Maternal fat stores and fat accretion during pregnancy in relation to infant birthweight

A Dynamical Systems Model of Intrauterine Fetal Growth

The underlying mechanisms for how maternal perinatal obesity and intrauterine environment influence fetal development are not well understood and thus require further understanding. In this paper, energy balance concepts are used to develop a comprehensive dynamical systems model for fetal growth that illustrates how maternal factors (energy intake and physical activity) influence fetal weight and related components (fat mass, fat-free mass, and placental volume) over time. The model is estimated from intensive measurements of fetal weight and placental volume obtained as part of Healthy Mom Zone (HMZ), a novel intervention for managing gestational weight gain in obese/overweight women. The overall result of the modeling procedure is a parsimonious system of equations that reliably predicts fetal weight gain and birth weight based on a sensible number of assessments. This model can inform clinical care recommendations as well as how adaptive interventions, such as HMZ, can influence fetal growth and birth outcomes.

The New "Obstetrical Dilemma": Stunting, Obesity and the Risk of Obstructed Labour

The "obstetrical dilemma" refers to the tight fit between maternal pelvic dimensions and neonatal size at delivery. Most interest traditionally focused on its generic significance for humans, for example our neonatal altriciality and our complex and lengthy birth process. Across contemporary populations, however, the obstetrical dilemma manifests substantial variability, illustrated by differences in the incidence of cephalo-pelvic disproportion, obstructed labour and cesarean section. Beyond accounting for 12% of maternal mortality worldwide, obstructed labour also imposes a huge burden of maternal morbidity, in particular through debilitating birth injuries. This article explores how the double burden of malnutrition and the global obesity epidemic may be reshaping the obstetrical dilemma. First, short maternal stature increases the risk of obstructed labour, while early age at marriage also risks pregnancy before pelvic growth is completed. Second, maternal obesity increases the risk of macrosomic offspring. In some populations, short maternal stature may also promote the risk of gestational diabetes, another risk factor for macrosomic offspring. These nutritional influences are furthermore sensitive to social values relating to issues such as maternal and child nutrition, gender inequality and age at marriage. Secular trends in maternal obesity are substantially greater than those in adult stature, especially in low- and middle-income countries. The association between the dual burden of malnutrition and the obstetrical dilemma is therefore expected to increase, because the obesity epidemic is emerging faster than stunting is being resolved. However, we currently lack objective population-specific data on the association between maternal obesity and birth injuries. Anat Rec, 300:716-731, 2017. © 2017 Wiley Periodicals, Inc.

The impact of maternal adiposity specialization on infant birthweight: upper versus lower body fat

BACKGROUND

The specialization of human fat deposits is an inquiry of special importance in the study of fetal growth. It has been theorized that maternal lower-body fat is designated specifically for lactation and not for the growth of the fetus.

OBJECTIVE

Our goal was to compare the contributions of maternal upper-body versus lower-body adiposity to infant birth weight. We hypothesized that upper-body adiposity would be strongly associated with infant birth weight and that lower-body adiposity would be weakly or negligibly associated with infant birth weight-after adjusting for known determinants.

STUDY DESIGN

In this prospective cohort study, 355 women initiated medical pre-natal care during the first trimester of pregnancy at The University of Oklahoma Health Sciences Center during 1990-1993. Maternal anthropometric measurements were assessed at the first clinic visit: (a) height; (b) weight; (c) circumferences of the upper arm, forearm, and thigh; and, (d) skin-fold measurements of the bicep, subscapular region, and thigh.

RESULTS

Infant birth weight was regressed on known major determinants to create the foundational model. Maternal anthropometric variables subsequently were added one at a time into this multiple regression model. The highest contribution by a single anthropometric variable to infant birthweight was, in order: subscapular skin-fold, forearm circumference, and thigh circumference. With one upper-body (subscapular skin-fold) and one lower-body (circumference of the thigh) adiposity measure in the model, the z-score regression coefficient (s.e.) was 85.7g (30.8) [p=0.0057] for maternal subscapular skin-fold and 19.0g (31.6) [p=0.5477] for circumference of the thigh. When the second-best upper-body contributor to infant birthweight (circumference of the forearm) was entered with one lower-body measure into the model, the z-score regression coefficient (s.e.) was 77.5g (38.5) [p=0.0451] for maternal forearm circumference and 14.1g (38.5) [p=0.7146] for circumference of the thigh. When both subscapular skinfold and forearm circumference were added to the model in place of BMI, the explained variance (r²=0.5478) was similar to the model using BMI (r²=0.5487).

