Metabolic effects of hypocaloric diets in management of gestational diabetes

The Carbohydrate Threshold in Pregnancy and Gestational Diabetes: How Low Can We Go?

The original nutrition approach for the treatment of gestational diabetes mellitus (GDM) was to reduce total carbohydrate intake to 33–40% of total energy (EI) to decrease fetal overgrowth. Conversely, accumulating evidence suggests that higher carbohydrate intakes (60–70% EI, higher quality carbohydrates with low glycemic index/low added sugars) can control maternal glycemia. The Institute of Medicine (IOM) recommends ≥175 g/d of carbohydrate intake during pregnancy; however, many women are consuming lower carbohydrate (LC) diets (<175 g/d of carbohydrate or <40% of EI) within pregnancy and the periconceptual period aiming to improve glycemic control and pregnancy outcomes. This report systematically evaluates recent data (2018–2020) to identify the LC threshold in pregnancy in relation to safety considerations. Evidence from 11 reports suggests an optimal carbohydrate range of 47–70% EI supports normal fetal growth; higher than the conventionally recognized LC threshold. However, inadequate total maternal EI, which independently slows fetal growth was a frequent confounder across studies. Effects of a carbohydrate intake <175 g/d on maternal ketonemia and plasma triglyceride/free fatty acid concentrations remain unclear. A recent randomized controlled trial (RCT) suggests a higher risk for micronutrient deficiency with carbohydrate intake ≤165 g/d in GDM. Well-controlled prospective RCTs comparing LC (<165 g/d) and higher carbohydrate energy-balanced diets in pregnant women are clearly overdue.

Effects of a modestly lower carbohydrate diet in gestational diabetes: a randomized controlled trial

BACKGROUND

Lower carbohydrate diets have the potential to improve glycemia but may increase ketonemia in women with gestational diabetes (GDM). We hypothesized that modestly lower carbohydrate intake would not increase ketonemia.

OBJECTIVE

To compare blood ketone concentration, risk of ketonemia, and pregnancy outcomes in women with GDM randomly assigned to a lower carbohydrate diet or routine care.

METHODS

Forty-six women aged (mean ± SEM) 33.3 ± 0.6 y and prepregnancy BMI 26.8 ± 0.9 kg/m2 were randomly assigned at 28.5 ± 0.4 wk to a modestly lower carbohydrate diet (MLC, ∼135 g/d carbohydrate) or routine care (RC, ∼200 g/d) for 6 wk. Blood ketones were ascertained by finger prick test strips and 3-d food diaries were collected at baseline and end of the intervention.

RESULTS

There were no detectable differences in blood ketones between completers in the MLC group compared with the RC group (0.1 ± 0.0 compared with 0.1 ± 0.0 mmol/L, n = 33, P = 0.31, respectively), even though carbohydrate and total energy intake were significantly lower in the intervention group (carbohydrate 165 ± 7 compared with 190 ± 9 g, P = 0.04; energy 7040 ± 240 compared with 8230 ± 320 kJ, P <0.01, respectively). Only 20% of participants in the MLC group met the target intake compared with 65% in the RC group (P <0.01). There were no differences in birth weight, rate of large-for-gestational-age infants, percent fat mass, or fat-free mass between groups.

CONCLUSIONS

An intervention to reduce carbohydrate intake in GDM did not raise ketones to clinical significance, possibly because the target of 135 g/d was difficult to achieve in pregnancy. Feeding studies with food provision may be needed to assess the benefits and risks of low-carbohydrate diets. This trial was registered at www.anzctr.org.au as ACTRN12616000018415.

Interventions to prevent women from developing gestational diabetes mellitus: an overview of Cochrane Reviews

BACKGROUND

The prevalence of gestational diabetes mellitus (GDM) is increasing, with approximately 15% of pregnant women affected worldwide, varying by country, ethnicity and diagnostic thresholds. There are associated short- and long-term health risks for women and their babies.

OBJECTIVES

We aimed to summarise the evidence from Cochrane systematic reviews on the effects of interventions for preventing GDM.

METHODS

We searched the Cochrane Database of Systematic Reviews (6 August 2019) with key words 'gestational diabetes' OR 'GDM' to identify reviews pre-specifying GDM as an outcome. We included reviews of interventions in women who were pregnant or planning a pregnancy, irrespective of their GDM risk status. Two overview authors independently assessed eligibility, extracted data and assessed quality of evidence using ROBIS and GRADE tools. We assigned interventions to categories with graphic icons to classify the effectiveness of interventions as: clear evidence of benefit or harm (GRADE moderate- or high-quality evidence with a confidence interval (CI) that did not cross the line of no effect); clear evidence of no effect or equivalence (GRADE moderate- or high-quality evidence with a narrow CI crossing the line of no effect); possible benefit or harm (low-quality evidence with a CI that did not cross the line of no effect or GRADE moderate- or high-quality evidence with a wide CI); or unknown benefit or harm (GRADE low-quality evidence with a wide CI or very low-quality evidence).

