Effect of a low-glycemic-index diet during pregnancy on obstetric outcomes

Glycemic index and glycemic load of carbohydrates in the diabetes diet

Medical nutrition therapy is the first line of treatment for the prevention and management of type 2 diabetes and plays an essential part in the management of type 1 diabetes. Although traditionally advice was focused on carbohydrate quantification, it is now clear that both the amount and type of carbohydrate are important in predicting an individual's glycemic response to a meal. Diets based on carbohydrate foods that are more slowly digested, absorbed, and metabolized (i.e., low glycemic index [GI] diets) have been associated with a reduced risk of type 2 diabetes and cardiovascular disease, whereas intervention studies have shown improvements in insulin sensitivity and glycated hemoglobin concentrations in people with diabetes following a low GI diet. Research also suggests that low GI diets may assist with weight management through effects on satiety and fuel partitioning. These findings, together with the fact that there are no demonstrated negative effects of a low GI diet, suggest that the GI should be an important consideration in the dietary management and prevention of diabetes.

A systematic review on animal models of maternal high fat feeding and offspring glycaemic control

The mechanistic link between obese parents and obese offspring and the relative role of genes, and a shared environment is not completely understood. Animal models help us to differentiate between genetic and environmental factors, and the interaction between the two. However, the willingness of researchers to blend results from multiple models makes it difficult for clear mechanisms to be identified for specific hypothesis-driven research. As such we conducted a systematic review of animal models of maternal high fat feeding in an effort to identify the affect on the offspring glycaemic control. Maternal and offspring outcomes are reported in an effort to identify possible relationships to facilitate and focus on future research. We present here data from 11 studies investigating glycaemic control in offspring exposed to a high fat diet (HFD) during maternal gestation only or gestation and lactation. Studies in this review identify a real risk of type 2 diabetes and obesity in male offspring exposed to a maternal HFD. Poor glycaemic control in the offspring appears to be independent of maternal obesity, birth weight or post-weaning macronutrient intake. Inconsistencies between studies however, limit our capacity to identify mechanisms for the developmental origin of these diseases in animal models of overnutrition.

Perceived barriers to application of glycaemic index: valid concerns or lost in translation?

The term glycaemic-index (GI) originally appeared in the literature in the early 1980s. GI categorizes carbohydrate according to glycaemic effect postprandially. Since its inception, GI has obtained and maintained interest of academics and clinicians globally. Upon review of GI literature, it becomes clear that the clinical utility of GI is a source of controversy. Can and should GI be applied clinically? There are academics and clinicians on both sides of the argument. Certainly, this controversy has been a stimulus for the evolution of GI methodology and application research, but may also negatively impact clinicians' perception of GI if misunderstood. This article reviews two assessments of GI that are often listed as barriers to application; the GI concept is (1) too complex and (2) too difficult for clients to apply. The literature reviewed does not support the majority of purported barriers, but does indicate that there is a call from clinicians for more and improved GI education tools and clinician GI education. The literature indicates that the Registered Dietitian (RD) can play a key role in GI knowledge translation; from research to application. Research is warranted to assess GI education tool and knowledge needs of clinicians and the clients they serve.

Glycemic index and pregnancy: a systematic literature review

Background/Aim. Dietary glycemic index (GI) has received considerable research interest over the past 25 years although its application to pregnancy outcomes is more recent. This paper critically evaluates the current evidence regarding the effect of dietary GI on maternal and fetal nutrition. Methods. A systematic literature search using MEDLINE, EMBASE, CINAHL, Cochrane Library, SCOPUS, and ISI Web of Science, from 1980 through September 2010, was conducted. Results. Eight studies were included in the systematic review. Two interventional studies suggest that a low-GI diet can reduce the risk of large-for-gestational-age (LGA) infants in healthy pregnancies, but one epidemiological study reported an increase in small-for-gestational-age (SGA) infants. Evidence in pregnancies complicated by gestational diabetes mellitus (GDM), though limited (n = 3), consistently supports the advantages of a low-GI diet. Conclusion. There is insufficient evidence to recommend a low-GI diet during normal pregnancy. In pregnancy complicated by GDM, a low-GI diet may reduce the need for insulin without adverse effects on pregnancy outcomes. Until larger-scale intervention trials are completed, a low-GI diet should not replace the current recommended pregnancy diets from government and health agencies. Further research regarding the optimal time to start a low-GI diet for maximum protection against adverse pregnancy outcomes is warranted.

Effect of a low glycaemic index diet on blood glucose in women with gestational hyperglycaemia

AIM

The objectives of this pilot study were to determine the feasibility and effect on glycaemic control of a low-glycaemic-index (GI) diet in women with gestational diabetes or impaired glucose tolerance of pregnancy.

