Energy requirements of pregnancy in The Netherlands

The relationship between pre-pregnancy BMI and energy and macronutrients intakes during pregnancy in women from Yucatan, Mexico

In this observational study, our aim was to analyse the association between pre-pregnancy BMI and adequacy rates of energy and macronutrient intakes in a sample of pregnant women from Yucatan, Mexico. From September to December 2019, we collected data on socioeconomic, pregnancy, and dietary characteristics, and took anthropometric measurements of women during household visits. Pre-pregnancy BMI was calculated from measured height and self-reported body weight. Energy and macronutrient intakes (obtained from three 24-h dietary recalls) were compared with the estimated trimester-specific requirements to calculate adequacies (%). Multiple linear regression models showed that after accounting for maternal socioeconomic characteristics and perinatal variables, each unit increase in pre-pregnancy BMI was associated with decreases of 2%, 2%, and 2.6% in energy, carbohydrate, and total fat intakes, respectively. These results were significant when under- and over-reporters were excluded from the analyses. Women who enter pregnancy with higher BMI values may voluntarily or involuntarily reduce their food intake.IMPACT STATEMENTWhat is already know about this subject? Some studies have analysed the relationship between pre-pregnancy BMI categories (normal weight, overweight, and obesity) and diet quality during pregnancy, but few studies have focussed on quantitative energy and macronutrient intakes or their adequacies in relation to pre-pregnancy BMI.What do the results of this study contribute? In this sample of Mexican women belonging to a middle socioeconomic status, we found that after excluding under- and over-reporters from the analyses and accounting for maternal socioeconomic characteristics and perinatal variables, BMI was negatively associated with adequacy intake rates of energy, carbohydrates, and total fats during pregnancy.What are the implications of these findings for clinical practice and/or further research? Women who enter pregnancy with higher BMI values may voluntarily or involuntarily reduce their food intake. These results can be used to accordingly plan diet counselling during pregnancy.

Energy expenditure during pregnancy: a systematic review

CONTEXT

Contrary to nutritional guidelines, accumulating evidence shows that pregnant women's energy intakes remain stable throughout trimesters. Although pregnant women may eat below their needs or underreport their energy intakes, it is also relevant to question how energy requirements - estimated through measurements of energy expenditure (EE) - change throughout pregnancy.

OBJECTIVE

This review examined prospective studies that measured EE during pregnancy, following the Preferred Reporting Items for Systematic Reviews and Meta-Analyses guidelines.

DATA SOURCES

PubMed/MEDLINE, Web of Science, Embase, and CINAHL databases were searched to identify relevant publications up to November 14, 2019.

STUDY SELECTION

All studies that measured EE prospectively and objectively during pregnancy were included in this systematic review. Two authors independently screened 4852 references. A total of 32 studies were included in the final analysis.

DATA EXTRACTION

One author extracted data and assessed the risk of bias and a second author did so for a random sample of studies (n = 7; 22%).

DATA ANALYSIS

Increases in resting EE ranged from 0.5% to 18.3% (8-239 kcal), from 3.0% to 24.1% (45-327 kcal), and from 6.4% to 29.6% (93-416 kcal) between early and mid-, mid- and late, and early and late pregnancy, respectively. Increases in total EE ranged from 4.0% to 17.7% (84-363 kcal), from 0.2% to 30.2% (5-694 kcal), and from 7.9% to 33.2% (179-682 kcal) between early and mid-, mid- and late, and early and late pregnancy, respectively. Participants were mainly of normal weight, although many studies did not report important covariates such as prepregnancy body mass index and gestational weight gain adequacy.

CONCLUSIONS

Additional high-quality longitudinal studies (ie, with multiple objective measurements of EE in all periods of pregnancy while considering important confounding variables, like gestational weight gain) are required.

National guidelines on nutrient reference values for the healthy adult population and for pregnant or lactating women are based on heterogeneous sources of evidence: review of guidelines

Many countries provide dietary guidelines for health practitioners and/or the general population. However, there is no general, international guideline serving as a template for national dietary guidelines, and there is little to no consensus regarding reference values for different nutrients. The present review compared 27 national dietary guidelines for healthy adults as well as for pregnant and/or breastfeeding women, and analysed their quality and the evidence behind their recommendations. The guidelines were evaluated for their quality using the instrument Agree II, and found to be heterogeneous (overall quality score 14%-100%) and often insufficient (quality score < 50%) due to missing information about their methodology and sources of evidence. We analysed the evidence (number of studies, study types and publication years) of reference values of a number of nutrients using the five guidelines that provided the highest scores in the Agree II assessment. The reference values varied among guidelines, were rarely based on up-to-date meta-analyses, and were often based on insufficiently reported evidence (22/27 guidelines with quality score < 50%). We recommend systematic reviews of high quality studies to formulate future guidelines, and to use guidelines on how to write guidelines.

Thyroid dysfunction in Iranian pregnant women: a systematic review and meta-analysis

BACKGROUND

Thyroid dysfunction during pregnancy is associated with adverse outcomes for both mother and fetus. The present meta-analysis was conducted to evaluate thyroid dysfunction in Iranian pregnant women.

METHODS

We registered this review at PROSPERO (registration number: CRD42020166655). The research steps in this systematic review and meta-analysis were performed according to the MOOSE protocol, and finally, reports were provided based on the PRISMA guidelines. The literature search was performed in October 2019 using the international online databases, including Web of Science, Ovid, Science Direct, Scopus, EMBASE, PubMed/Medline, Cochrane Library, EBSCO, CINAHL, Google Scholar as well as national databases were reviewed. Data were extracted after applying the inclusion and exclusion criteria and qualitative evaluation of the studies. I2 index and Q test were used to assess differences in studies. All analyses were performed using Comprehensive Meta-Analysis Software. P-value less than 0.05 was considered statistically significant. We identified 1261 potential articles from the databases, and 426 articles remained after removing the duplicate and unrelated studies. After evaluating the full text, 52 articles were removed.

RESULTS

Finally, 19 eligible studies including 17,670 pregnant women included for meta-analysis. The prevalence of thyroid dysfunction in Iranian pregnant women was 18.10% (95%CI: 13.89-23.25). The prevalence of hypothyroidism, clinical hypothyroidism, and subclinical hypothyroidism in Iranian pregnant women was respectively estimated to be 13.01% (95%CI: 9.15-18.17), 1.35% (95%CI: 0.97-1.86) and 11.90% (95%CI: 7.40-18.57). The prevalence of hyperthyroidism, clinical hyperthyroidism, and subclinical hyperthyroidism in Iranian pregnant women was respectively estimated to be 3.31% (95%CI: 1.62-6.61), 1.06% (95%CI: 0.61-1.84) and 2.56% (95%CI: 0.90-7.05). The prevalence of anti-thyroperoxidase antibody was estimated to be 11.68% (95%CI: 7.92-16.89).

CONCLUSION

The results of this meta-analysis showed a high prevalence of thyroid disorders, especially hypothyroidism. The decision to recommend thyroid screening during pregnancy for all women is still under debate, because the positive effects of treatment on pregnancy outcomes must be ensured. On the other hand, evidence about the effect of thyroid screening and treatment of thyroid disorders on pregnancy outcomes is still insufficient. Nevertheless, a large percentage of general practitioners, obstetricians and gynecologists perform screening procedures in Iran.

Pregnancy and lactation, a challenge for the skeleton

In this review we discuss skeletal adaptations to the demanding situation of pregnancy and lactation. Calcium demands are increased during pregnancy and lactation, and this is effectuated by a complex series of hormonal changes. The changes in bone structure at the tissue and whole bone level observed during pregnancy and lactation appear to largely recover over time. The magnitude of the changes observed during lactation may relate to the volume and duration of breastfeeding and return to regular menses. Studies examining long-term consequences of pregnancy and lactation suggest that there are small, site-specific benefits to bone density and that bone geometry may also be affected. Pregnancy- and lactation-induced osteoporosis (PLO) is a rare disease for which the pathophysiological mechanism is as yet incompletely known; here, we discuss and speculate on the possible roles of genetics, oxytocin, sympathetic tone and bone marrow fat. Finally, we discuss fracture healing during pregnancy and lactation and the effects of estrogen on this process.