MAIN RESULTS

We included 11 Cochrane Reviews (71 trials, 23,154 women) with data on GDM. Nine additional reviews pre-specified GDM as an outcome, but did not identify GDM data in included trials. Ten of the 11 reviews were judged to be at low risk of bias and one review at unclear risk of bias. Interventions assessed included diet, exercise, a combination of diet and exercise, dietary supplements, pharmaceuticals, and management of other health problems in pregnancy. The quality of evidence ranged from high to very low. Diet Unknown benefit or harm: there was unknown benefit or harm of dietary advice versus standard care, on the risk of GDM: risk ratio (RR) 0.60, 95% CI 0.35 to 1.04; 5 trials; 1279 women; very low-quality evidence. There was unknown benefit or harm of a low glycaemic index diet versus a moderate-high glycaemic index diet on the risk of GDM: RR 0.91, 95% CI 0.63 to 1.31; 4 trials; 912 women; low-quality evidence. Exercise Unknown benefit or harm: there was unknown benefit or harm for exercise interventions versus standard antenatal care on the risk of GDM: RR 1.10, 95% CI 0.66 to 1.84; 3 trials; 826 women; low-quality evidence. Diet and exercise combined Possible benefit: combined diet and exercise interventions during pregnancy versus standard care possibly reduced the risk of GDM: RR 0.85, 95% CI 0.71 to 1.01; 19 trials; 6633 women; moderate-quality evidence. Dietary supplements Clear evidence of no effect: omega-3 fatty acid supplementation versus none in pregnancy had no effect on the risk of GDM: RR 1.02, 95% CI 0.83 to 1.26; 12 trials; 5235 women; high-quality evidence. Possible benefit: myo-inositol supplementation during pregnancy versus control possibly reduced the risk of GDM: RR 0.43, 95% CI 0.29 to 0.64; 3 trials; 502 women; low-quality evidence. Possible benefit: vitamin D supplementation versus placebo or control in pregnancy possibly reduced the risk of GDM: RR 0.51, 95% CI 0.27 to 0.97; 4 trials; 446 women; low-quality evidence. Unknown benefit or harm: there was unknown benefit or harm of probiotic with dietary intervention versus placebo with dietary intervention (RR 0.37, 95% CI 0.15 to 0.89; 1 trial; 114 women; very low-quality evidence), or probiotic with dietary intervention versus control (RR 0.38, 95% CI 0.16 to 0.92; 1 trial; 111 women; very low-quality evidence) on the risk of GDM. There was unknown benefit or harm of vitamin D + calcium supplementation versus placebo (RR 0.33, 95% CI 0.01 to 7.84; 1 trial; 54 women; very low-quality evidence) or vitamin D + calcium + other minerals versus calcium + other minerals (RR 0.42, 95% CI 0.10 to 1.73; 1 trial; 1298 women; very low-quality evidence) on the risk of GDM. Pharmaceutical Possible benefit: metformin versus placebo given to obese pregnant women possibly reduced the risk of GDM: RR 0.85, 95% CI 0.61 to 1.19; 3 trials; 892 women; moderate-quality evidence. Unknown benefit or harm:eight small trials with low- to very low-quality evidence showed unknown benefit or harm for heparin, aspirin, leukocyte immunisation or IgG given to women with a previous stillbirth on the risk of GDM. Management of other health issues Clear evidence of no effect: universal versus risk based screening of pregnant women for thyroid dysfunction had no effect on the risk of GDM: RR 0.93, 95% CI 0.70 to 1.25; 1 trial; 4516 women; moderate-quality evidence. Unknown benefit or harm: there was unknown benefit or harm of using fractional exhaled nitrogen oxide versus a clinical algorithm to adjust asthma therapy on the risk of GDM: RR 0.74, 95% CI 0.31 to 1.77; 1 trial; 210 women; low-quality evidence. There was unknown benefit or harm of pharmacist led multidisciplinary approach to management of maternal asthma versus standard care on the risk of GDM: RR 5.00, 95% CI 0.25 to 99.82; 1 trial; 58 women; low-quality evidence.

AUTHORS' CONCLUSIONS

No interventions to prevent GDM in 11 systematic reviews were of clear benefit or harm. A combination of exercise and diet, supplementation with myo-inositol, supplementation with vitamin D and metformin were of possible benefit in reducing the risk of GDM, but further high-quality evidence is needed. Omega-3-fatty acid supplementation and universal screening for thyroid dysfunction did not alter the risk of GDM. There was insufficient high-quality evidence to establish the effect on the risk of GDM of diet or exercise alone, probiotics, vitamin D with calcium or other vitamins and minerals, interventions in pregnancy after a previous stillbirth, and different asthma management strategies in pregnancy. There is a lack of trials investigating the effect of interventions prior to or between pregnancies on risk of GDM.

Diet and Nutritional Interventions with the Special Role of Myo-Inositol in Gestational Diabetes Mellitus Management. An Evidence-Based Critical Appraisal

BACKGROUND

Gestational Diabetes Mellitus (GDM), defined as glucose intolerance with onset or first recognition during pregnancy, represents one of the most common maternal-fetal complications during pregnancy and it is associated with poor perinatal outcomes. To date, GDM is a rising condition over the last decades coinciding with the ongoing epidemic of obesity and Type 2 Diabetes Mellitus (T2DM).

OBJECTIVE

The aim of this review is to discuss the role of diet and nutritional interventions in preventing GDM with the explanation of the special role of myo-inositol (MI) in this matter.

METHODS

We performed an overview of the most recent literature data on the subject with particular attention to the effectiveness of diet and nutritional interventions in the prevention of GDM with the special role of MI.

RESULTS

Nutritional intervention and physical activity before and during pregnancy are mandatory in women affected by GDM. Moreover, the availability of insulin-sensitizers such as different forms of inositol has dramatically changed the scenario, allowing the treatment of several metabolic diseases, such as those related to glucose dysbalance. Although the optimal dose, frequency, and form of MI administration need to be further investigated, diet supplementation with MI appears to be an attractive alternative for the GDM prevention as well as for the reduction of GDM-related complications.

CONCLUSIONS

More studies should be conducted to prove the most effective nutritional intervention in GDM. Regarding the potential effectiveness of MI, further evidence in multicenter, randomized controlled trials is needed to draw firm conclusions.

Interventions to prevent women developing gestational diabetes mellitus: an overview of Cochrane Reviews

This is a protocol for a Cochrane Review (Overview). The objectives are as follows:

To summarise the evidence from Cochrane systematic reviews regarding the effects of interventions to prevent women developing gestational diabetes mellitus (GDM).

Dietary advice interventions in pregnancy for preventing gestational diabetes mellitus

BACKGROUND

Gestational diabetes mellitus (GDM) is a form of diabetes occurring during pregnancy which can result in short- and long-term adverse outcomes for women and babies. With an increasing prevalence worldwide, there is a need to assess strategies, including dietary advice interventions, that might prevent GDM.

OBJECTIVES

To assess the effects of dietary advice interventions for preventing GDM and associated adverse health outcomes for women and their babies.

SEARCH METHODS

We searched Cochrane Pregnancy and Childbirth's Trials Register (3 January 2016) and reference lists of retrieved studies.

SELECTION CRITERIA

Randomised controlled trials (RCTs) and quasi-RCTs assessing the effects of dietary advice interventions compared with no intervention (standard care), or to different dietary advice interventions. Cluster-RCTs were eligible for inclusion but none were identified.

DATA COLLECTION AND ANALYSIS

Two review authors independently assessed study eligibility, extracted data and assessed the risk of bias of the included studies. Data were checked for accuracy. The quality of the evidence was assessed using the GRADE approach.