METHODS

participants, recruited from the Diabetes-in-Pregnancy Clinic of an inner-city teaching hospital serving a predominantly non-Caucasian population, were randomized to a low-GI (n=23) or control (n=24) diet and followed from 28 weeks gestation until delivery. Self-monitored-blood-glucose (SMBG), maternal and infant weight were collected from medical charts. Dietary intakes were assessed using diet records and questionnaires.

RESULTS

diet GI on control (58, 95% CI: 56,60) was significantly higher than on low-GI (49, 95% CI: 47,51; p=0.001). Glycaemic control improved on both diets, but more postprandial glucose values were within target on low-GI (58.4% of n=1891) than control (48.7% of n=1834; p<0.001). SMBG post-breakfast was directly related to pre-pregnancy BMI in the control, but not the low-GI group (BMI*diet interaction; p=0.021). Participants accepted the study foods and were willing to consume them post-intervention.

CONCLUSIONS

a low-GI diet was feasible and acceptable in this sample and facilitated control of postprandial glucose. A larger study is needed to determine the effect of a low-GI diet on maternal and infant outcomes.

Impact of maternal diet during pregnancy and breastfeeding on infant metabolic programming: a prospective randomized controlled study

OBJECTIVES

To evaluate the impact of maternal diet and intensive dietary counselling during pregnancy and breastfeeding on the infant's metabolic status.

SUBJECTS/METHODS

At the first trimester of pregnancy, 256 women were randomized into a control/placebo group and two dietary counselling groups (diet/probiotics and diet/placebo). The counselling, with double-blind randomization to probiotics (Lactobacillus rhamnosus GG and Bifidobacterium lactis) or placebo, targeted excessive saturated fat and low fibre consumption. Maternal diet was evaluated repeatedly during pregnancy and postpartum by means of 3 days' food diaries. Metabolic markers, serum 32-33 split and intact proinsulin, leptin/adiponectin ratio, skinfold thickness and waist circumference were measured of 194 healthy infants at the age of 6 months, and the high levels were taken to mirror adverse metabolic status.

RESULTS

The proportion of infants with a high 32-33 split proinsulin was significantly lower in dietary counselling with probiotics (n = 6/62, 9.7%) or placebo (n = 7/69, 10.1%) compared with the control/placebo group (n = 17/63, 27.0%). The high split proinsulin was associated with larger skinfold thickness, waist circumference and higher leptin/adiponectin ratio in the infants (P < 0.05). With respect to maternal diet during pregnancy, the highest and lowest tertiles of fat intake increased the infant's risk of high split proinsulin, whereas those of butter associated correspondingly with the infant's waist circumference. Further, breastfed infants showed a reduced risk of high split proinsulin and leptin/adiponectin ratio compared with formula-fed infants.

CONCLUSIONS

Modification of maternal diet during pregnancy and breastfeeding may benefit infant metabolic health. High split proinsulin reflects adverse metabolic status in infancy, which can be improved by early dietary counselling.

Effects of a low-glycemic load diet in overweight and obese pregnant women: a pilot randomized controlled trial

BACKGROUND

The optimal diet for pregnancy that is complicated by excessive weight is unknown.

OBJECTIVE

We aimed to examine the effects of a low-glycemic load (low-GL) diet in overweight and obese pregnant women.

DESIGN

We randomly assigned 46 overweight or obese pregnant women to receive a low-GL or a low-fat diet. Participants received carbohydrate-rich foods, fats, and snack foods through home delivery or study visits. The primary outcome was birth weight z score. Other endpoints included infant anthropometric measurements, gestational duration, maternal weight gain, and maternal metabolic parameters.

RESULTS

There were no significant differences in birth weight z score or other measures of infant adiposity between groups. However, in the low-GL compared with the low-fat group, gestational duration was longer (mean ± SD: 39.3 ± 1.1 compared with 37.9 ± 3.1 wk; P = 0.05) and fewer deliveries occurred at ≤ 38.0 wk (13% compared with 48%, P = 0.02; with exclusion of planned cesarean deliveries: 5% compared with 53%; P = 0.002). Adjusted head circumference was greater in the low-GL group (35.0 ± 0.8 compared with 34.2 ± 1.3 cm, P = 0.01). Women in the low-GL group had smaller increases in triglycerides [median (interquartile range): 49 (19, 70) compared with 93 (34, 129) mg/dL; P = 0.03] and total cholesterol [13 (0, 36) compared with 33 (22, 56) mg/dL, P = 0.04] and a greater decrease in C-reactive protein [-2.5 (-5.5, -0.7) compared with -0.4 (-1.4, 1.5) mg/dL, P = 0.007].

CONCLUSIONS

A low-GL diet resulted in longer pregnancy duration, greater infant head circumference, and improved maternal cardiovascular risk factors. Large-scale studies are warranted to evaluate whether dietary intervention during pregnancy aimed at lowering GL may be useful in the prevention of prematurity and other adverse maternal and infant outcomes. This trial is registered at clinicaltrials.gov as NCT00364403.