A life history approach to prenatal supplementation: Building a bridge from biological anthropology to public health and nutrition

While prenatal supplementation with protein, lipids, carbohydrates, and micronutrients has been used to improve infant outcomes in undernourished populations since the 1960s with inconsistent results, a flourishing body of literature within biological anthropology has used life history theory to explain why supplemental resources are often allocated to maternal survival and future reproduction and not to the current offspring. To date, however, public health and nutrition researchers have not adopted evolutionary perspectives in designing or analyzing prenatal supplementation studies. The result is a long series of supplementation trials with unpredictable and often disappointing outcomes for women and children, as well as serious lacunae in the understanding of long-term consequences of supplementation for women. The goal of this article is to open a tactical conversation about how to build a bridge between the evolutionary logic of biological anthropology and the evidentiary standards and methods of public health and nutrition with the aim of advancing knowledge about reproductive and metabolic physiology and improving women's health over the life course. The article reviews recent prenatal supplementation studies and proposes programmatic strategies by which biological anthropologists and public health and nutrition workers may collaborate to define different conditions of prenatal supplement resource allocation and to target more effective interventions.

Cognitive costs of reproduction: life-history trade-offs explain cognitive decline during pregnancy in women

Life-history theory predicts that access to limited resources leads to trade-offs between competing body functions. Women, who face higher costs of reproduction when compared to men, should be especially vulnerable to these trade-offs. We propose the 'cognitive costs of reproduction hypothesis', which states that energy trade-offs imposed by reproduction may lead to a decline in maternal cognitive function during gestation. In particular, we hypothesize that the decline in cognitive function frequently observed during pregnancy is associated with the allocation of resources between the competing energetic requirements of the mother's brain and the developing foetus. Several distinctive anatomical and physiological features including a high metabolic rate of the brain, large infant size, specific anatomical features of the placenta and trophoblast, and the lack of maternal control over glucose flow through the placenta make the occurrence of these trade-offs likely. Herein, we review several lines of evidence for trade-offs between gestation and cognition that are related to: (i) energy metabolism during reproduction; (ii) energy metabolism of the human brain; (iii) links between energy metabolism and cognitive function; and (iv) links between gestation and cognitive function. We also review evidence for the important roles of cortisol, corticotropin-releasing hormone and sex hormones in mediating the effects of gestation on cognition, and we discuss possible neurophysiological mechanisms underlying the observed effects. The evidence supports the view that energy trade-offs between foetal growth and maternal endocrine and brain function lead to changes in maternal cognition, and that this phenomenon is mediated by neuroendocrine mechanisms involving the hypothalamic-pituitary-adrenal axis, brainstem nucleus locus coeruleus and hippocampus.

Assessment of resting energy expenditure and body composition in Japanese pregnant women with diabetes

AIMS/INTRODUCTION

To measure longitudinal changes in resting energy expenditure and body composition of Japanese pregnant women with or without diabetes.

MATERIALS AND METHODS

The study population consisted of women who had delivered a live singleton neonate after 22 weeks' gestation at Okayama University Hospital from July 2013 to June 2017. Resting energy expenditure and body composition were measured in the first trimester, second trimester, third trimester and postpartum.

RESULTS

A total of 144 women participated in this study: 103 with normal glucose tolerance and 41 with diabetes. The resting energy expenditure (kcal/day) of pregnant women with normal glucose tolerance was significantly higher in the third trimester (1,644 ± 234) than in the first (1,461 ± 215) and second trimesters (1,491 ± 219), and postpartum (1,419 ± 254), whereas that of pregnant women with diabetes did not significantly change during all periods (1,568 ± 404, 1,710 ± 332, 1,716 ± 251, 1,567 ± 249). The resting energy expenditure of women with good glycemic control was lower than that of women with poor control. Fat-free mass was closely correlated with resting energy expenditure.

CONCLUSIONS

The resting energy expenditure of Japanese pregnant women with normal glucose tolerance was significantly increased in the third trimester. The resting energy expenditure of women with good glycemic control was lower than that of women with poor control. Resting energy expenditure and fat-free mass are potential indexes for medical nutrition therapy in pregnant women with diabetes.

Reference intervals of trimester-specific thyroid stimulating hormone and free thyroxine in Chinese women established by experimental and statistical methods

BACKGROUND

As a result of physiological and metabolic changes during pregnancy, thyroid hormones can be affected significantly throughout entire three trimesters. According to the guidelines published by American Thyroid Association in 2017, it is strongly recommended to establish population-based trimester-specific and assay method-specific reference intervals (RIs) using local population.

METHODS

A total of 1209 pregnant women without personal or family history of thyroid disease were recruited from July 2015 to April 2017 at Beijing Obstetrics and Gynecology Hospital. Those initially selected patients were further tested for TSH, FT4 and thyroid peroxidase antibody (aTPO), performed on the chemiluminescent platform Siemens ADVIA Centaur^® XP. Only patients tested negative for aTPO were included in reference interval establishment. RIs for both TSH and FT4 were determined as 2.5th percentile to 97.5th percentile on the data distribution.

RESULTS

The TSH and FT4 trimester-specific RIs were as follows: 0.59-3.54 mIU/L, 11.8-18.4 pmol/L (n = 188, 1st trimester); 0.80-4.46 mIU/L, 11.6-17.4 pmol/L (n = 133, 2nd trimester); 0.72-4.19 mIU/L, 9.7-15.1 pmol/L (n = 157, 3rd trimester). The RIs of TSH and FT4 determined by Hoffmann method for first trimester outpatient pregnant women were 0.33-3.96 mIU/L (n = 9924) and 11.7-17.5 pmol/L (n = 10039), respectively.

CONCLUSION

Trimester-specific thyroid function tests RIs are distinct from those provided by assay manufacturers. The RIs determined by direct sampling and Hoffmann indirect calculation showed no statistical difference.

2017 Guidelines of the American Thyroid Association for the Diagnosis and Management of Thyroid Disease During Pregnancy and the Postpartum

BACKGROUND

Thyroid disease in pregnancy is a common clinical problem. Since the guidelines for the management of these disorders by the American Thyroid Association (ATA) were first published in 2011, significant clinical and scientific advances have occurred in the field. The aim of these guidelines is to inform clinicians, patients, researchers, and health policy makers on published evidence relating to the diagnosis and management of thyroid disease in women during pregnancy, preconception, and the postpartum period.

METHODS

The specific clinical questions addressed in these guidelines were based on prior versions of the guidelines, stakeholder input, and input of task force members. Task force panel members were educated on knowledge synthesis methods, including electronic database searching, review and selection of relevant citations, and critical appraisal of selected studies. Published English language articles were eligible for inclusion. The American College of Physicians Guideline Grading System was used for critical appraisal of evidence and grading strength of recommendations. The guideline task force had complete editorial independence from the ATA. Competing interests of guideline task force members were regularly updated, managed, and communicated to the ATA and task force members.

RESULTS

The revised guidelines for the management of thyroid disease in pregnancy include recommendations regarding the interpretation of thyroid function tests in pregnancy, iodine nutrition, thyroid autoantibodies and pregnancy complications, thyroid considerations in infertile women, hypothyroidism in pregnancy, thyrotoxicosis in pregnancy, thyroid nodules and cancer in pregnant women, fetal and neonatal considerations, thyroid disease and lactation, screening for thyroid dysfunction in pregnancy, and directions for future research.