MAIN RESULTS

We included 11 trials involving 2786 women and their babies, with an overall unclear to moderate risk of bias. Six trials compared dietary advice interventions with standard care; four compared low glycaemic index (GI) with moderate- to high-GI dietary advice; one compared specific (high-fibre focused) with standard dietary advice. Dietary advice interventions versus standard care (six trials) Considering primary outcomes, a trend towards a reduction in GDM was observed for women receiving dietary advice compared with standard care (average risk ratio (RR) 0.60, 95% confidence interval (CI) 0.35 to 1.04; five trials, 1279 women; Tau² = 0.20; I² = 56%; P = 0.07; GRADE: very low-quality evidence); subgroup analysis suggested a greater treatment effect for overweight and obese women receiving dietary advice. While no clear difference was observed for pre-eclampsia (RR 0.61, 95% CI 0.25 to 1.46; two trials, 282 women; GRADE: low-quality evidence) a reduction in pregnancy-induced hypertension was observed for women receiving dietary advice (RR 0.30, 95% CI 0.10 to 0.88; two trials, 282 women; GRADE: low-quality evidence). One trial reported on perinatal mortality, and no deaths were observed (GRADE: very low-quality evidence). None of the trials reported on large-for-gestational age or neonatal mortality and morbidity.For secondary outcomes, no clear differences were seen for caesarean section (average RR 0.98, 95% CI 0.78 to 1.24; four trials, 1194 women; Tau² = 0.02; I² = 36%; GRADE: low-quality evidence) or perineal trauma (RR 0.83, 95% CI 0.23 to 3.08; one trial, 759 women; GRADE: very low-quality evidence). Women who received dietary advice gained less weight during pregnancy (mean difference (MD) -4.70 kg, 95% CI -8.07 to -1.34; five trials, 1336 women; Tau² = 13.64; I² = 96%; GRADE: low-quality evidence); the result should be interpreted with some caution due to considerable heterogeneity. No clear differences were seen for the majority of secondary outcomes reported, including childhood/adulthood adiposity (skin-fold thickness at six months) (MD -0.10 mm, 95% CI -0.71 to 0.51; one trial, 132 children; GRADE: low-quality evidence). Women receiving dietary advice had a lower well-being score between 14 and 28 weeks, more weight loss at three months, and were less likely to have glucose intolerance (one trial).The trials did not report on other secondary outcomes, particularly those related to long-term health and health service use and costs. We were not able to assess the following outcomes using GRADE: postnatal depression; maternal type 2 diabetes; neonatal hypoglycaemia; childhood/adulthood type 2 diabetes; and neurosensory disability. Low-GI dietary advice versus moderate- to high-GI dietary advice (four trials) Considering primary outcomes, no clear differences were shown in the risks of GDM (RR 0.91, 95% CI 0.63 to 1.31; four trials, 912 women; GRADE: low-quality evidence) or large-for-gestational age (average RR 0.60, 95% CI 0.19 to 1.86; three trials, 777 babies; Tau² = 0.61; P = 0.07; I² = 62%; GRADE: very low-quality evidence) between the low-GI and moderate- to high-GI dietary advice groups. The trials did not report on: hypertensive disorders of pregnancy; perinatal mortality; neonatal mortality and morbidity.No clear differences were shown for caesarean birth (RR 1.27, 95% CI 0.79 to 2.04; two trials, 201 women; GRADE: very low-quality evidence) and gestational weight gain (MD -1.23 kg, 95% CI -4.08 to 1.61; four trials, 787 women; Tau² = 7.31; I² = 90%; GRADE: very low-quality evidence), or for other reported secondary outcomes.The trials did not report the majority of secondary outcomes including those related to long-term health and health service use and costs. We were not able to assess the following outcomes using GRADE: perineal trauma; postnatal depression; maternal type 2 diabetes; neonatal hypoglycaemia; childhood/adulthood adiposity; type 2 diabetes; and neurosensory disability. High-fibre dietary advice versus standard dietary advice (one trial) The one trial in this comparison reported on two secondary outcomes. No clear difference between the high-fibre and standard dietary advice groups observed for mean blood glucose (following an oral glucose tolerance test at 35 weeks), and birthweight.

AUTHORS' CONCLUSIONS

Very low-quality evidence from five trials suggests a possible reduction in GDM risk for women receiving dietary advice versus standard care, and low-quality evidence from four trials suggests no clear difference for women receiving low- versus moderate- to high-GI dietary advice. A possible reduction in pregnancy-induced hypertension for women receiving dietary advice was observed and no clear differences were seen for other reported primary outcomes. There were few outcome data for secondary outcomes.For outcomes assessed using GRADE, evidence was considered to be low to very low quality, with downgrading based on study limitations (risk of bias), imprecision, and inconsistency.More high-quality evidence is needed to determine the effects of dietary advice interventions in pregnancy. Future trials should be designed to monitor adherence, women's views and preferences, and powered to evaluate effects on short- and long-term outcomes; there is a need for such trials to collect and report on core outcomes for GDM research. We have identified five ongoing studies and four are awaiting classification. We will consider these in the next review update.

Interventions for preventing gestational diabetes mellitus: an overview of Cochrane Reviews

This is the protocol for a review and there is no abstract. The objectives are as follows:

To summarise the evidence from Cochrane systematic Reviews regarding the effects of interventions for preventing gestational diabetes mellitus.

Pandemic of Pregnant Obese Women: Is It Time to Re-Evaluate Antenatal Weight Loss?

The Obesity pandemic will afflict future generations without successful prevention, intervention and management. Attention to reducing obesity before, during and after pregnancy is essential for mothers and their offspring. Preconception weight loss is difficult given that many pregnancies are unplanned. Interventions aimed at limiting gestational weight gain have produced minimal maternal and infant outcomes. Therefore, increased research to develop evidence-based clinical practice is needed to adequately care for obese pregnant women especially during antenatal care. This review evaluates the current evidence of obesity interventions during pregnancy various including weight loss for safety and efficacy. Recommendations are provided with the end goal being a healthy pregnancy, optimal condition for breastfeeding and prevent the progression of obesity in future generations.

Gestational diabetes mellitus: challenges in diagnosis and management

Gestational diabetes mellitus (GDM) is a well-characterized disease affecting a significant population of pregnant women worldwide. It has been widely linked to undue weight gain associated with factors such as diet, obesity, family history, and ethnicity. Poorly controlled GDM results in maternal and fetal morbidity and mortality. Improved outcomes therefore rely on early diagnosis and tight glycaemic control. While straightforward protocols exist for screening and management of diabetes mellitus in the general population, management of GDM remains controversial with conflicting guidelines and treatment protocols. This review highlights the diagnostic and management options for GDM in light of recent advances in care.