Gestational diabetes: risk factors and recent advances in its genetics and treatment

The Hyperglycemia and Adverse Pregnancy Outcome (HAPO) study of over 23000 diabetes-free pregnancies has shown that at a population level an unequivocal linear relationship exists between maternal glucose concentrations around the beginning of the third trimester of pregnancy and the risk of their baby being born above the ninetieth centile for weight. With the rising incidence of gestational diabetes (GDM) across the developed world, largely paralleling the increased prevalence of obesity, there has been a sharp increase in the risk of pregnancy complications developing related to the birth of macrosomic babies. The associated additional long-term complications of GDM pregnancies means that in the future there is likely to be a large increase in the incidence of type 2 diabetes and associated conditions in both the mothers and their affected offspring. The present review seeks to highlight recent advances and remaining gaps in knowledge about GDM in terms of its genetics (where some of the recently discovered polymorphic risk factors for type 2 diabetes have also proved to be risk factors for GDM) and its treatment by diet, exercise and drugs.

The maternal and fetal impacts of obesity and gestational diabetes on pregnancy outcome

Obesity has reached pandemic proportions and is of growing concern worldwide. Adverse health outcomes associated with a raised body mass index present the greatest challenge currently facing clinicians across all disciplines. Obesity is a chronic illness which is associated with metabolic disease, nutritional deficiency, musculoskeletal complications and cancer. These obesity-related health issues extend to pregnancy where they are responsible for producing a variety of medical and obstetric complications resulting in an increased incidence of maternal and fetal adverse outcomes. Management of diet, gestational diabetes and gestational and inter-gestational weight may improve outcomes in women who are obese during pregnancy. Specific recommendations for the management of obesity in pregnancy have recently been published.

Dietary glycemic index: health implications

Weight loss can be achieved by any means of energy restriction, but the challenge is to achieve sustainable weight loss and prevent weight "creep" without increasing the risk of chronic disease. The modest success of low fat diets has prompted research on alternative dietary strategies, including high protein diets and low glycemic index (GI) diets. Conventional high carbohydrate diets, even when based on wholegrain foods, increase postprandial glycemia and insulinemia and may compromise weight control via mechanisms related to appetite stimulation, fuel partitioning, and metabolic rate. This paper makes the case for the benefits of low glycemic index diets over higher protein diets. Both strategies are associated with lower postprandial glycemia, and both are commonly labeled as "low glycemic load," but the long-term health effects are likely to be different. A large body of evidence, which now comprises observational prospective cohort studies, randomized controlled trials, and mechanistic experiments in animal models, provides robust support for low GI carbohydrate diets in the prevention of obesity, diabetes, and cardiovascular disease. Although lower carbohydrate, higher protein diets increase the rate of weight loss, cohort studies and meta-analyses of clinical trials suggest the potential for increased mortality.

Maternal metabolism and obesity: modifiable determinants of pregnancy outcome

BACKGROUND

Obesity among pregnant women is highly prevalent worldwide and is associated in a linear manner with markedly increased risk of adverse outcome for mother and infant. Obesity in the mother may also independently confer risk of obesity to her child. The role of maternal metabolism in determining these outcomes and the potential for lifestyle modification are largely unknown.

METHODS

Relevant studies were identified by searching PubMed, the metaRegister of clinical trials and Google Scholar without limitations. Sensitive search strategies were combined with relevant medical subject headings and text words.

RESULTS

Maternal obesity and gestational weight gain have a significant impact on maternal metabolism and offspring development. Insulin resistance, glucose homeostasis, fat oxidation and amino acid synthesis are all disrupted by maternal obesity and contribute to adverse outcomes. Modification of lifestyle is an effective intervention strategy for improvement of maternal metabolism and the prevention of type 2 diabetes and, potentially, gestational diabetes.

CONCLUSIONS

Maternal obesity requires the development of effective interventions to improve pregnancy outcome. Strategies that incorporate a detailed understanding of the maternal metabolic environment and its consequences for the health of the mother and the growth of the child are likely to identify the best approach.

A randomised control trial of low glycaemic index carbohydrate diet versus no dietary intervention in the prevention of recurrence of macrosomia

BACKGROUND

Maternal weight and maternal weight gain during pregnancy exert a significant influence on infant birth weight and the incidence of macrosomia. Fetal macrosomia is associated with an increase in both adverse obstetric and neonatal outcome, and also confers a future risk of childhood obesity. Studies have shown that a low glycaemic diet is associated with lower birth weights, however these studies have been small and not randomised 12. Fetal macrosomia recurs in a second pregnancy in one third of women, and maternal weight influences this recurrence risk 3.

METHODS/DESIGN

We propose a randomised control trial of low glycaemic index carbohydrate diet vs. no dietary intervention in the prevention of recurrence of fetal macrosomia. Secundigravid women whose first baby was macrosomic, defined as a birth weight greater than 4000 g will be recruited at their first antenatal visit.Patients will be randomised into two arms, a control arm which will receive no dietary intervention and a diet arm which will be commenced on a low glycaemic index diet.The primary outcome measure will be the mean birth weight centiles and ponderal indices in each group.

