exposed to fortification, nor in both exposed and unexposed females. The study suggests that early life exposure to low-dose vitamin D from fortified food eliminates seasonality of birth in T1D male patients. Further studies are required to investigate the identified gender differences.