Placental dysfunction in obese women and antenatal surveillance strategies

This review is aimed at discussing placental dysfunction in obesity and its clinical implication in pregnancy as well as an antenatal surveillance strategy for these women. Maternal obesity is associated with adverse perinatal outcome. Obesity is an independent risk factor for fetal hyperinsulinaemia, birthweight and newborn adiposity. Maternal obesity is associated with childhood obesity and obesity in adult life. Obesity induces a low-grade inflammatory response in placenta, which results in short- and long-term programming of obesity in fetal life. Preconception and antenatal counselling on obstetrics risk in pregnancy, on diet and lifestyle in pregnancy and on gestational weight gain is associated with a better outcome. Fetal growth velocity is closely associated with maternal weight and gestational weight gain. Careful monitoring of gestational weight gain and fetal growth, and screening and management of obstetrical complications such as gestational diabetes and pre-eclampsia, improves perinatal outcome. The use of metformin in non-diabetic obese women is under investigation; further evidence is required before recommending it.

The first trimester: prediction and prevention of the great obstetrical syndromes

A number of groups are currently examining the potential of screening for pre-eclampsia and gestational diabetes at 12 weeks' gestation. This can be performed at the time of combined first-trimester screening for aneuploidy using a similar method of regression analysis to combine multiple demographic and investigative factors. At present, research into the prediction of pre-eclampsia is more robust and is associated with the potential for therapeutic intervention that can reduce the prevalence of early-onset pre-eclampsia and improve maternal and neonatal outcomes.

The Treatment of Obese Pregnant Women (TOP) study: a randomized controlled trial of the effect of physical activity intervention assessed by pedometer with or without dietary intervention in obese pregnant women

OBJECTIVE

The objective of the study was to assess physical activity intervention assessed by a pedometer with or without dietary intervention on gestational weight gain (GWG) in obese pregnant women by comparing with a control group.

STUDY DESIGN

This study was a randomized controlled trial of 425 obese pregnant women comparing 3 groups: (1) PA plus D, physical activity and dietary intervention (n = 142); (2) PA, physical activity intervention (n = 142); and (3) C, a control group receiving standard care (n = 141). All participants routinely in gestational weeks 11-14 had an initial dietary counseling session and were advised to limit GWG to less than 5 kg. Physical activity intervention included encouragement to increase physical activity, aiming at a daily step count of 11,000, monitored by pedometer assessment on 7 consecutive days every 4 weeks. Dietary intervention included follow-up on a hypocaloric Mediterranean-style diet. Instruction was given by a dietician every 2 weeks. The primary outcome measure was GWG, and the secondary outcome measures were complications of pregnancy and delivery and neonatal outcome.

RESULTS

The study was completed by 389 patients (92%). Median values of GWG (ranges) were lower in each of the intervention groups (PA plus D, 8.6 [-9.6 to 34.1] kg, and group PA, 9.4 [-3.4 to 28.2] kg) compared with the control group (10.9 [-4.4 to 28.7] kg [PA+D vs C]; P = .01; PA vs C; P = .042). No significant difference was found between the 2 intervention groups. In a multivariate analysis, physical activity intervention decreased GWG by a mean of 1.38 kg (P = .040). The Institute of Medicine's recommendations for GWG were more frequently followed in the intervention groups.

CONCLUSION

Physical activity intervention assessed by pedometer with or without dietary follow-up reduced GWG compared with controls in obese pregnant women.

Determinants of maternal triglycerides in women with gestational diabetes mellitus in the Metformin in Gestational Diabetes (MiG) study

OBJECTIVE

Factors associated with increasing maternal triglyceride concentrations in late pregnancy include gestational age, obesity, preeclampsia, and altered glucose metabolism. In a subgroup of women in the Metformin in Gestational Diabetes (MiG) trial, maternal plasma triglycerides increased more between enrollment (30 weeks) and 36 weeks in those treated with metformin compared with insulin. The aim of this study was to explain this finding by examining factors potentially related to triglycerides in these women.

RESEARCH DESIGN AND METHODS

Of the 733 women randomized to metformin or insulin in the MiG trial, 432 (219 metformin and 213 insulin) had fasting plasma triglycerides measured at enrollment and at 36 weeks. Factors associated with maternal triglycerides were assessed using general linear modeling.

RESULTS

Mean plasma triglyceride concentrations were 2.43 (95% CI 2.35-2.51) mmol/L at enrollment. Triglycerides were higher at 36 weeks in women randomized to metformin (2.94 [2.80-3.08] mmol/L; +23.13% [18.72-27.53%]) than insulin (2.65 [2.54-2.77] mmol/L, P = 0.002; +14.36% [10.91-17.82%], P = 0.002). At 36 weeks, triglycerides were associated with HbA1c (P = 0.03), ethnicity (P = 0.001), and treatment allocation (P = 0.005). In insulin-treated women, 36-week triglycerides were associated with 36-week HbA1c (P = 0.02), and in metformin-treated women, they were related to ethnicity.

CONCLUSIONS

At 36 weeks, maternal triglycerides were related to glucose control in women treated with insulin and ethnicity in women treated with metformin. Whether there are ethnicity-related dietary changes or differences in metformin response that alter the relationship between glucose control and triglycerides requires further study.

Gestational diabetes mellitus

Gestational diabetes mellitus is one of the most common medical problems that results from an increase in the insulin resistance as well as an impairment of the compensatory increase in insulin secretion from the beta cells of the pancreas. It serves as a metabolic stress test that uncovers underlying insulin resistance and beta-cell dysfunction. Gestational diabetes is associated with a variety of maternal and fetal complications, most notably macrosomia. Controversy surrounds the ideal approach for detecting gestational diabetes, andthe approaches recommended for screening and diagnosis are largely based on expert opinion. Controlling maternal glycemia with Medical Nutrition Therapy, close monitoring of blood glucose levels and treatment with insulin if blood glucose levels are not at goal has been shown to decrease fetal and maternal morbidities. Other treatment modalities, such as oral agents, need further study to validate their safety and efficacy. Finally, postpartum management of women with Gestational diabetes is critical because of their markedly increased risk of Type 2 diabetes in the future. Efforts should be made to prevent gestational diabetes in subsequent pregnancies. Because body fat and diet contribute to the risk of gestational diabetes mellitus, patients who lose weight before pregnancy and follow an appropriate diet may lower their risk of gestational diabetes mellitus.