DISCUSSION

Altering the source of maternal dietary carbohydrate may prove to be valuable in the management of pregnancies where there has been a history of fetal macrosomia. Fetal macrosomia recurs in a second pregnancy in one third of women. This randomised control trial will investigate whether or not a low glycaemic index diet can affect this recurrence risk.

Management of maternal obesity prior to and during pregnancy

The prevalence of obesity is high and rising worldwide. The greatest prevalence of obesity is found in the western world and in urban developing countries. There is an increased maternal mortality associated with maternal obesity. There are increased risks of most maternal complications in pregnancy including pre-eclampsia, gestational and pre-existing type 2 diabetes mellitus and thromboembolic disorders. There is an increased perinatal mortality associated with maternal obesity; there are increased risks of congenital malformation, fetal macrosomia and indeed risks for the fetus as a child and adult in the years to come. There are increased risks of complications of pregnancy including caesarean section, traumatic delivery and a reduced chance of breastfeeding. Maternal obesity in pregnancy predicts long-term risks for that mother. The management includes increased surveillance for these risks and lifestyle modulation during pregnancy. This includes dietary measures and encouraging modest increase in exercise. Ideally, the mother should achieve closer to an ideal body mass index prior to pregnancy using lifestyle intervention but possibly with pharmacological therapy or bariatric surgery. The ideal weight gain for an obese mother is less than the ideal weight gain for a lean mother.

The influence of maternal glycaemia and dietary glycaemic index on pregnancy outcome in healthy mothers

Infant birth weight has increased in Ireland in recent years along with levels of childhood overweight and obesity. The present article reviews the current literature on maternal glycaemia and the role of the dietary glycaemic index (GI) and its impact on pregnancy outcomes. It is known that maternal weight and weight gain significantly influence infant birth weight. Fetal macrosomia (birth weight >4000 g) is associated with an increased risk of perinatal trauma to both mother and infant. Furthermore, macrosomic infants have greater risk of being obese in childhood, adolescence and adulthood compared to normal-sized infants. There is evidence that there is a direct relationship between maternal blood glucose levels during pregnancy and fetal growth and size at birth, even when maternal blood glucose levels are within their normal range. Thus, maintaining blood glucose concentrations within normal parameters during pregnancy may reduce the incidence of fetal macrosomia. Maternal diet, and particularly its carbohydrate (CHO) type and content, influences maternal blood glucose concentrations. However, different CHO foods produce different glycaemic responses. The GI was conceived by Jenkins in 1981 as a method for assessing the glycaemic responses of different CHO. Data from clinical studies in healthy pregnant women have documented that consuming a low-GI diet during pregnancy reduces peaks in postprandial glucose levels and normalises infant birth weight. Pregnancy is a physiological condition where the GI may be of particular relevance as glucose is the primary fuel for fetal growth.

Optimal dietary approaches for prevention of type 2 diabetes: a life-course perspective

In recent years, several alternative dietary approaches, including high-protein and low-glycaemic-load diets, have produced faster rates of weight loss than traditional low-fat, high-carbohydrate diets. These diets share an under-recognised unifying mechanism: the reduction of postprandial glycaemia and insulinaemia. Similarly, some food patterns and specific foods (potatoes, white bread, soft drinks) characterised by hyperglycaemia are associated with higher risk of adiposity and type 2 diabetes. Profound compensatory hyperinsulinaemia, exacerbated by overweight, occurs during critical periods of physiological insulin resistance such as pregnancy and puberty. The dramatic rise in gestational diabetes and type 2 diabetes in the young may therefore be traced to food patterns that exaggerate postprandial glycaemia and insulinaemia. The dietary strategy with the strongest evidence of being able to prevent type 2 diabetes is not the accepted low-fat, high-carbohydrate diet, but alternative dietary approaches that reduce postprandial glycaemia and insulinaemia without adversely affecting other risk factors.

Functional food for pregnant, lactating women and in perinatal nutrition: a role for dietary fibres?

PURPOSE OF REVIEW

If the benefits of dietary fibre in healthy adults have extensively been studied, little information is available on the specific needs of pregnant, lactating women or foetus. As far as infants are concerned, milk oligosaccharides are supposed to be the optimal 'dietary fibre'. The supplementation of infant formula with prebiotic oligosaccharides is still discussed. However, recent studies provide a large amount of information, allowing a new discussion on this topic.

RECENT FINDINGS

Most recent findings are linked to the involvement of dietary fibre in occurrence or prevention of obesity. The multiple mechanisms appear more clearly than earlier. This finding will soon allow appropriate counselling for young mothers at risk of obesity and/or postpartum retention weight, gestational diabetes and preeclampsia. Another area which benefits from recent research is the use of prebiotics in formula.