CONCLUSIONS

We have developed evidence-based recommendations to inform clinical decision-making in the management of thyroid disease in pregnant and postpartum women. While all care must be individualized, such recommendations provide, in our opinion, optimal care paradigms for patients with these disorders.

Prevalence of hypothyroidism in pregnancy: An epidemiological study from 11 cities in 9 states of India

BACKGROUND

A previous hospital based study from Delhi revealed a high prevalence of hypothyroidism in pregnant women. Several other studies with small sample size also indicate a rising trend of prevalence of hypothyroidism during pregnancy in India.

OBJECTIVE

To assess prevalence of hypothyroidism in pregnant women from various states/cities across India.

MATERIALS AND METHODS

This was a cross-sectional multicenter study conducted at Allahabad (Uttar Pradesh), Bengaluru (Karnataka), Chennai (Tamil Nadu), Kolkata (West Bengal), Hyderabad (Telangana), Nasik (Maharashtra), Rohtak (Haryana), Pune (Maharashtra), New Delhi (Delhi), Srinagar (Kashmir), and Vizag (Andhra Pradesh) enrolling 2599 pregnant women. Estimation of thyroid stimulating hormone (TSH), free T4, and antithyroid peroxidase (TPO) antibodies was carried out using Roche modular kit using ECLIA technology in a central laboratory.

RESULTS

We found in our study population that 13.13% of pregnant women have hypothyroidism (n = 388), using a cutoff TSH level of 4.5 μIU/ml. This prevalence was much higher using the American Thyroid Association criteria. Anti-TPO antibodies were positive in 20.74% of all pregnant women (n = 613), whereas 40% (n = 155) of hypothyroid pregnant women were positive for anti-TPO antibodies.

CONCLUSION

This study concludes that there is a high prevalence of hypothyroidism (13.13%), majority being subclinical in pregnant women during the first trimester from India and universal screening of hypothyroidism may be desirable in our country.

Subclinical hypothyroidism in pregnancy: An emerging problem in Southern West Bengal: A cross-sectional study

Background:

Prevalence of subclinical hypothyroidism (SCH) in pregnancy varies widely in different parts of our country, but it has multiple adverse outcomes in both the mother and fetus.

Objectives:

This study was conducted to evaluate the prevalence of SCH in pregnant women during the first trimester and to identify the prevalence of thyroid autoimmunity in pregnant women.

Materials and Methods:

This cross-sectional study (March 2014 to February 2015) was conducted among the pregnant women attending antenatal clinic in their first trimester at a tertiary care center. Morning samples of study participants were analyzed for free thyroxin (FT4), thyroid stimulating hormone (TSH), and thyroid peroxidase antibody (TPO Ab). Data expressed as mean ± standard deviation and percentage (%) as applicable.

Results:

Of the 510 subjects, 168 had TSH value >2.5 μIU/ml (32.94%) with normal FT4 and they were diagnosed as SCH. TSH level >4.5 μIU/ml was estimated in 13.92% (71) of the subjects. TPO Ab was positive in 57 (33.93%) of subclinical hypothyroid and 5 (1.47%) of normal subjects. 70.42% (50) of the subjects with TSH >4.5 μIU/ml had positive TPO Ab.

Conclusions:

Prevalence of SCH is high in South Bengal and routine thyroid screening at the first antenatal visit should be done to reduce the social and financial burden caused by SCH.

[Basal metabolism during pregnancy: a systematic review]

Gestational energy expenditure (EE) is the basis for nutritional counseling and body weight control. The objective of this study was to systematically review the behavior of the basal metabolic rate (BMR), the major component of EE, during non gemelar pregnancy of healthy women. Based on the inclusion criteria, 37 articles were identified (24 cohort and 13 cross-sectional studies). Increases in BMR (between 8% and 35%) were observed in most cohort studies and it was related to the duration of follow-up and nutritional status. In the cross-sectionals, the increase in BMR varied from 8% to 28% close to delivery in comparison with the first trimester or post-partum. Lack of information on maternal age, loss of follow-up and short duration of follow-up during the pregnancy were serious limitations in the identified studies. In conclusion, BMR increases during pregnancy, and the increase is more intense after the second trimester. The most reliable data come from the few cohort studies that initiated before pregnancy.

Subcutaneous body fat in pregnant New Zealand women: association with wheeze in their infants at 18 months

To investigate the association of subcutaneous body fat levels in pregnant women with wheezing in their 18 month old infants. A prospective study of European and Polynesian volunteers (n = 369) recruited from northern New Zealand were visited in months 4 and 7 of pregnancy when height, weight, and triceps, biceps and costal skinfolds were measured, and questionnaires determining personal details administered; and again visited 18 months after birth when infants were measured and questions on infant feeding and wheeze administered. At 18 months 32 % of infants had wheezed in the past 12 months. Increased wheeze was associated with maternal asthma, eczema or allergy (p = 0.001); receiving family welfare payments (p = 0.010); and being Polynesian (p = 0.021); while exclusive breastfeeding to 2 months (p = 0.045) was associated with decreased wheeze. Individual month 4 and month 7 mean triceps, biceps and costal skinfolds were all greater in mothers of wheezers compared to nonwheezers, biceps and costal skinfolds significantly so (p = 0.002, p = 0.005 at month 7). The sum of these skinfolds at month 4, at month 7, and the difference between these sums, were all significantly associated with increased risk of infant wheeze at 18 months when considered alone (p = 0.037, p = 0.001 and p = 0.015) or in combination. Prevalence of infant wheeze was 22.7 % for mothers with lower quartile month 7 skinfolds, compared to 45.0 % for mothers with upper quartile. After adjusting for significant covariates the difference in skinfolds had the strongest association (p = 0.003) followed by sum at month 4 (p = 0.074 or 0.003 depending on whether Polynesian ethnicity was included in the model). The sum of skinfolds declined between month 4 and month 7 in 34 % of women. Prevalence of wheeze was 19.2 % where the difference in mothers' skinfolds between month 4 and month 7 decreased by 10 mm or more and 41.7 % where the difference increased by 10 mm or more. Mean month 4 weights, BMI and sum of skinfolds were below average in the latter group. As the sum of month 4 or month 7 maternal skinfolds increased the prevalence of infant wheeze increased. In addition as the change in skinfolds between month 4 and month 7 became more positive the prevalence of infant wheeze increased. This study suggests for the first time that changes in subcutaneous fat during pregnancy are associated with prevalence of infant wheeze.

High prevalence of subclinical hypothyroidism during first trimester of pregnancy in North India

BACKGROUND

Thyroid dysfunction is a common occurrence in pregnancy and affects both maternal and fetal outcomes. There are limited data on prevalence of hypothyroidism during pregnancy from India. Therefore, this study was designed to evaluate the prevalence of thyroid dysfunction especially hypothyroidism during first trimester in a large public hospital in North India.

MATERIALS AND METHODS

All the consecutive first trimester pregnant women attending Lok Nayak and Kasturba Hospitals were enrolled in the study after institutional ethics approval and consent from the study subjects. The pregnant women with diagnosed thyroid disease and on thyroid medications were excluded from the study. Morning samples of study participants were analyzed for thyroid hormone profile which included free T3, free T4, TSH, and TPO Ab. In addition, all study participants were tested for CBC, LFT, KFT, and lipid profile.

RESULTS

A total of 1000 women were enrolled for this prospective observational study. The mean (SD) age of study subjects was 25.6 (11.1) years, and mean (SD) gestational age was 10.3 (3.4) weeks. One hundred and forty-three (14.3%) subjects had TSH values more than 4.5 mIU/L above the cutoff used for definition of hypothyroidism. Out of these, 135 had normal free T4 and therefore labeled as subclinical hypothyroidism and 7 had low free T4 suggestive of overt hypothyroidism. TPO Ab was positive in 68 (6.82%) of total, 25 (18.5%) of subclinical and 5 (71%) of overt hypothyroid patients.