Gestational diabetes mellitus: risks and management during and after pregnancy

Gestational diabetes mellitus (GDM) carries a small but potentially important risk of adverse perinatal outcomes and a long-term risk of obesity and glucose intolerance in offspring. Mothers with GDM have an excess of hypertensive disorders during pregnancy and a high risk of developing diabetes mellitus thereafter. Diagnosing and treating GDM can reduce perinatal complications, but only a small fraction of pregnancies benefit. Nutritional management is the cornerstone of treatment; insulin, glyburide and metformin can be used to intensify treatment. Fetal measurements complement maternal glucose monitoring in the identification of pregnancies that require such intensification. Glucose testing shortly after delivery can stratify the short-term diabetes risk in mothers. Thereafter, annual glucose and HbA(1c) testing can detect deteriorating glycaemic control, a harbinger of future diabetes mellitus, usually type 2 diabetes mellitus. Interventions that mitigate obesity or its metabolic effects are most potent in preventing or delaying diabetes mellitus. Lifestyle modification is the primary approach; use of medications for diabetes prevention after GDM remains controversial. Family planning enables optimization of health in subsequent pregnancies. Breastfeeding may reduce obesity in children and is recommended. Families should be encouraged to help children adopt lifestyles that reduce the risk of obesity.

Diabetes gestacional: um algoritmo de tratamento multidisciplinar

O tratamento do diabetes gestacional é importante para evitar a morbimortalidade materno-fetal. O objetivo deste artigo é descrever o tratamento atualmente disponível para o manejo otimizado da hiperglicemia na gestação e sugerir um algoritmo de tratamento multidisciplinar. A terapia nutricional é a primeira opção de tratamento para as gestantes, e a prática de exercício físico leve a moderado deve ser estimulada na ausência de contraindicações obstétricas. O tratamento medicamentoso está recomendado quando os alvos glicêmicos não são atingidos ou na presença de crescimento fetal excessivo à ultrassonografia. O tratamento tradicional do diabetes gestacional é a insulinoterapia, embora mais recentemente a metformina venha sendo considerada uma opção segura e eficaz. A monitorização do tratamento é realizada com aferição da glicemia capilar e com avaliação da circunferência abdominal fetal por meio de ultrassonografia obstétrica a partir da 28ª semana de gestação.

Obesity and gestational diabetes

The prevalence of both obesity and gestational diabetes mellitus (GDM) is increasing worldwide. GDM affects about 7% of all pregnancies and is defined as any degree of impaired glucose tolerance during gestation. The presence of obesity has a significant impact on both maternal and fetal complications associated with GDM. These complications can be addressed, at least in part, by good glycaemic control during pregnancy. The significance and impact of obesity in women with GDM are discussed in this article, together with treatment options, the need for long-term risk modification and postpartum follow-up.

Prevention of gestational diabetes mellitus: a review of studies on weight management

Entering pregnancy with overweight, obesity or gaining excessive gestational weight could increase the risk of gestational diabetes mellitus (GDM), which is associated with negative consequences for both the mother and the offspring. The objective of this article was to review scientific evidence regarding the association between obesity and GDM, and how weight management through nutritional prevention strategies could prove successful in reducing the risk for GDM. Studies published between January 1975 and January 2009 on the relationship between GDM, pre-pregnancy body mass index (BMI), gestational weight gain and nutritional prevention strategies were included in this review. Results from these reports suggest that maternal obesity assessed by pre-pregnancy BMI is associated with an increased risk of GDM. They also show an association between gestational weight gain and increased risk for GDM. Higher dietary fat and lower carbohydrate intakes during pregnancy appear to be associated with a higher risk for GDM, independent of pre-pregnancy BMI. Some studies showed that restricting energy and carbohydrates could minimize gestational weight gain. However, a firm conclusion on the most effective nutritional intervention for the control of gestational weight gain and glycaemic responses could not be reached based on available studies. In light of the studies reviewed, we conclude that weight management through nutritional prevention strategies could be successful in reducing the risk of GDM. Further studies are required to identify the most effective diet composition to prevent GDM and excessive gestational weight gain.

Management of gestational diabetes mellitus

The incidence of gestational diabetes mellitus (GDM) is on the increase and, if not diagnosed, managed and treated adequately, can have unfavorable maternal and fetal outcomes. Several studies have shown that glycemic values considered as adequate in the past when monitoring GDM failed to contain these adverse outcomes and randomized trials are needed to ascertain whether these targets should be lowered. Dietary restrictions remain the mainstay of GDM management and suitable physical exercise can help too. The use of rapid-acting insulin analogues (lispro and aspart) are novel treatments for improving metabolic control by reducing postprandial glycemia, while long-acting insulin analogues need to be evaluated by further studies for safety in clinical use before they can be prescribed. Numerous studies have found glyburide and metformin safe in women with GDM but more randomized controlled trials are needed, with a long-term follow-up of mother and child, to confirm these results.

Medical nutrition therapy and lifestyle interventions

Nutrient intake plays a significant role in the health outcomes of all pregnant women. In a pregnancy complicated by gestational diabetes mellitus (GDM), excellent glucose control is as foundational as appropriate weight gain and adequate nutrient intake. The controversies in GDM management include the following: how far to manipulate energy intake, dietary composition (carbohydrates and fats), and gestational weight gain. Signs that food restrictions have gone too far include weight loss or lack of weight gain, undereating to avoid insulin therapy, positive urinary ketones, and intentional restriction of healthy foods. If a balance between nutrient needs and glucose control cannot be achieved, then concurrent medication therapy is needed to assist in reducing insulin resistance and supplementing insulin production to provide normoglycemia and improved pregnancy outcomes. Medical nutrition therapy is a self-management therapy. Education, support, and follow-up are required to assist the woman to make lifestyle changes essential to successful nutrition therapy. Women with GDM are at increased risk for type 2 diabetes; learning to manage GDM with lifestyle change provides an opportunity to affect personal risk factors and the health of the whole family.

Maternal obesity, metabolism, and pregnancy outcomes

About one third of all pregnant women in the United States are obese. Maternal obesity at conception alters gestational metabolic adjustments and affects placental, embryonic, and fetal growth and development. Neural tube defects and other developmental anomalies are more common in infants born to obese women; these defects have been linked to poor glycemic control. Preeclampsia, a gestational disorder occurring more frequently in obese women, appears to be due to a subclinical inflammatory state that impairs early placentation and development of its blood supply. Fetal growth and development during the last half of pregnancy depends on maternal metabolic adjustments dictated by placental hormones and the subsequent oxygen and nutrient supply. Maternal obesity affects these metabolic adjustments as well. Basal metabolic rates are significantly higher in obese women, and maternal fat gain is lower, possibly in response to altered leptin function. The usual increase in insulin resistance seen in late pregnancy is enhanced in obese mothers, causing marked postprandial increases in glucose, lipids, and amino acids and excessive fetal exposure to fuel sources, which in turn increases fetal size, fat stores, and risk for disease postnatally. Impaired glucose tolerance, gestational diabetes, and hyperlipidemia are more common among obese mothers. To date, little attention has been given to the role of diet among obese women in preventing these problems. However, studies of women with impaired glucose tolerance show that replacing refined carbohydrates and saturated fat with complex, low-glycemic carbohydrates and polyunsaturated fatty acids improves metabolic homeostasis and pregnancy outcomes. Thus, current dietary guidelines regarding the amount and type of carbohydrates and fat for nonpregnant women seem appropriate for pregnant women as well.