SUMMARY

Pregnancy is a critical period during which many physiologic changes occurred and is associated with several gut disorders and metabolic diseases. Dietary fibre may be helpful in the prevention and management of these diseases. Lactation and pregnancy are two phases during which food consumption of the mother can interact with the physiology of the baby. Moreover, the use of formula supplemented in oligosaccharides is able to compensate for the lack of some of the complex molecules naturally present in human milk.

Diet and deprivation in pregnancy

Deprivation is associated with poor pregnancy outcome but the role of nutrition as a mediating factor is not well understood. We carried out a prospective cohort study of 1461 singleton pregnancies in Aberdeen, UK during 2000-6. We measured nutrient intake and supplement use, B vitamin and homocysteine status, birth weight, gestational age, neonatal treatment and socio-economic deprivation status. Women in the most deprived deciles were approximately 6 years younger and half as likely to take folic acid supplements periconceptually as the least deprived mothers. Deprivation was associated with low blood folate, high homocysteine and diets low in protein, fibre and many of the vitamins and minerals. The diets of the more deprived women were also characterised by low intakes of fruit, vegetables and oily fish and higher intakes of processed meat, fried potatoes, crisps and snacks. Deprivation was related to preterm birth (OR 1.14 (95 % CI 1.03, 1.25); P = 0.009) and whether the baby required neonatal treatment (OR 1.07 (95 % CI 1.01, 1.14); P = 0.028). Low birth weight was more common in women consuming diets low in vitamin C (OR 0.79 (95 % CI 0.64, 0.97); P = 0.028), riboflavin (OR 0.77 (95 % CI 0.63, 0.93); P = 0.008), pantothenic acid (OR 0.79 (95 % CI 0.65, 0.97); P = 0.023) and sugars (OR 0.78 (95 % CI 0.64, 0.96); P = 0.017) even after adjustment for deprivation index, smoking, marital status and parity. Deprivation in pregnancy is associated with diets poor in specific nutrients and poor diet appears to contribute to inequalities in pregnancy outcome. Improving the nutrient intake of disadvantaged women of childbearing age may potentially improve pregnancy outcome.

The controversy continues: nutritional management of the pregnancy complicated by diabetes

Current controversies for medical nutrition therapy in pregnancies complicated by diabetes include the composition and amount of carbohydrates and fats as well as optimal gestational weight gain and energy restriction. Although carbohydrate is the macronutrient with the greatest effect on glycemic control, there is little evidence for a recommended amount and type of carbohydrate or its distribution. This lack of evidence prompts an issue of debate among practitioners over the type of carbohydrate and its percent distribution throughout the day. The best indicators at this time are the results of self-monitoring of blood glucose, ketone testing, food records, and weight gain. A review of the literature provides the most current information available for medical nutrition therapy during a pregnancy complicated by diabetes and reinforces the need for further research in the form of randomized controlled trials to answer questions regarding carbohydrate modification and distribution, energy needs, and weight gain.

The impact of gestational weight gain and diet on abnormal glucose tolerance during pregnancy in Hispanic women

OBJECTIVE

To examine the association of gestational weight gain and dietary factors with abnormal glucose tolerance (AGT).

METHODS

We conducted a prospective cohort study among 813 Hispanic prenatal care patients in Massachusetts. Gestational weight gain and oral glucose tolerance test results were abstracted from medical records. Dietary intake was assessed using a semi-quantitative food frequency questionnaire. Target weight gain was based on BMI-specific weekly weight gain rates established by the Institute of Medicine (IOM).

RESULTS

We observed a statistically significant interaction between prepregnancy BMI and weight gain in relation to AGT (P < 0.01). Class II/III (BMI > or = 35 kg/m2) obese women who had a high rate of weight gain (>0.30 kg/week) or who exceeded target weight were 3-4 times as likely to develop AGT compared to women who gained within IOM ranges (OR = 4.2, 95% CI 1.1-16.0, OR = 3.2 95% CI 1.0-10.5, respectively). Decreasing levels of saturated fatty acids and energy-dense snack foods and increasing levels of fiber and polyunsaturated:saturated fat ratio were significantly associated with decreased risk of AGT, independent of gestational weight gain [corrected].

CONCLUSIONS

Weight gain among class II/III obese women and certain dietary components may represent modifiable risk factors for AGT.

Can a low-glycemic index diet reduce the need for insulin in gestational diabetes mellitus? A randomized trial

OBJECTIVE

A low-glycemic index diet is effective as a treatment for individuals with diabetes and has been shown to improve pregnancy outcomes when used from the first trimester. A low-glycemic index diet is commonly advised as treatment for women with gestational diabetes mellitus (GDM). However, the efficacy of this advice and associated pregnancy outcomes have not been systematically examined. The purpose of this study was to determine whether prescribing a low-glycemic index diet for women with GDM could reduce the number of women requiring insulin without compromise of pregnancy outcomes.