CONCLUSION

Hypothyroidism, especially subclinical, is common in North Indian women during first trimester. Further countrywide studies are needed to evaluate the prevalence and etiology of hypothyroidism to prevent maternal and fetal adverse effects of hypothyroidism in India.

Sex differences in energy metabolism need to be considered with lifestyle modifications in humans

Women have a higher proportion of body fat compared to men. However, women consume fewer kilojoules per kilogram lean mass and burn fat more preferentially during exercise compared with men. During gestation, women store even greater amounts of fat that cannot be solely attributed to increased energy intake. These observations suggest that the relationship between kilojoules consumed and kilojoules utilised is different in men and women. The reason for these sex differences in energy metabolism is not known; however, it may relate to sex steroids, differences in insulin resistance, or metabolic effects of other hormones such as leptin. When considering lifestyle modifications, sex differences in energy metabolism should be considered. Moreover, elucidating the regulatory role of hormones in energy homeostasis is important for understanding the pathogenesis of obesity and perhaps in the future may lead to ways to reduce body fat with less energy restriction.

Correlates of absolute and excessive weight gain during pregnancy

OBJECTIVE

Factors associated with weight gain during pregnancy that may be linked to maternal overweight and obesity were examined.

METHODS

In this observational study, 144 women reported on demographics, (prepregnancy) body weight, and lifestyles in self-reported questionnaires at 30 weeks gestation. Body weight at the end of pregnancy (self-reported at 6 weeks postpartum) was used to determine total gestational weight gain. Multivariate prediction models were developed to identify factors associated with total gestational weight gain and excessive gestational weight gain (i.e., higher weight gain than recommended by the Institute of Medicine).

RESULTS

Women gained 14.4 (+/-5.0) kg during pregnancy. Obese women gained almost 4 kg less than normal weight women. Pregnant women judging themselves to be less physically active or women who reported increased food intakes during pregnancy gained significantly more weight. Over one third of women (38%) gained more weight than recommended. Being overweight, judging yourself to be less physically active than others, and a perceived elevated food intake during pregnancy were significantly associated with excessive weight gain (odds ratio [OR] = 6.33, 95% confidence interval [CI]: 2.01-19.32; OR = 3.96, 95% CI: 1.55l, 10.15; and OR = 3.14, 95% CI: 1.18, 8.36, respectively). A higher age at menarche and hours of sleep reduced the odds for excessive weight gain (OR = 0.75, 95% CI: 0.57, 0.99; and OR = 0.35, 95% CI: 0.57, 0.93, respectively).

CONCLUSIONS

Mean hours of sleep, perceived physical activity, and measures of food intake at 30 weeks gestation were identified as modifiable behavioral correlates for excessive gestational weight gain. Strategies to optimize gestational weight gain need to be explored, with a focus on the identified factors.

Longitudinal analysis of changes in energy intake and macronutrient composition during pregnancy and 6 weeks post-partum

PURPOSE

This prospective study was carried out in order to investigate changes in nutritional intake during pregnancy with regard to caloric intake and macronutrient composition in normal-weight pregnant women.

METHODS

Using food scales, 32 healthy pregnant women estimated their food intake over a period of 2 days at gestational week 16, 22, 30, 36 and, in addition, 6 weeks after delivery. The recorded food logs were analyzed with respect to caloric intake and macronutrient composition.

RESULTS

The women's age was averaged 29.6 ± 4.5 years, and the mean pre-pregnancy BMI was 22.4 ± 2.5 kg/m². Mean weight gain was 16.5 ± 4.5 kg. On average, birth took place during the 40th week of gestation, with the babies having a mean birth weight of 3,515 ± 406 g. Caloric intake during the gestation period and post-partum showed no statistically significant changes and added up 9,237 ± 1,876 kJ/day during the 16th week of gestation, 9,496 ± 2,437 kJ/day during the 22nd, 9,073 ± 1,863 kJ/day during the 30th, 9,525 ± 2,135 kJ/day during the 36th week and 8,445 ± 2,160 kJ/day 6 weeks after delivery. No significant changes were observed in the composition of macronutrients during the pregnancy. The daily composition of macronutrients was as follows: carbohydrates 281 ± 57 g/day (51.7%), fat 86 ± 16 g/day (35.8%) and protein 75 ± 13 g/day (13.9%). However, we observed a decrease in carbohydrate intake of 239 ± 72 g/day (48%) after birth.

CONCLUSIONS

Healthy pregnant women showed no significant changes in their caloric intake or nutritional profiles. Performed with an accurate measurement, this prospective study shows that healthy pregnant require neither increased caloric intake nor a change in macronutrient composition.

A Brief Review on How Pregnancy and Sex Hormones Interfere with Taste and Food Intake

Many physiological and behavioral changes take place during pregnancy, including changes in taste and an increase in food intake. These changes are necessary to ensure growth and development of a healthy fetus. Both hyperphagia and taste changes during pregnancy may be induced by sex hormones estrogen and progesterone that are increased during pregnancy. Indeed, it has been shown that estrogen decreases food intake, while progesterone increases food intake. This is for instance apparent from the fact that food intake changes during the menstrual cycle with variation in sex hormones. This review will give a short overview of the effects of pregnancy and sex hormones on food intake and taste.

Does oestrogen allow women to store fat more efficiently? A biological advantage for fertility and gestation

In normal healthy-weight humans, women have a higher percentage body fat than men, a difference that commences at puberty and continues throughout adult life, suggesting that the mechanism is related to sex steroids. The first half of pregnancy is also a stage of body fat gain in women. From an energy balance point, there is no explanation why women should be fatter than men, as the latter consume more calories proportionately. Moreover, women store fat in early pregnancy when caloric intake does not significantly change. The aim of this review is to focus on evidence supporting one mechanism that may account for these findings. That is, oestrogen reduces postprandial fatty acid oxidation leading to an increase in body fat which may account for the greater fat mass observed in women compared with men and the fat gain in early pregnancy. Therefore, female puberty and early pregnancy could be seen as states of efficient fat storage of energy in preparation for fertility, foetal development and lactation providing an obvious biological advantage. Further research into this mechanism of fat storage may provide further insights into the regulation of body fat.

Do the changes in energy balance that occur during pregnancy predispose parous women to obesity?

The aim of this review was to re-assess whether the changes in energy balance that accompany pregnancy predispose parous women to obesity. A number of cross-sectional studies have sought to answer this question by examining the relationship between parity and maternal body weight. However, these studies were unable to control for the large number of sociobehavioural confounders that might be responsible for the apparent effect of parity on body weight. Longitudinal studies that examine changes in maternal body weight before and after regnancy avoid these problems by using each mother as her own control. Nevertheless, these studies have to overcome three methodological constraints: They must obtain an accurate measure of prepregnant body weight, they must give each mother sufficient time to lose any weight retained following delivery, and they must take into account the effect of ageing on maternal weight gain during pregnancy and the follow-up period. More than 90% of the studies reviewed found body weight to be greater after pregnancy than it was before (by 0.2–10.6kg). and previous researchers who have examined the evidence for pregnancy-related weight gains suggest that body weight increases by an average of 04–4.8kg following pregnancy. However, only three of the 71 longitudinal studies examined in the present review complied with the three methodological criteria. These studies concluded that mothers gain, on average, 0.9–3.3kg more weight following pregnancy than nonpregnant controls, and that mean body weight remained 0.4–3.0kg higher, even after controlling for a number of sociobehavioural confounders. This apparently modest increase in mean maternal body weight for women having one or two children conceals the fact that some mothers experience a substantial increase in body weight and become obese following pregnancy. It remains unclear whether these increases are simply the result of changes in energy metabolism during pregnancy and lactation, or whether they are influenced by inherent changes in lifestyle that accompany pregnancy and motherhood. Understanding the relative importance of these alternatives might help to explain the aetiology of maternal obesity.