Gestational weight gain and pregnancy outcomes in 481 obese glucose-tolerant women

OBJECTIVE

To investigate the effect of gestational weight gain in obese glucose-tolerant women.

RESEARCH DESIGN AND METHODS

We performed a historical cohort study of 481 women with prepregnancy BMI > or = 30 kg/m2 and a normal 2-h 75-g oral glucose tolerance test (OGTT) during the third trimester (according to World Health Organization criteria). Data on OGTT results and clinical outcomes were collected from medical records. Four groups were defined according to weight gain: group 1, <5.0 kg (n = 93); group 2, 5.0-9.9 kg (n = 134); group 3, 10.0-14.9 kg (n = 132); and group 4, > or = 15.0 kg (n = 122).

RESULTS

Birth weight increased significantly with increasing weight gain (mean grams +/- SD): group 1, 3,456 +/- 620; group 2, 3,624 +/- 675; group 3, 3,757 +/- 582; and group 4, 3,784 +/- 597 (P < 0.001). The birth weight in group 1 was similar to that of the background population of primarily normal-weight women (3,478 g). In multivariate analyses, increasing weight gain was associated with significantly higher rates of hypertension (OR 4.8 [95% CI for group 4 vs. group 1: 1.7-13.1]), cesarean section (3.5 [1.6-7.8]), induction of labor (3.7 [1.7-8.0]), and large-for-gestational-age infants (4.7 [2.0-11.0]). There was no difference in rates of small-for-gestational-age infants. Significant predictors for birth weight (determined by multiple linear regression) were gestational weight gain, 2-h OGTT result, pre-gestational BMI, maternal age, gestational age, and smoking.

CONCLUSIONS

Increasing weight gain in obese women is associated with increasing pregnancy complications. Our data suggest that minimal gestational weight gain might normalize birth weight. Prospective studies should be performed to clarify the safety of recommending limited gestational weight gain.

Gestational diabetes and nutritional recommendations

The goals of medical nutrition therapy for gestational diabetes mellitus (GDM) are to meet the maternal and fetal nutritional needs, as well as to achieve and maintain optimal glycemic control. Nutrition requirements during pregnancy are similar for women with and without GDM. The American Diabetes Association and the American College of Obstetrics and Gynecology recommend nutrition therapy for GDM that emphasizes food choices to promote appropriate weight gain and normoglycemia without ketonuria, and moderate energy restriction for obese women. Current controversies in GDM nutrition therapy involve manipulation of dietary composition (amounts and types of carbohydrates and fats), gestational weight gain, and energy and carbohydrate restriction. Randomized controlled trials are needed to determine which dietary compositions and patterns promote normoglycemia as well as optimal maternal and infant outcomes. Until better evidence is available, nutrition therapy will remain a cornerstone of GDM management with potential benefits that cannot be fully realized in clinical practice.

Maternal obesity not maternal glucose values correlates best with high rates of fetal macrosomia in pregnancies complicated by gestational diabetes

AIM

The current therapeutic strategies to reduce macrosomia rates in gestational diabetes (GDM) have focused on the normalizing of maternal glucose levels. The aim of our study was 1.) to compare maternal glycemic values with the presence of fetal macrosomia at different gestational ages (GA) and with LGA at birth in a cohort of women with glucose intolerance and standard diabetic therapy.

METHODS

306 women with GDM and 97 with impaired glucose tolerance underwent ultrasound examinations at entry and, after initiation of therapy, monthly in addition to standard diabetic therapy. Measurements from the entry diagnostic oGTT, glucose profile and HbA1c and from subsequent glucose profiles obtained within 3 days of the ultrasound at 5 categories of GA age (20-23, 24-27 etc) were retrospectively compared between pregnancies with and without fetal macrosomia, defined as an abdominal circumference (AC) > or = 90th percentile. Maternal prepregnancy BMI was adjusted for and BMI > or = 30 kg/m2 was defined as obesity.

RESULTS

At entry, neither the hourly oGTT values, HbA1c, nor the entry glucose profile differed significantly between pregnancies with and without fetal macrosomia. In a total of 919 pairs of ultrasound/glucose profiles there was no significant difference in glucose levels at every GA category neither in lean nor in obese woman except for the fasting glucose of 32-35 GA. The fetal macrosomia rate in each GA category and the rate of LGA were significantly higher in obese women: e.g. 14.5 vs 28% at diagnosis, 15.7 vs 26.7% at 32-35 weeks, 15.5 vs 25.0% at birth (p < 0.05 for each comparison).

CONCLUSION

The association of maternal glucose values and fetal macrosomia was limited to the fasting glucose values between 32-35 weeks while maternal obesity appeared to be a strong risk factor for macrosomia throughout pregnancies with GDM. In obese women the high fetal macrosomia rate did not appear be normalized by therapy based on maternal euglycemia.

The principles of dietary management of gestational diabetes: reflection on current evidence

BACKGROUND

Gestational diabetes (GDM) is the commonest metabolic disorder of pregnancy. Most women with GDM are treated with nutritional management alone. There are conflicting guidelines surrounding its dietary management and this has resulted in a lack of conformity to the dietary advice currently prescribed. There is also conflicting opinions to the effectiveness of dietary management of GDM on pregnancy outcomes. The aim of this review was to examine the scientific evidence for the optimal nutritional management of GDM.

METHODS

A Medline search of all English papers published between 1995 and 2001 that cross-referenced GDM with diet was under taken. Because of the poor quality of many of these papers, literature prior to 1995 known to the authors and considered relevant to the review were also included.

RESULTS

The evidence base in this area is of poor quality. One systematic review based on randomized control trials failed to show any benefit from dietary intervention in GDM. However, that review did not include informative clinical and observational studies that are not classified as randomized controlled trials. Overall current evidence points to the effectiveness of dietary advice as a means of improving maternal hyperglycaemia and reducing the risk of accelerated foetal growth. The evidence surrounding energy restriction, carbohydrate and fat manipulation in GDM remains controversial.

CONCLUSIONS

Current but limited evidence supports dietary alterations to reduce rates of accelerated foetal growth. There is a clear need for good quality randomized control trials in this area.