RESEARCH DESIGN AND METHODS

All women with GDM seen over a 12-month period were considered for inclusion in the study. Women (n = 63) were randomly assigned to receive either a low-glycemic index diet or a conventional high-fiber (and higher glycemic index) diet.

RESULTS

Of the 31 women randomly assigned to a low-glycemic index diet, 9 (29%) required insulin. Of the women randomly assigned to a higher-glycemic index diet, a significantly higher proportion, 19 of 32 (59%), met the criteria to commence insulin treatment (P = 0.023). However, 9 of these 19 women were able to avoid insulin use by changing to a low-glycemic index diet. Key obstetric and fetal outcomes were not significantly different.

CONCLUSIONS

Using a low-glycemic index diet for women with GDM effectively halved the number needing to use insulin, with no compromise of obstetric or fetal outcomes.

Transient high glycaemic intake in the last trimester of pregnancy increases offspring birthweight and postnatal growth rate in sheep: a randomised control trial

OBJECTIVE

Investigate the effect of transient hyperglycemic intake (analogous to snacking on high glycaemic foods) in the third trimester of pregnancy on offspring birthweight and subsequent growth in sheep.

DESIGN

Randomised trial.

SETTING

University research farm.

SAMPLE

Third trimester pregnant ewes.

METHODS

Ewes were blocked on weight, age and litter size and were randomly assigned to receive oral administration of 100 ml of propylene glycol (PG; n = 51) or 100 ml of water (control, C; n = 53) twice/day. Twice during treatment, 12 ewes from each group were selected and blood samples collected to determine the glucose and insulin response to treatment.

MAIN OUTCOME MEASURES

At birth, blood was collected from the lambs, their body dimensions measured and body weights recorded at 0, 6 and 12 weeks of age after which lambs were slaughtered when they reached 40 kg live weight.

RESULTS

Administration of PG elevated (P < 0.05) plasma glucose and insulin concentrations for 2 hours post administration compared with control ewes. Lambs (C: n = 80; PG: n = 70) born to ewes fed high glycaemic meals had higher birthweights (C: 5.01 +/- 0.18 kg; PG: 5.27 +/- 0.22 kg, P = 0.032), plasma glucose concentrations (P = 0.001) and ponderal index (weight/height(3), P = 0.043) and reached a similar (P > 0.05) slaughter carcass weight (C: 20.0 +/- 0.51 kg; PG: 20.6 +/- 0.55 kg) at an earlier age (PG: 166.0 +/- 13.2; C: 183.4 +/- 13.8 days, P = 0.039) compared with control lambs.

CONCLUSIONS

Transient high glycaemic intakes in the third trimester of pregnancy resulted in heavier offspring at birth that had faster growth rates in early postnatal life. This animal model is relevant for studying the relationship between maternal diet, fetal size and the risk of childhood obesity.

The management of gestational diabetes

The incidence of gestational diabetes is increasing. As gestational diabetes is associated with adverse pregnancy outcomes, and has long-term implications for both mother and child, it is important that it is recognized and appropriately managed. This review will examine the pharmacological options for the management of gestational diabetes, as well as the evidence for blood glucose monitoring, dietary and exercise therapy. The medical management of gestational diabetes is still evolving, and recent randomized controlled trials have added considerably to our knowledge in this area. As insulin therapy is effective and safe, it is considered the gold standard of pharmacotherapy for gestational diabetes, against which other treatments have been compared. The current experience is that the short acting insulin analogs lispro and aspart are safe, but there are only limited data to support the use of long acting insulin analogs. There are randomized controlled trials which have demonstrated efficacy of the oral agents glyburide and metformin. Whilst short-term data have not demonstrated adverse effects of glyburide and metformin on the fetus, and they are increasingly being used in pregnancy, there remain long-term concerns regarding their potential for harm.

A foetal energy balance equation based on maternal exercise and diet

Empirical data indicate that the maternal diet composition has a direct impact on foetal fat mass and resulting birth weights. Weight-bearing maternal exercise influences the placental volume, which has also been correlated to birth weight. A foetal energy balance equation, based on the first law of thermodynamics, that incorporates maternal diet and exercise is developed. Model parameters and validity are evaluated using published data.

Dietary advice in pregnancy for preventing gestational diabetes mellitus

BACKGROUND

Gestational diabetes mellitus (GDM) is a form of diabetes that occurs during pregnancy which can result in significant adverse outcomes for mother and child both in the short and long term. The potential for adverse outcomes, in addition to the increasing prevalence of gestational diabetes worldwide, demonstrates the need to assess strategies, such as dietary advice, that might prevent gestational diabetes.

OBJECTIVES

To assess the effects of dietary advice in preventing gestational diabetes mellitus.

SEARCH STRATEGY

We searched the Cochrane Pregnancy and Childbirth Group's Trials Register (January 2008) and reference lists of retrieved articles.

SELECTION CRITERIA

Quasi-randomised and randomised studies of dietary intervention for preventing glucose intolerance in pregnancy.