“Clover was a stout motherly mare approaching middle life, who had never quite got her figure back after her fourth foal”

George Well (1945) Animal Farm. London: Secker and Warburg.

[A Longitudinal study of body composition and basal metabolic rate during pregnancy in a black population of Kinshasa, Democratic Republic of Congo (RDC)]

OBJECTIVE

A longitudinal study of body composition and basal metabolic rate during pregnancy in a black population of Kinshasa.

MATERIALS AND METHODS

Body composition and basal metabolic rate were determined by bioimpedance, and energy intake was evaluated using the 24 h recall method at 20, 34 and > 37 weeks of gestation in 76 black, Congolese women. The subjects had to be healthy, and to deliver term, singleton infants after a normal pregnancy.

RESULTS

At 20 weeks of pregnancy, the 76 women, aged 28.5+/-6.4 years, had a body weight of 61.1+/-7.7 kg, a body mass index of 23.0+/-3.8 kg/m(2), a fat mass of 36.6+/-6.8% and a basal metabolic rate of 1399+/-84 kcal/24 h. Subsequently, increases in body weight (+6.5 kg), fat-free mass (+ 5.1 kg), body water (+4.4 l) and basal metabolic rate (+297 kcal/24 h) (P < 0.0001) were observed. The increase in fat mass (+1.4 kg) was less pronounced. Energy intake was stable.

CONCLUSION

Changes in body composition during pregnancy in Congolese black women are comparable to those reported in other populations. Pre- and per-gravidic fat mass is higher in congolese women than in Caucasian women.

Energy requirements during pregnancy and lactation

Objective

To estimate the energy requirements of pregnant and lactating women consistent with optimal pregnancy outcome and adequate milk production.

Design

Total energy cost of pregnancy was estimated using the factorial approach from pregnancy-induced increments in basal metabolic rate measured by respiratory calorimetry or from increments in total energy expenditure measured by the doubly labelled water method, plus energy deposition attributed to protein and fat accretion during pregnancy.

Setting

Database on changes in basal metabolic rate and total energy expenditure during pregnancy, and increments in protein based on measurements of total body potassium, and fat derived from multi-compartment body composition models was compiled. Energy requirements during lactation were derived from rates of milk production, energy density of human milk, and energy mobilisation from tissues.

Subjects

Healthy pregnant and lactating women.

Results

The estimated total cost of pregnancy for women with a mean gestational weight gain of 12.0 kg, was 321 or 325 MJ, distributed as 375, 1200, 1950 kJ day-1, for the first, second and third trimesters, respectively. For exclusive breastfeeding, the energy cost of lactation was 2.62 MJ day-1 based on a mean milk production of 749 g day-1, energy density of milk of 2.8 kJ g-1, and energetic efficiency of 0.80. In well-nourished women, this may be subsidised by energy mobilisation from tissues on the order of 0.72 MJ day-1, resulting in a net increment of 1.9 MJ day-1 over non-pregnant, non-lactating energy requirements.

Conclusions

Recommendations for energy intake of pregnant and lactating women should be updated based on recently available data.

Changes in body fat distribution in relation to parity in American women: a covert form of maternal depletion

Using data from the Third National Health and Nutrition Examination Survey (NHANES III), conducted from 1988-1994, we investigated the effect of reproduction on the distribution of body fat in well-nourished American women. While women tend to gain weight and fat with succeeding pregnancies, if age and body mass index are controlled, increasing parity is associated with a decrease in hip and thigh circumferences, suprailiac and thigh skinfolds, and body fat estimated from skinfolds, while waist circumference increases, resulting in a relative decrease in lower-body fat. The mobilization of fat stores in the lower body during late pregnancy and lactation may help to meet the special needs of the developing brain for essential fatty acids and energy during the time of peak growth. When fat is regained after the postpartum period, relatively more is stored in central vs. peripheral depots, resulting in a patterned change in body shape with parity.

Dietary patterns and associated lifestyles in preconception, pregnancy and postpartum

OBJECTIVE

To identify dietary patterns in women who are planning immediate pregnancy in preconception, weeks 6, 10, 26 and 38 of pregnancy, and 6 months postpartum, and to describe how particular lifestyles, the body mass index (BMI) and sociodemographic factors are associated to these patterns.

DESIGN

Longitudinal study throughout the reproductive cycle of food consumption carried out in a Spanish Mediterranean city.

SETTING

Faculty of Medicine and Health Sciences, Rovira i Virgili University.

SUBJECTS

In total, 80 healthy female volunteers who were planning immediate pregnancy.

INTERVENTIONS

A seven-consecutive-day dietary record was used to evaluate the dietary intake. Exploratory factor analysis was used to identify the main dietary patterns in each of the periods. Fitted multiple linear regression models were used to study the associations between the lifestyle and sociodemographic variables, and each dietary pattern.

RESULTS

The 'sweetened beverages and sugars' pattern was identified from preconception to 6 months postpartum and the 'vegetables and meat' pattern to the end of pregnancy. The 'sweetened beverages and sugars' pattern is positively associated with smoking and negatively associated with physical activity before conception and in the first trimester of pregnancy. The 'vegetables and meat' pattern is negatively associated with the BMI during the preconception period and positively associated with age in weeks 10 and 38 of pregnancy. It is shown that the patterns do not change significantly throughout the period studied.

CONCLUSIONS

We have identified two stable dietary patterns from preconception to postpartum. The 'sweetened beverages and sugars' pattern is associated with habits of risk for the health of the pregnant woman and her offspring.

SPONSORSHIP

'Comisión Interministerial de Ciencia y Tecnología' (CICYT: ALI89-0388) and 'Instituto de Salud Carlos III', RCMN (C03/08), Madrid, Spain'.

Consequences of inadequate food energy and negative energy balance in humans

Energy deficiency is probably best measured in adults by the body mass index (BMI). Acute energy deficiency (AED) is associated with body weight loss, along with changes in body composition, as well as a reduced BMR and physical activity. Chronic energy deficiency (CED) is an inadequacy in food to which individuals adapt, at some cost. Individuals with this have never 'lost' weight: they have simply grown less. They adapt to the decreased food energy by reductions in their total energy expenditure (TEE), linked mainly to a lower body size, and to their physical activity. It seems unlikely that enhanced metabolic efficiency contributes substantially to energy saving in CED. Supplementation of energy deficient individuals is accompanied by significant fat deposition; this may have deleterious consequences. Women in many developing countries achieve a successful outcome to pregnancy in spite of being chronically undernourished. Reductions in basal metabolism and behavioural changes in the form of diminished physical activity could meet most of the extra energy needed for pregnancy. Milk energy output is maintained within the expected range in undernourished lactating mothers. Energy deficiency in children is best measured by height-for-age for stunting, and weight-for-height for wasting. Deficits in behavioural and functional parameters in children exist with undernutrition, and can be reduced by early nutritional supplementation along with the appropriate environment.