Diabetes complicating pregnancy

Despite the well-documented relationship between morbidity in pregnancy and pregestational maternal diabetes, the corrected perinatal outcome is, in most series, equal to or better than that of the general reference obstetric population. No single aspect or element of contemporary management is responsible for this improvement; rather, a combination of interventions seems responsible. Targeting delivery early in term, improved compliance, better glycemic control during pregnancy, improved control at conception, improved neonatal care, family planning, and early screening for fetal abnormalities all likely contribute to improved outcome. The currently observed rates of perinatal mortality suggest that an irreducible minimum mortality rate may be reached; however, large disparities in access to care and treatment continue to result in a wide range in rates of morbidity and mortality, a fact that pertains to outcomes in general as well as to pregnancies complicated by diabetes. The identification of women with lesser degrees of hyperglycemia as diabetic by lowering the thresholds for glucose tolerance test abnormality suggests an importance of the diagnosis that is not supported by evidence of either related morbidity or therapeutic benefit. The extrapolation of risk to women with lesser degrees of hyperglycemia seems to have little basis, and the management of women with mild glucose intolerance as if they had overt diabetes is unwarranted. The excess of resources dedicated to the identification and monitoring of an increasing number of women with mild abnormalities of glucose metabolism should prompt a reevaluation of these practices. Perinatal benefits of this expenditure are difficult to document or nonexistent, and there is a predictable increase in iatrogenic morbidities associated with the diagnosis. The exception in the most recent recommendations is the addition of a random glucose measure to screen for the rare women with overt undiagnosed diabetes who presents for prenatal care, because these women are at increased risk of morbidities related to diabetes. A curious statement was made in the summary and recommendations of the fourth International Congress on Gestational Diabetes: "There remains a compelling need to develop diagnostic criteria for GDM [gestational diabetes mellitus] that are based on the specific relationships between hyperglycemia and risk of adverse outcome." If these relationships are undefined, what is the import of the diagnosis? At the author's center, application of the new diagnostic thresholds for the diagnosis of gestational diabetes mellitus has increased the incidence to over 6%. Without a clear expectation of benefit, this increase represents an unsupportable investment of resources. What are the prospects for improving understanding of the relationships between glucose intolerance and pregnancy risks? The direction of new guidelines and recommendations seems to be moving away from resolution of the relationships. The new criteria result in the diagnosis of gestational diabetes in an increasing number of women who were previously normal. It is easier to differentiate women at an extreme of hyperglycemia from normal. Investigations will be even less able to identify attributable effects of glucose intolerance in pregnancy with the inclusion of women with lesser degrees of hyperglycemia. As evidenced in O'Sullivan's original series, women with fasting hyperglycemia in pregnancy are still presumed to be at increased risk of fetal death. This risk factor remains important in clinical management if insulin treatment, fetal surveillance, and early term delivery can reduce the risk of fetal loss. At the author's center, the relationships among outpatient measures of fasting glycemia, glucose tolerance testing results, and perinatal outcomes are evaluated. Preliminary results suggest that fasting glycemia measured at the time of a 50-g glucose tolerance test is significantly correlated with and as sensitive and predictive of morbidity as the glucose tolerance test diagnosis of gestational diabetes. If these results are confirmed, it will be difficult to rationalize continued glucose tolerance testing.

Higher carbohydrate intake is associated with decreased incidence of newborn macrosomia in women with gestational diabetes

OBJECTIVE

To study the influence of energy and macronutrient intake on infant birthweight in women with gestational diabetes mellitus undergoing intensive management.

DESIGN

This prospective study evaluated the impact of intensive management of gestational diabetes on maternal and fetal morbidity, and addressed the relationship between food intake and infant birthweight.

SETTING

Fifteen maternity hospitals in northern France.

SUBJECTS

Ninety-nine women with gestational diabetes or gestational mild hyperglycemia diagnosed between 24 and 34 weeks of gestation were surveyed. After 1 was excluded because of a premature birth and 18 were excluded as underreporters, 80 women were included in the final analysis. Diet intake was assessed by a dietary history at the first interview, and by two 3-day diet records at the 3rd and 7th week after diagnosis.

RESULTS

In a forward-stepwise regression analysis (controlling for maternal age; smoking; parity; prepregnancy BMI; pregnancy weight gain; gestational duration; infant sex; fasting and 2-hour postprandial serum glucose; insulin therapy; and energy, fat, protein and carbohydrate intake during treatment) infant birthweight was positively associated with gestational duration (beta = +0.34, P<.002), and negatively with smoking (beta = -0.27, P<.02) and carbohydrate intake (beta = -0.24, P<.03). There were no large-for-gestational-age infants among women whose carbohydrate intake exceeded 210 g/day.

CONCLUSION

For women with gestational diabetes undergoing intensive management, higher carbohydrate intake is associated with decreased incidence of macrosomia.

APPLICATION

These findings suggest that nutrition counseling in gestational diabetes must be directed to maintain a sufficient carbohydrate intake (at least 250 g per day), which implies a low-fat diet to limit energy intake. A careful distribution of carbohydrate throughout the day and the use of low-glycemic index foods may help limit postprandial hyperglycemia.

The impact of maternal ketonuria on fetal test results in the setting of postterm pregnancy

OBJECTIVE

The aim of this study was to determine whether ketonuria, a commonly assessed urinary marker of maternal starvation and dehydration, is associated with abnormal fetal test results in the setting of postterm pregnancy.

STUDY DESIGN

During a 4-year period (January 1993-December 1996), a total of 3655 visits for antepartum maternal-fetal testing of postterm pregnancies (> or =41 weeks' gestation) occurred at our institution. Maternal assessment included vital signs and urinalysis. The presence and degree of maternal ketonuria was correlated against abnormal results of fetal heart rate tests, nonstress tests, amniotic fluid index measurements, and biophysical profile scores performed on the same day.

RESULTS

There were 3601 encounters suitable for inclusion in the study. Clinically detectable ketonuria occurred in 10.9% of the patients studied. Patients with clinically detectable ketonuria were at increased risk relative to patients without ketonuria for abnormal outcomes during postterm testing, including the presence of oligohydramnios (24% vs. 9.3%; P<.0001 ), nonreactive nonstress tests (6.2% vs. 2.15%; P<.0001), and fetal heart rate decelerations (14% vs 9.2%; P =.0039 ).

CONCLUSION

Maternal ketonuria among patients with postterm pregnancy was associated with a >2-fold increase in the occurrence of oligohydramnios, a 3-fold increase in nonreactive nonstress tests, and a significant increase in fetal heart rate decelerations. Further studies are required to evaluate the potential benefits of treating ketonuria before fetal testing.