DATA COLLECTION AND ANALYSIS

Two review authors independently conducted data extraction and quality assessment. We resolved disagreements through discussion or through a third author.

MAIN RESULTS

Three trials (107 women) were included in the review. One trial (25 pregnant women) analysed high-fibre diets with no included outcomes showing statistically significant differences. Two trials (82 pregnant women) assessed low glycaemic index (LGI) versus high glycaemic index diets for pregnant women. Women on the LGI diet had fewer large for gestational age infants (one trial; relative risk (RR) 0.09, 95% confidence interval (CI) 0.01 to 0.69), infants with lower ponderal indexes (two trials; weighted mean difference (WMD) -0.18, 95% CI -0.32 to -0.04, random-effects analysis) and lower maternal fasting glucose levels (two trials; WMD -0.28 mmol/L 95% CI -0.54 to -0.02, random-effects model). Results for women on the LGI diet on neonatal birth weight were not conclusive under a random-effects model (two trials; WMD -527.64 g, 95% CI -1119.20 to 63.92); however, on a fixed-effect model, women on the LGI diet gave birth to lighter babies (two trials; WMD -445.55 g, 95% CI -634.16 to -256.95). High heterogeneity was observed between the trials in most results and both were relatively small trials. One of these trials also included a standard exercise regimen for all participants.

AUTHORS' CONCLUSIONS

While a low glycaemic index diet was seen to be beneficial for some outcomes for both mother and child, results from the review were inconclusive. Further trials with large sample sizes and longer follow up are required to make more definitive conclusions. No conclusions could be drawn from the high-fibre versus control-diet comparison since the trial involved did not report on many of the outcomes we prespecified.

Size at birth, obesity and blood pressure at age five

BACKGROUND

The fetal origins hypothesis indicates that morphometric evidence of fetal nutritional deprivation is predictive of excessive weight gain/obesity, insulin resistance, and cardiovascular disease after birth. However, it is unclear whether these effects are present in offspring with "normal" birth weights in contemporary Western society, whether they are population specific, and how early in life they appear. This study was designed to examine these questions in a select populace of morphometrically diverse offspring to test the null hypothesis that morphometric evidence of nutritional restriction in utero has no effect on the presence of either obesity or increased blood pressure at ages 5 and 6.

METHODS

We present a prospective study of 101 offspring born of well-nourished, middle and upper socioeconomic-class women who participated in studies of diet and exercise during pregnancy. At birth and age 5 to 6 the offspring underwent morphometric evaluation with the additional measurement of blood pressure at age 5 to 6.

RESULTS

There were no significant negative correlations between neonatal morphometrics and either blood pressure or obesity at age 5 to 6. There were, however, direct positive correlations between birth weight and both weight and BMI at age 5 to 6 (p < 0.0001).

CONCLUSIONS

In this specific populace, morphometrics at age 5 to 6 correlated with size at birth. However, there was no relationship between mophometric evidence of in utero nutritional deprivation at birth and either blood pressure or obesity at age 5 to 6.

State of the Art Reviews: Nutrition and Lifestyle for a Healthy Pregnancy

Nutrition and lifestyle factors can maximize health in pregnancy and lower future risk of disease for both mother and fetus. Education can make a big difference for patients in pregnancy outcomes, anxiety, and future health. Pregnancy is a time when attention to proper weight gain can reduce the risk of future obesity, diabetes, hyperlipidemia, and cardiovascular disease. There is mounting evidence that fetal “programming” for future risk of disease begins in utero and varies with nutritional exposures during different times of pregnancy, although the exact mechanisms remain to be elucidated. It is clear that a few simple precautions and enhancements of diet and lifestyle can prevent birth defects and perinatal infections and may reduce future health risks. Exercise in pregnancy is safe and should be encouraged for healthy women.

State of the Art Reviews: Glycemic Index, Obesity, and Chronic Disease

There is increasing evidence that both the amount and type of carbohydrate play an important role in weight management and risk of chronic disease. Classifying carbohydrates according to their post-prandial glycemic effect (ie, the glycemic index of foods) has yielded more useful insights than the historical distinctions of simple versus complex chemical structure. Diets based on carbohydrate foods that are more slowly digested and absorbed (ie, low glycemic index diets) have been independently linked to reduced risk of type 2 diabetes, cardiovascular disease, and some types of cancer. In individuals with diabetes, intervention studies have shown improvements in insulin sensitivity and glycated hemoglobin concentration with low glycemic index diets. Research also suggests that low glycemic index diets may assist with weight management through effects on satiety and fuel partitioning. Although ongoing research is needed, the current findings, together with the fact that there are no demonstrated negative effects of a low glycemic index diet, suggest that the glycemic index should be an important consideration in the dietary management and prevention of obesity and chronic disease.

Dietary effects on fertility treatment and pregnancy outcomes

PURPOSE OF REVIEW

We summarize the dietary modifications that optimize fertility treatment outcomes.