Determination of Maternal Body Composition in Pregnancy and Its Relevance to Perinatal Outcomes

Three models and 10 specific methods for determining maternal body composition are discussed and their perinatal relevance reviewed. English language publications (1950 to January 2004) were searched electronically and by hand. Search terms included "body composition," "human," " pregnancy," "obesity," "adiposity," "regional," "2-, 3-, 4-component," "truncal," "peripheral," "central," "visceral" along with specific techniques and outcomes listed subsequently. Three models of body composition are described: 2-component being fat and fat-free mass; 3-component being fat, water, and protein; and 4-component being fat, water, protein, and osseous mineral. Ten techniques of body composition assessment are described: 1) anthropometric techniques including skinfold thicknesses and waist-hip ratio; 2) total body water (isotopically labeled); 3) hydrodensitometry (underwater weighing); 4) air-displacement plethysmography; 5) bio-impedance analysis (BIA); 6) total body potassium (TBK); 7) dual-energy x-ray absorptiometry (DEXA); 8) computed tomography (CT); 9) magnetic resonance imaging (MRI); and 10) ultrasound (USS). Most methods estimate total adiposity. Regional fat distribution-central (truncal) compared with peripheral (limb) or visceral compared with subcutaneous-is important because of regional variation in adipocyte metabolism. Skinfolds, DEXA, CT, MRI, or USS can distinguish central from peripheral fat. CT, MRI, or USS can further subdivide central fat into visceral and subcutaneous. Perinatal outcomes examined in relation to body composition include pregnancy duration, birth weight, congenital anomalies, gestational diabetes, gestational hypertension, and the fetal origins of adult disease. A few studies suggest that central compared with peripheral fat correlates better with birth weight, gestational carbohydrate intolerance, and hypertension. Means of accurately assessing maternal body composition remain cumbersome and impractical, but may more accurately predict perinatal outcomes than traditional assessments such as maternal weight.

Estrogen regulation of growth hormone action

GH plays a pivotal role in regulating body growth and development, which is modulated by sex steroids. A close interplay between estrogen and GH leads to attainment of gender-specific body composition during puberty. The physiological basis of the interaction is not well understood. Most previous studies have focused on the effects of estrogen on GH secretion. There is also strong evidence that estrogen modulates GH action independent of secretion. Oral but not transdermal administration of estrogen impairs the metabolic action of GH in the liver, causing a fall in IGF-I production and fat oxidation. This results in a loss of lean tissue and a gain of body fat in postmenopausal women and an impairment of GH effect in hypopituitary women on GH replacement. The negative metabolic sequelae are potentially important because of the widespread use of oral estrogen and estrogen-related compounds. Estrogen affects GH action at the level of receptor expression and signaling. More recently, estrogen has been shown to inhibit Janus kinase/signal transducer and activator of transcription signaling by GH via the induction of suppressor of cytokine signaling-2, a protein inhibitor for cytokine signaling. This represents a novel paradigm of steroid regulation of cytokine receptors and is likely to have significance for a diverse range of cytokine function.

Consumo, hábitos alimentarios y estado nutricional de la población de Reus en la etapa preconcepcional, el embarazo y el posparto

BACKGROUND AND OBJECTIVE

To describe the evolution of food, energy and nutritional consumption at preconception, weeks 6, 10, 26 and 38 of pregnancy, and 6 and 26 weeks after birth.

SUBJECTS AND METHOD

Longitudinal evaluation of the nutritional status in 80 healthy volunteers with the intention of immediate conception was performed. Food consumption was estimated using the 7 day register. Toxic habits and physical activity in each phase were also estimated. Education level, weight, height and parity were recorded at preconception.

RESULTS

Food and nutritional consumption varied slightly between preconception and pregnancy with the exception of increased consumption of milk, fruit and vegetables and reduced consumption of sugars, sugar-containing and alcoholic drinks. Energy intake did not vary significantly during pregnancy but increased 6 weeks after birth, coinciding with lactation. However recommended energy intakes were not met in any of the phases of the study. Six months after birth, women had lower food, energy and nutritional intakes than during the preconception period. The probability of inadequate intake of iron, calcium, vitamin B6 and folates was increased in the last weeks of pregnancy and this continued until up to 6 months after birth.

CONCLUSIONS

In this study, pregnant women did not increase energy and nutritional intake during pregnancy with respect to the preconception period. Energy intake was increased immediately after birth, coinciding with lactation. Throughout the study, however, the reported consumption was lower than recommended daily intakes.

Energy requirements during pregnancy based on total energy expenditure and energy deposition

BACKGROUND

Energy requirements during pregnancy remain controversial because of uncertainties regarding maternal fat deposition and reductions in physical activity.

OBJECTIVE

This study was designed to estimate the energy requirements of healthy underweight, normal-weight, and overweight pregnant women and to explore energetic adaptations to pregnancy.

DESIGN

The energy requirements of 63 women [17 with a low body mass index (BMI; in kg/m(2)), 34 with a normal BMI, and 12 with a high BMI] were estimated at 0, 9, 22, and 36 wk of pregnancy and at 27 wk postpartum. Basal metabolic rate (BMR) was measured by calorimetry, total energy expenditure (TEE) by doubly labeled water, and activity energy expenditure (AEE) as TEE - BMR. Energy deposition was calculated from changes in body protein and fat. Energy requirements equaled the sum of TEE and energy deposition.

RESULTS

BMR increased gradually throughout pregnancy at a mean (+/-SD) rate of 10.7 +/- 5.4 kcal/gestational week, whereas TEE increased by 5.2 +/- 12.8 kcal/gestational week, which indicated a slight decrease in AEE. Energy costs of pregnancy depended on BMI group. Although total protein deposition did not differ significantly by BMI group (mean for the 3 groups: 611 g protein), FM deposition did (5.3, 4.6, and 8.4 kg FM in the low-, normal-, and high-BMI groups; P = 0.02). Thus, energy costs differed significantly by BMI group (P = 0.02). In the normal-BMI group, energy requirements increased negligibly in the first trimester, by 350 kcal/d in the second trimester, and by 500 kcal/d in the third trimester.

CONCLUSION

Extra energy intake is required by healthy pregnant women to support adequate gestational weight gain and increases in BMR, which are not totally offset by reductions in AEE.

Energy stress during pregnancy and lactation: consequences for maternal nutrition in rural Bangladesh

OBJECTIVE

To assess the relationship of energy stress during pregnancy and lactation to maternal body stores in marginally nourished rural Bangladeshi women.

SUBJECTS AND METHODS

Two-hundred and fifty-two women were followed from 5-7 months of pregnancy until 6 months postpartum. Energy intake was estimated during pregnancy and at 1, 3 and 6 month(s) postpartum using 24 h dietary recall. Body weight was measured on enrollment, another once or twice during pregnancy, and at 1, 3 and 6 month(s) postpartum. The weekly rates of pregnancy weight gain and postpartum weight changes were determined. Weight and length of the infants were measured at birth and at approximately 1, 3 and 6 month(s).

RESULTS

Maternal energy intake at 5-7 months of gestation was 1464+/-416 kcal/day (mean+/-s.d.). Women gained a mean of 200 g/week or a total of 4 kg during the second half of pregnancy. An analysis of maternal weight showed no indication of accrual of fat stores during pregnancy. Dietary energy during lactation exceeded the intake during pregnancy by 248-354 kcal/day. Mothers lost an estimated average of 1 kg of weight during the first 6 months of lactation. The mean (+/-s.d.) birth weight was 2.55+/-0.38 kg, and the prevalence of low birth weight (<2500 g) was 48%. Infants exhibited some catch-up growth only during the first 3 months but overall growth during the first 6 months did not change from their relative status at birth when compared with NCHS reference.

CONCLUSIONS

These rural Bangladeshi women failed to gain sufficient weight during the last half of pregnancy to maintain body weight during lactation when the energy demand is high. Poor growth of their primarily breastfed infants raises concern about the adequacy of lactation in this community.