A randomised controlled trial of dietary energy restriction in the management of obese women with gestational diabetes

A randomised controlled trial was designed to determine the effect of moderate 30% maternal dietary energy restriction on the requirement for maternal insulin therapy and the incidence of macrosomia in gestational diabetes. Although the control group restricted their intake to a level similar to that of the intervention group (6,845 kiloJoules (kJ) versus 6,579 kJ), the resulting cohort could not identify any adverse effect of energy restriction in pregnancy. Energy restriction did not alter the frequency of insulin therapy (17.5% in the intervention group and 16.9% in the control group). Mean birthweight (3,461 g in the intervention group and 3,267 g in the control group) was not affected. There was a trend in the intervention group towards later gestational age at commencement of insulin therapy (33 weeks versus 31 weeks) and lower maximum daily insulin dose (23 units versus 60 units) which did not reach statistical significance. Energy restriction did not cause an increase in ketonemia.

Carbohydrate and lipid metabolism in pregnancy: normal compared with gestational diabetes mellitus

This article reviews maternal metabolic strategies for accommodating fetal nutrient requirements in normal pregnancy and in gestational diabetes mellitus (GDM). Pregnancy is characterized by a progressive increase in nutrient-stimulated insulin responses despite an only minor deterioration in glucose tolerance, consistent with progressive insulin resistance. The hyperinsulinemic-euglycemic glucose clamp technique and intravenous-glucose-tolerance test have indicated that insulin action in late normal pregnancy is 50-70% lower than in nonpregnant women. Metabolic adaptations do not fully compensate in GDM and glucose intolerance ensues. GDM may reflect a predisposition to type 2 diabetes or may be an extreme manifestation of metabolic alterations that normally occur in pregnancy. In normal pregnant women, basal endogenous hepatic glucose production (R(a)) was shown to increase by 16-30% to meet the increasing needs of the placenta and fetus. Total gluconeogenesis is increased in late gestation, although the fractional contribution of total gluconeogenesis to R(a), quantified from (2)H enrichment on carbon 5 of glucose (65-85%), does not differ in pregnant women after a 16-h fast. Endogenous hepatic glucose production was shown to remain sensitive to increased insulin concentration in normal pregnancy (96% suppression), but is less sensitive in GDM (80%). Commensurate with the increased rate of glucose appearance, an increased contribution of carbohydrate to oxidative metabolism has been observed in late pregnancy compared with pregravid states. The 24-h respiratory quotient is significantly higher in late pregnancy than postpartum. Recent advances in carbohydrate metabolism during pregnancy suggest that preventive measures should be aimed at improving insulin sensitivity in women predisposed to GDM. Further research is needed to elucidate the mechanisms and consequences of alterations in lipid metabolism during pregnancy.

Gestational diabetes

OBJECTIVE

To review the detection, diagnosis, and clinical management of gestational diabetes.

DATA SOURCES

MEDLINE, Gestational Diabetes Guideline Review, 1968-1998.

STUDY SELECTION

By the author.

DATA EXTRACTION

By the author.

DATA SYNTHESIS

Gestational diabetes is a common complication of pregnancy, occurring in 2% to 6% of pregnancies. Uncontrolled gestational diabetes is associated with increased infant morbidity and mortality, macrosomia, and cesarean deliveries, and is a strong marker for the future development of maternal diabetes mellitus. Women with risk factors for gestational diabetes should be screened for glucose intolerance at 24 to 28 weeks' gestation. If a screening plasma glucose concentration is 140 mg/dL or greater one hour after a 50 gram oral glucose load, then a diagnostic 100 gram, three-hour oral glucose tolerance test should be performed. Medical nutrition therapy is the cornerstone of management and must be designed to meet individual needs. Self-monitoring of blood glucose should be taught to and performed by all women with gestational diabetes. Insulin, which does not readily cross the placental barrier, is the drug therapy of choice in women failing medical nutrition therapy.

CONCLUSION

Pharmacists can optimize overall care by educating, monitoring, and intervening or assisting the patient in the management of gestational diabetes.

Lifestyle modifications for diabetes management

Nutrition therapy and physical activity can assist persons with diabetes to achieve metabolic goals. Several lifestyle strategies can be used. Monitoring metabolic parameters, including blood glucose, glycated hemoglobin, lipids, blood pressure, and body weight, as well as assessing for quality of life are essential to determine whether treatment goals are being achieved by lifestyle changes. If not, adjustments in the overall management plan need to be made.

Metabolic response to meal eating and extended overnight fast in twin gestation

OBJECTIVE

Our purpose was to compare the metabolic response to normal meal eating and the vulnerability to starvation ketosis in twin versus singleton gestation.

STUDY DESIGN

Data are reported on 10 twin and 10 singleton nondiabetic gestations enrolled in a 40-hour metabolic study. Singletons were age (+/- 5 years) and prepregnancy weight (+/- 10% ideal body weight) matched with twins. The diet (35 kcal/kg ideal body weight for singletons, 40 kcal/kg ideal body weight for twins) was distributed as one fifth at 8 AM, two fifths at 1 PM, and two fifths at 6 PM. An overnight fast was extended until noon the following day. Glucose and beta-hydroxybutyrate measurements were made hourly except at night, when they were made every 2 hours. Insulin values were obtained before and after dinner and on the day when breakfast was delayed.

RESULTS

The glucose, beta-hydroxybutyrate, and insulin excursions in response to meal eating from 8 AM to 12:00 noon on day 1 were similar in twin and singleton pregnancies (analysis of variance for repeated measures, p < 0.05). On day 2, when breakfast was delayed, a progressive decrement in glucose was observed in both twins and singletons (p = 0.4682). Concurrently, there was a progressive rise in beta-hydroxybutyrate in both twins and singletons, which was significantly greater for twins compared with singletons (p = 0.002).

CONCLUSIONS

These data indicate that twin gestations are more vulnerable to the accelerated starvation of late normal pregnancy than singletons are in spite of additional caloric intake. We speculate that the observed difference may be the result of the increased metabolic demands of twin gestation.

The role of the placenta in fetal nutrition and growth

The placenta plays a key role in the nutrition of the fetus. It mediates the active transport of nutrients and metabolic wastes across the barrier separating maternal and fetal compartments, as well as modifying the composition of some nutrients through its own metabolic activity. The function of the placenta is essential to the growth of a healthy fetus; it is becoming apparent that the activities of the placenta are in turn modulated by signals originating from the fetus. Communication between placenta and fetus is especially critical in intrauterine growth retardation. The importance of the interaction of factors like insulin-like growth factor and epidermal growth factor with their receptors is becoming increasingly clear.