Intrauterine growth and postnatal fasting metabolism in infants of obese mothers

Factors that affect maternal insulin resistance and modify fetal growth and body composition

Fetal growth is multifactorial and can be altered by a variety of extrinsic and intrinsic factors. The maternal, placental, and fetal contribution to growth must all be considered. Of particular interest are maternal metabolic regulation and the availability of nutrients to the developing fetus. Weight gain, hyperlipidemia, and insulin resistance occur as a normal adaptation to pregnancy. Obesity and underlying insulin resistance among women of reproductive age are rapidly increasing, and the contribution of pregnancy on this abnormal metabolic background poses additional maternal and fetal challenges. Many components of the metabolic syndrome have been associated with changes in fetal growth, including obesity, dyslipidemia, hypertension, and insulin resistance or glucose intolerance. Additional factors affect fetal growth and include diet, exercise, and smoking. In this review, we briefly discuss the importance and descriptions of fetal growth, followed by a discussion of several of the extrinsic and intrinsic established factors affecting fetal growth. We highlight factors that may modify fetal growth and body composition directly or indirectly through alterations in maternal metabolism.

Abnormal maternal body mass index and obstetric and neonatal outcome

OBJECTIVE

The objective of this study is to examine the effects of abnormal maternal body mass index (BMI), either underweight or severe or morbid obesity (BMI >35), on obstetrical and neonatal outcomes.

METHODS

A three-year period (2.007-2.009) observational retrospective study was carried out in Granada (Spain). Women were categorized by first ten weeks of pregnancy BMI, according to World Health Organization (WHO) into three groups: underweight (<18.5), normal (20-24.9), and severe or morbid obese (>35). Obstetrical and neonatal outcomes were evaluated using normal group as reference after suitable adjustments for confounding factors.

RESULTS

3.016 patients out of 12.781 single births were included. Maternal BMI classified 168 women (5.5 %) as underweight, 2.597 (86.1%) as normal, and 251 (8.3%) as severe or morbidly obese. As compared to normal women, underweight women were younger, and class II or III obese showed higher parity and higher incidence of hypertension disorders and Diabetes Mellitus. After controlling for these confounders, underweight women showed increased adjusted risk of oligohydramnios and low birth weight babies, and severe or morbidly obese women had an increased adjusted risk of Streptococcus Group B colonization, induction of labour, elective and emergency cesarean section, fetal macrosomia, fetal acidosis at birth, and perinatal mortality.

CONCLUSIONS

Severe or morbid obesity were associated with an increased risk of adverse perinatal outcome and mortality and should be managed as high-risk pregnancies.

Larger infant size at birth reduces the negative association between maternal prepregnancy body mass index and breastfeeding duration

Women who are overweight or obese prepregnancy have shorter durations of producing milk (PM) and feeding breast milk exclusively (FBM-ex) than normal-weight women. We proposed that infant size at birth may reduce the negative associations between prepregnancy BMI and the durations of PM and FBM-ex. We used data from 2798 participants in the Infant Feeding Practices Study II and characterized infant size at birth as weight-for-gestational age (WGA). To assess possible mediation of the associations between maternal BMI and the durations of PM and FBM-ex by infant size at birth, Baron and Kenny's methods, the Sobel test, and bootstrapping were used. As expected, prepregnancy BMI was negatively associated (P < 0.0001) with the durations of PM and FBM-ex; it also was positively associated (P < 0.0001) with infant size at birth. However, infant WGA was positively associated (P < 0.0003) with the durations of PM and FBM-ex after adjustment for BMI. Thus, the negative associations between BMI and the durations of PM and FBM-ex were reduced by infant WGA; i.e. the statistical removal of infant size at birth increased the magnitude of the negative associations between BMI and the durations of PM and FBM-ex. Thus, the tendency of heavier mothers to deliver heavier infants reduces the true magnitude of the association between maternal prepregnancy BMI and shortened breastfeeding duration.

Long-term effect of maternal obesity on pancreatic beta cells of offspring: reduced beta cell adaptation to high glucose and high-fat diet challenges in adult female mouse offspring

AIM/HYPOTHESIS

Obesity is a global problem with high risks of cardiovascular diseases, stroke and type 2 diabetes. It is well known that maternal obesity affects offspring by inducing malformation, functional abnormalities in many organs and cells, and by increased risk of obesity and type 2 diabetes. However, little is known about abnormalities induced by maternal obesity in pancreatic beta cells of offspring.

METHODS

We used mouse mothers with the Agouti yellow modification on a C57BL/6 background as a maternal model of normoglycaemic obesity, and produced Agouti-negative offspring. Half of the offspring were fed a high-fat diet. Offspring glucose tolerance was tested at different ages, and animals were killed at 50 weeks of age for islet function analysis.

RESULTS

Maternal obesity impaired glucose tolerance in female offspring fed a high-fat diet, and significantly reduced insulin secretion at 50 weeks of age in female offspring that had been fed a normal diet and high-fat diet. Insulin secretion and glucose potentiation from these islets were significantly reduced. Islet protein, DNA and insulin contents were increased while glyceraldehyde-3-phosphate dehydrogenase and transketolase activities were reduced in female offspring.