Comparative and evolutionary dimensions of the energetics of human pregnancy and lactation

The purpose of this article is to compare the energetics of reproduction for human and other primates in order to evaluate the extent to which human reproductive energetics are distinct from other primates and other large-bodied placental mammals. The article also evaluates the energetics of human and primate gestation and lactation using data from a variety of different populations living under different environmental circumstances. Energetics refers to energy intake and expenditure, and changes in body fat stores. Human and nonhuman primates have longer periods of gestation and lactation and slower prenatal and postnatal growth than other mammals of similar size. This reduces daily maternal energy costs. The development of sizable fat stores is not unique to humans, but fat stores are typically greater in human females and may play a greater role in reproduction. The strategies used to meet the energy costs of pregnancy vary among populations of humans and nonhuman primates and among humans interindividual variability is high. In pregnancy, some increase energy intake but others apparently do not. Increases in metabolic efficiency are evident in some human populations, whereas decreases in physical activity occur, but are not seen in all human or primate populations. Lactation is more energetically costly on a daily basis among humans and nonhuman primates, but has not been as well studied. It appears that both nonhuman and human primates tend to increase energy intake to meet in part the cost of lactation. They also use other strategies such as relying on body tissue stores, reductions in physical activity, and/or increases in metabolic efficiency to meet the remainder of the cost. It is also clear that human females in different populations and different women in the same population use a different combination of strategies to meet the cost of lactation.

Nitrogen balance of healthy Dutch women before and during pregnancy

BACKGROUND

Experimental studies including longitudinal nitrogen balance studies could provide insight into protein metabolism in pregnancy.

OBJECTIVE

Our aim was to determine the development of nitrogen balance during pregnancy compared with nitrogen balance before pregnancy in women consuming imposed constant diets. We also tracked changes in muscle mass and lean body mass by measuring urinary 3-methylhistidine (3-MeH) and urinary creatinine.

DESIGN

Nitrogen balance was determined over 8 d in 12 healthy Dutch women before pregnancy and at weeks 12, 23, and 34 of gestation. Complete daily diets were supplied during each balance period so that each subject's energy, protein, and macronutrient intakes were similar in amount and composition in all 4 balance periods.

RESULTS

Throughout pregnancy there was no significant change in loss of nitrogen in feces and therefore no change in protein digestibility. The amount of nitrogen excreted in urine in late pregnancy (11.0 +/- 1.4 g/d) was significantly (P < 0.01) less than in early pregnancy (12.6 +/- 1.3 g/d). Nitrogen retention increased toward term, even though energy balance became progressively negative. The difference between the first (-0.4 +/- 1.7 g N/d) and third (1.2 +/- 1.6 g N/d) trimester was significant (P < 0.05). No differences were found in either 3-MeH or creatinine excretion between trimesters.

CONCLUSIONS

These urinary nitrogen excretion and nitrogen retention data show that when the dietary supply remains constant, nitrogen balance increases toward the end of pregnancy, suggesting a more efficient use of dietary protein later in pregnancy. Urinary 3-MeH and creatinine excretion indicated no change in protein metabolism.

Thermal environment and human birth weight

Human birth weight is known to be influenced by several factors, including maternal energy supply, maternal stature, disease status, smoking status and gestation length. This article proposes that the thermal environment may be a further factor influencing birth weight. Experimental animal studies demonstrate clear effects of thermal stress on placental function and birth weight, but may have limited relevance for humans due to between-species differences in pregnancy physiology. Observational studies suggest an inverse relationship between environmental temperature and birth weight within and between human populations. Variation in maternal size, body fatness, pregnancy weight gain and heat production is predicted to influence maternal thermoregulatory capacity, as are the size and composition of the foetus. These associations generate the hypothesis that low birth weight in hot environments may in part represent an adaptation to environmental heat stress.

Energy adaptations in human pregnancy: limits and long-term consequences

The very slow rate of human fetal growth generates a lower incremental energy stress than in any other mammalian species. This creates a situation in which adaptive changes in metabolic rate and in the amount of additional maternal fat stored during gestation can make a profound difference to the overall energy needs of pregnancy. Comparisons of women in affluent and poor countries have recorded mean population energy needs ranging from as high as 520 MJ to as low as -30 MJ per pregnancy. These energy costs are closely correlated with maternal energy status when analyzed both between and within populations, suggesting that they represent functional adaptations that have been selected for their role in protecting fetal growth. Although this metabolic plasticity represents a powerful mechanism for sustaining pregnancy under very marginal nutritional conditions, it must not be construed as a perfect mechanism that obviates the need for optimal nutritional care of pregnant women. The fact that fetal weight represents up to 60% of total pregnancy weight gain in many pregnancies in poor societies (compared with a well-nourished norm of 25%) indicates that the fetus is developing under suboptimal nutritional and physiologic conditions. It has long been recognized that this has immediate consequences for the offspring in terms of increased perinatal mortality. The more recent appreciation that impaired fetal growth may also precipitate longer-term defects in terms of adult susceptibility to noncommunicable and infectious diseases reinforces the view that pregnancy may be the most sensitive period of the life cycle in which nutritional intervention may reap the greatest benefits.

Physiology of pregnancy and nutrient metabolism

Pregnancy consists of a series of small, continuous physiologic adjustments that affect the metabolism of all nutrients. The adjustments undoubtedly vary widely from woman to woman depending on her prepregnancy nutrition, genetic determinants of fetal size, and maternal lifestyle behavior. Studies of protein and energy metabolism illustrate the potential of adjusting the use of those nutrients to conserve a fetal supply. Adjustments in the metabolism of nitrogenous compounds are in place by the second quarter of pregnancy. During the last quarter of pregnancy, when fetal demands are greatest, those adjustments allow a positive nitrogen retention. The energy requirement of basal metabolism is influenced by maternal prepregnant nutrition and by fetal size. If maternal energy reserves are low at conception, the basal metabolic rate is down-regulated to conserve energy. Also, women having larger babies tend to have greater increases in their basal metabolic rate and lower rates of maternal energy storage. Changes in maternal food and physical activity behaviors during gestation may augment the physiologic adjustments. However, the substantial variability in food intakes and physical activity makes it difficult to show those changes. Thresholds in the capacity to adjust nutrient use to the amount supplied exist for all nutrients. When intakes fall below the threshold, fetal growth and development is affected more than is maternal health. Efforts to achieve good maternal nutritional status preconception as well as throughout gestation best assure a good milieu for fetal growth and development.

Longitudinal assessment of energy balance in well-nourished, pregnant women

BACKGROUND

Clinicians often recommend an additional energy intake of 1250 kJ/d to their pregnant patients. Previous studies have shown considerable variation in the metabolic response to pregnancy and thus in the additional energy required to support a pregnancy.

OBJECTIVE

The purpose of this study was to assess how well-nourished women meet the energy demands of pregnancy and to identify factors that predict an individual's metabolic response.

DESIGN

Resting metabolic rate (RMR), diet-induced thermogenesis (DIT), total energy expenditure (TEE), activity energy expenditure (AEE), energy intake (EI), and body fat mass (FM) were measured longitudinally in 10 women preconception; at 8-10, 24-26, and 34-36 wk of gestation; and 4-6 wk postpartum.

RESULTS

Compared with preconception values, individual RMRs increased from 456 to 3389 kJ/d by late pregnancy. DIT varied from -266 to 110 kJ/meal, TEE from -105 to 3421 kJ/d, AEE from -2301 to 2929 kJ/d, EI from -259 to 2176 kJ/d, and FM from a 0.6-kg loss to a 10.6-kg gain. The only prepregnant factor that predicted FM gain was RMR (r = 0.65, P < 0.05). Women with the largest cumulative increase in RMR deposited the least FM (r = -0.64, P < 0.05).

CONCLUSIONS

Well-nourished women use different strategies to meet the energy demands of pregnancy, including reductions in DIT or AEE, increases in EI, and deposition of less FM than anticipated. The combination of strategies used by individual women is not wholly predictable from prepregnant indexes. The use of a single recommendation for increased energy intake in all pregnant women is not justified.

Longitudinal changes in body composition and energy balance in lean women with normal and abnormal glucose tolerance during pregnancy

OBJECTIVE

The objective of this study was to evaluate the longitudinal changes in energy expenditure and body composition in relationship to alterations in carbohydrate metabolism in women with normal and abnormal glucose metabolism. We hypothesized that women with decreased insulin sensitivity before conception would have less fat accretion and smaller increases in energy expenditure.