RECENT FINDINGS

Body weight and nutritional status are closely related to reproductive function. However, few studies have investigated the direct effects of dietary modification on fertility treatment outcomes. Research on nutrition in pregnancy suggests that reduction in glycemic load and micronutrient supplementation may improve pregnancy outcomes.

SUMMARY

Body weight and specific dietary factors may affect fertility but evidence regarding dietary effects on fertility treatment outcomes is lacking. Research suggests that diets with a low glycemic load during pregnancy may reduce the risk of gestational diabetes or large-for-gestational-age births after adjusting for body mass index and total energy intake, but the effect of protein modification remains controversial. There is also lack of information on the impact of energy restriction during pregnancy on maternal and infant outcomes. Folate supplementation is recommended for prevention of birth defects but further research is required to determine the optimal dose to reduce the risks of multiple gestations. Further information on the upper limits of caffeine and alcohol intake during pregnancy would also be useful.

Programming of body composition by early growth and nutrition

There is now compelling evidence that growth patterns in early life are associated with risk of the metabolic syndrome in adulthood, although the relative importance of prenatal v. postnatal growth for such associations remains controversial. Body composition may play a key role in the ‘programming’ of such diseases, through itself being programmed by early growth, and perhaps also by being a mediator of the programming process. Early studies reporting positive associations between birth weight and adult BMI suggested a tendency for large babies to become obese adults. Such findings appeared contradictory to the many studies linking low birth weight with increased risk of the metabolic syndrome. Recent studies now indicate that birth weight is strongly predictive of later lean mass, and has a much weaker association with later fatness. Studies that link low birth weight with a more central adipose distribution in later life remain controversial, and require confirmation using more sophisticated methodologies. Findings for infant growth rate appear population-specific, with infant weight gain predicting subsequent lean mass in developing countries, but predicting subsequent fat mass and obesity in industrialised populations. Further studies are required on this issue, to ensure that appropriate public health policies are recommended for countries across the range of economic development. Although the links between early growth and later disease risk implicate early-life nutrition, either in utero or during infancy, few prospective studies have explored the influence of early diet on later body composition. Many studies have associated breast-feeding with a reduced prevalence of obesity categorised by BMI; however, the few studies directly evaluating childhood fatness provide little support for this hypothesis. Recent advances in the ability to measure body composition during the infant period offer a major opportunity to improve the understanding of the nutritional programming of body composition and its contribution, or lack thereof, to subsequent disease risk.

Energy and protein intake in pregnancy

BACKGROUND

Gestational weight gain is positively associated with fetal growth, and observational studies of food supplementation in pregnancy have reported increases in gestational weight gain and fetal growth.

OBJECTIVES

To assess the effects of advice to increase or reduce energy or protein intake, or of actual energy or protein supplementation or restriction, during pregnancy on energy and protein intakes, gestational weight gain, and the outcome of pregnancy.

SEARCH STRATEGY

We searched the Cochrane Pregnancy and Childbirth Group trials register (October 2002) and contacted researchers in the field.

SELECTION CRITERIA

Acceptably controlled trials of dietary advice to increase or reduce energy or protein intake, or of actual energy or protein supplementation or restriction, during pregnancy.

DATA COLLECTION AND ANALYSIS

Data were extracted by the authors from published reports, and supplemented by additional information from trialists contacted by the authors.

MAIN RESULTS

In five trials involving 1134 women, nutritional advice to increase energy and protein intakes was successful in achieving those goals, but no consistent benefit was observed on pregnancy outcomes. In 13 trials involving 4665 women, balanced energy/protein supplementation was associated with modest increases in maternal weight gain and in mean birth weight, and a substantial reduction in risk of small-for-gestational-age (SGA) birth. These effects did not appear greater in undernourished women. No significant effects were detected on preterm birth, but significantly reduced risks were observed for stillbirth and neonatal death. In two trials involving 1076 women, high-protein supplementation was associated with a small, nonsignificant increase in maternal weight gain but a nonsignificant reduction in mean birthweight, a significantly increased risk of SGA birth, and a nonsignificantly increased risk of neonatal death. In 3 trials involving 966 women, isocaloric protein supplementation was also associated with an increased risk of SGA birth. In three trials involving 384 women, energy/protein restriction of pregnant women who were overweight or exhibited high weight gain significantly reduced weekly maternal weight gain and mean birth weight but had no effect on pregnancy-induced hypertension or pre-eclampsia.

REVIEWER'S CONCLUSIONS

Dietary advice appears effective in increasing pregnant women's energy and protein intakes but is unlikely to confer major benefits on infant or maternal health. Balanced energy/protein supplementation improves fetal growth and may reduce the risk of fetal and neonatal death. High-protein or balanced protein supplementation alone is not beneficial and may be harmful to the infant.Protein/energy restriction of pregnant women who are overweight or exhibit high weight gain is unlikely to be beneficial and may be harmful to the infant.