CONCLUSIONS/INTERPRETATION

Our results indicate that maternal obesity has a long-term effect on the beta cells of female, but not of male, offspring, and leads to increased risk of gestational diabetes and type 2 diabetes in the offspring's later lives.

Gestational diabetes and insulin resistance: role in short- and long-term implications for mother and fetus

Gestational diabetes and obesity are the common metabolic abnormalities occurring during pregnancy. Decreased maternal pregravid insulin sensitivity (insulin resistance) coupled with an inadequate insulin response are the pathophysiological mechanisms underlying the development of gestational diabetes. Insulin-regulated carbohydrate, lipid and protein metabolism are all affected to a variable degree. Decreased maternal insulin sensitivity in women with gestational diabetes may increase nutrient availability to the fetus, possibly accounting for an increased risk of fetal overgrowth and adiposity. Epidemiological studies from Europe show an increased risk of the insulin resistance syndrome in adults who were low birth weight at delivery. However, in the United States over the past 20 y there has been a significant 33% increase in the incidence of type 2 diabetes, which has been associated with a parallel increase in obesity. All age groups have been affected but the most dramatic increases have occurred in adolescents. The relationship between decreased maternal insulin sensitivity and fetal overgrowth particularly in obese women and women with gestational diabetes may help explain the increased incidence of adolescent obesity and related glucose intolerance in the offspring of these women. In this review, we address 1) the pathophysiology of gestational diabetes, 2) the changes in maternal insulin sensitivity during pregnancy that effect maternal accretion of adipose tissue and energy expenditure, 3) the influence of maternal metabolic environment on fetal growth, 4) the life-long effect of being born at either extreme of the birth weight continuum and 5) micronutrients and decreased insulin sensitivity during pregnancy.

Obesity may impair lactogenesis II

Data from livestock species and experimental animal models suggest that excess body fatness may impair lactogenesis. For example, it has long been known that overfed dairy cows are at risk of fat cow syndrome, a condition characterized by lactation failure in the early postpartum period. Obese rats often lose their litters in the early postpartum period to primary lactation failure. A negative association between high body mass index (BMI) before conception and the duration of lactation has been documented in studies from diverse human populations. Findings from our laboratory establish that among women who ever attempted to breastfeed their infants, high BMI before conception was also associated with failure to initiate breastfeeding successfully. In a more recent study, we found that high prepregnant BMI was specifically associated with later onset of lactogenesis II. This was mediated by parity but not by breastfeeding behavior. Psychosocial factors related to a woman's intention to breastfeed and her planned duration of breastfeeding did not modify this association. Taken together, these findings in animals and women strongly suggest that maternal obesity in the perinatal period is a cause of delayed lactogenesis.

Maternal factors that determine neonatal size and body fat

These data are a review of previously published data. Initially, body composition was estimated in 186 neonates. Fat- free mass (FFM), which constituted 86% of birth weight, accounted for 83% of the variance in birth weight; fat mass (FM), which constituted 14% of birth weight, accounted for 46% of the variance in birth weight. Male neonates were an average of 175 g heavier than females. FFM was greater among males compared with females (P = 0.0001). Using stepwise logistic regression, 29% of the variance in birth weight, 30% in FFM, and 17% in FM was accounted for. Independent variables included maternal height, pregravid weight, weight gain during pregnancy, education, parity, paternal height and weight, neonatal sex, and gestational age. Including maternal insulin sensitivity explained 48% of the variance in birth weight, 53% in FFM, and 46% in FM. There was a positive correlation between weight gain and birth weight in control subjects but a negative correlation in subjects with gestational diabetes mellitus. Lastly, the roles of insulin, insulin-like growth factors, and leptin were examined in relation to fetoplacental growth and body composition. The assessment of fetal/neonatal body composition may improve the understanding of the effect of differential factors on fetal growth. Factors associated with accretion of fetal adipose tissue in late gestation are less well understood compared with birth weight and FFM. Additional studies of maternal glucose and lipid metabolism are needed to better evaluate fetal growth.

Role of the prenatal environment in the development of obesity

Establishing that prenatal life is a critical or sensitive period for the development of obesity may focus basic research and clinical prevention efforts on this period. This review summarizes evidence that the intrauterine environment influences the risk of later obesity and considers the mechanisms by which this may occur. The association between birth weight and adult weight suggests that there are enduring effects of the intrauterine environment on later obesity risk. We examine whether the maternal factors of diabetes, obesity, and pregnancy weight gain alter the intrauterine environment and thereby increase the risk of later obesity in the offspring. Of these maternal factors, evidence is strongest for the role of maternal diabetes. No single mechanism explains how these maternal factors could change the intrauterine environment to increase obesity risk. However, all potential mechanisms involve an altered transfer of metabolic substrates between mother and fetus, which may influence the developing structure or function of the organs involved in energy metabolism.

Carbohydrate metabolism in the fetus and neonate and altered neonatal glucoregulation

Altered glucose homeostasis in the neonate often results from antecedent events during fetal life. This article describes the normal and altered development of glucoregulatory capabilities during perinatal life and relates it to problems of hypo- and hyperglycemia in the neonate.