STUDY DESIGN

Six women with normal glucose tolerance and 10 women with abnormal glucose tolerance were evaluated before conception, and in early (12 to 14 weeks) and late (34 to 36 weeks) gestation. Body composition was estimated by hydrodensitometry, resting energy expenditure, and glucose and fat metabolism by indirect calorimetry, endogenous glucose production by infusion of [6-6 2H2] glucose, and insulin sensitivity using a hyperinsulinemic-euglycemic clamp (40 mU/m2/min).

RESULTS

There was a smaller increase in fat mass (1.3 kg [P = .04]) in early pregnancy in women with abnormal glucose tolerance before pregnancy. Indirect calorimetry measured gestational age-related increases in basal oxygen utilization, with or without correction for fat-free mass (VO2, P = .002), resting energy expenditure (expressed in kilocalories, P = .0001), and carbohydrate oxidation (P = .0003). The insulin-mediated elevation in VO2 increased in later gestation VO2 (P = .005), as did resting energy expenditure (P = .0001) and fat oxidation (P = 0.0001). However, there was a decrease in respiratory quotient (P = .0001), carbohydrate oxidation (P = .002), and nonoxidative carbohydrate metabolism (P = .0001) with advancing gestation during insulin infusion. In early pregnancy, changes in fat mass correlated inversely with changes in insulin sensitivity (r= -0.52, P = .04) and changes in basal VO2 correlated inversely with decreases in basal endogenous glucose production (r = -0.74, P = .01).

CONCLUSION

In early gestation, the changes in maternal fat mass and basal oxygen consumption are inversely related to the changes in insulin sensitivity. This response in lean women with decreased insulin sensitivity before conception may have survival value by providing a larger amount of available substrate to meet fetoplacental needs during gestation.

Maternal nutrition and obstetric outcome

In general, maternal nutritional status in civilized countries is not at risk. However, even a marginal malnutritional state for some (micro)nutrients for the pregnant women can adversely affect obstetrical outcome. From the data available so far, only folic acid supplementation is advised. However, the importance of an adequate iron and zinc status has to be stressed. In addition, women should be warned preconceptionally about excessive intake of vitamins, especially of those products containing large amounts of vitamin A.

Estimating body composition in late gestation: a new hydration constant for body density and total body water

Twenty women underwent body density (DB) measurements using underwater weighing with correction of residual lung volume by nitrogen dilution and total body water (TBW) using isotope dilution of 18O to estimate body composition at 30 wk of gestation. DB and TBW were used as independent variables in the same equation. The hydration constant (HC) of fat-free mass (FFM) was estimated as 0.762; based on this HC, new body composition equations for both DB and TBW were derived. These equations were prospectively tested in an additional 20 women at 30 wk of gestation. No significant differences were detected between estimates of percent body fat (%F) using either the newly derived DB or TBW equations and estimates of %F using both DB and TBW. Ten of these forty women were evaluated postpartum. There was no significant difference in %F estimated by either TBW or DB compared with standard equations (hydration of FFM = 0.72) and %F using both DB and TBW. These results highlight the importance of either measuring both DB and TBW or using an appropriate hydration constant for FFM in estimating body composition during pregnancy or conditions associated with increased body water.

Thyroid function and thyroid size in normal pregnant women living in an iodine replete area

OBJECTIVE

The interpretation of the changes in thyroid hormone concentrations during normal pregnancy is a matter of debate involving, in some geographical regions, enhanced thyroid activity in early pregnancy and a hypothyroid state in the third trimester. A clinically detectable increase in thyroid size has been found in areas of mild iodine deficiency ('goitre of pregnancy'), but not in iodine replete areas.

DESIGN

A prospective study. We have studied thyroid size and function in normal pregnant women living in an iodine replete area.

PATIENTS

Healthy women before and during a normal pregnancy resulting from artificial insemination (n = 10) and other women during the normal menstrual cycle (n = 11), in the iodine replete area of Amsterdam.

MEASUREMENTS

Thyroid volume was measured by ultrasonography. Plasma T4, free T3, free reverse T3, TSH, thyroxine binding globulin, hCG, progesterone and thyroid autoantibodies were measured.

RESULTS

Thyroid volume did not change during pregnancy (data given before pregnancy and during 1st, 2nd and 3rd trimesters, respectively: 10.3 +/- 5.1, 10.6 +/- 4.4, 9.6 +/- 3.8 and 9.4 +/- 3.0 ml, NS). Free T4 and free T3 levels declined during pregnancy (13.7 +/- 2.0, 13.5 +/- 4.1, 11.2 +/- 2.8, 10.2 +/- 1.6 pmol/l, P = 0.005; 4.55 +/- 0.63, 4.64 +/- 0.88, 3.72 +/- 0.67 and 4.01 +/- 0.75 pmol/l, P = 0.003), whereas free reverse T3 levels increased during pregnancy (0.16 +/- 0.04, 0.19 +/- 0.07, 0.14 +/- 0.03 and 0.20 +/- 0.07 pmol/l, P = 0.001). Thyroglobulin levels remained unchanged. Thyroid hormones and thyroid volume did not differ between follicular and luteal phases of the menstrual cycle.

CONCLUSION

Thyroid volume does not increase during pregnancy in iodine-replete areas. The decrease in free T4 and free T3 and the increase in free reverse T3 concentrations during pregnancy resemble the changes in thyroid hormones seen in non-thyroidal illness. This could be a physiological adaptation enabling energy conservation during the high metabolic demands of pregnancy.

Energy-sparing strategies to protect human fetal growth

OBJECTIVES

Our purpose was to test whether energy-sensitive adjustments in gestational metabolism, previously observed in studies of Gambian and British women, are a general phenomenon and to define the nutritional factors that direct them.

STUDY DESIGN

Retrospective analysis of data on basal metabolic rate and fat deposition in 360 pregnancies from 10 studies in a wide range of nutritional settings was performed.

RESULTS

The energy costs of pregnancy varied widely between different communities: maintenance costs from -45 to +210 MJ, fat deposition from -23 to +267 MJ, and total energy costs from -20 to +523 MJ. Total costs were correlated with prepregnancy fatness (r = 0.80, p < 0.01) and pregnancy weight gain (r = 0.94, p < 0.001). Marginally nourished women conserved energy by suppressing metabolic rate and by gaining little fat.

CONCLUSIONS

The energy needs of pregnancy are modulated over a wide range in response to maternal energy status. This may be an important means of protecting fetal growth.

No substantial reduction of the thermic effect of a meal during pregnancy in well-nourished Dutch women

To investigate changes in the thermic effect of a meal (TEM) during pregnancy, metabolic rate was measured in the fasting state and during the first 180 min after consumption of a standardized test meal in twenty-seven women before, and in each trimester of pregnancy. Resting metabolic rate (RMR) showed a steady increase over pregnancy: values in weeks 24 and 35 of pregnancy were significantly higher than the prepregnancy baseline (Tukey's studentized range test). The pattern of changes of postprandial metabolic rate (PPMR) was similar to that of RMR. Consequently TEM, calculated as PPMR minus RMR, did not change over pregnancy; mean TEM values (kJ/180 min) before and in weeks 13, 24 and 35 of pregnancy were 117.3 (SD 19.4), 116.4 (SD 23.7), 111.6 (SD 24.4) and 111.5 (SD 26.7) respectively. We consider changes in TEM of less than 15% to be of little importance physiologically. If true changes in TEM over pregnancy are 15% or more we would have had a 90% chance of observing significant changes in TEM in the present study, given the number of subjects and the methods used. Therefore, we conclude that no substantial reduction in TEM occurs during pregnancy.