CONCLUSION

Upper-body adiposity - whether operationalized by subscapular skin-fold or circumference of the forearm - was a markedly larger determinant of infant birth weight than lower-body adiposity.

Effects of an antenatal dietary intervention on maternal anthropometric measures in pregnant women with obesity

OBJECTIVE

The effect of providing antenatal dietary and lifestyle advice on secondary measures of maternal anthropometry was evaluated and their correlation with both gestational weight gain and infant birth weight was assessed.

METHODS

In a multicenter, randomized controlled trial, pregnant women with BMI of ≥25 kg/m(2) received either Lifestyle Advice or Standard Care. Maternal anthropometric outcomes included arm circumference, biceps, triceps, and subscapular skinfold thickness measurements (SFTM), percentage body fat (BF), gestational weight gain, and infant birth weight. The intention to treat principles were utilized by the analyses.

RESULTS

The measurements were obtained from 807 (74.7%) women in the Lifestyle Advice Group and 775 (72.3%) women in the Standard Care Group. There were no statistically significant differences identified between the treatment groups with regards to arm circumference, biceps, triceps, and subscapular SFTM, or percentage BF at 36-week gestation. Maternal anthropometric measurements were not significantly correlated with either gestational weight gain or infant birth weight.

CONCLUSIONS

Among pregnant women with a BMI of ≥25 kg/m(2) , maternal SFTM were not modified by an antenatal dietary and lifestyle intervention. Furthermore, maternal SFTM correlate poorly with both gestational weight gain and infant birth weight.

Maternal behaviors during pregnancy impact offspring obesity risk

This study investigated the effects of maternal changes during pregnancy in diet, exercise, and psychosocial factors on offspring weight parameters at birth and 6 months. In overweight/obese (OW/OB; n = 132) mothers, greater % kcal from sweets early in pregnancy was the strongest, independent predictor of higher weight for age (WFA) (beta = 0.19; P = 0.004), higher odds of macrosomia (OR = 1.1 (1.0-1.2); P = 0.004) and WFA >90th percentile at birth (OR = 1.2 (1.1-1.3); P = 0.002) and higher WFA at 6 months (beta = 0.30; P = 0.002). In normal weight (n = 153) mothers, higher intake of soft drinks was the strongest predictor of higher offspring WFA at birth (beta = 0.16; P = 0.04) but not at 6 months. Prenatal physical activity, depressive symptoms, and sleep-related variables did not significantly predict offspring weight outcomes. Mothers' eating behaviors during pregnancy, especially intake of sweets in OW/OB mothers, may have a lasting effect on child weight.

Maternal body composition, HIV infection and other predictors of gestation length and birth size in Zimbabwe

The role of maternal infections, nutritional status and obstetric history in low birth weight is not clear. Thus, the objective of the present study was to assess the effects of maternal HIV infection, nutritional status and obstetric history, and season of birth on gestation length and birth size. The study population was 1669 antenatal care attendees in Harare, Zimbabwe. A prospective cohort study was conducted as part of a randomised, controlled trial. Maternal anthropometry, age, gravidity, and HIV status and load were assessed in 22nd–35th weeks gestation. Outcomes were gestation length and birth size. Birth data were available from 1106 (66·3%) women, of which 360 (32·5%) had HIV infection. Mean gestation length was 39·1 weeks with 16·6% <37 weeks, mean birth weight was 3030 g with 10·5% <2500 g. Gestation length increased with age in primigravidae, but not multigravidae (interaction, P=0·005), and birth in the early dry season, low arm fat area, multiple pregnancies and maternal HIV load were negative predictors. Birth weight increased with maternal height, and birth in the late rainy and early dry season; primi-secundigravidity, low arm fat area, HIV load, multiple pregnancies and female sex were negative predictors. In conclusion, gestation length and birth weight decline with increasing maternal HIV load. In addition, season of birth, gravidity, maternal height and body fat mass, and infant sex are predictors of birth weight.

Maternal lean body mass may be the major determinant of birth weight: a study from India

This study explored the relationship of maternal body composition parameters to the birth weight of the offspring. Maternal anthropometric parameters (weight, height) and body composition by dual energy X-ray absorptiometry were measured in 76 women from low-income group during 12-21 days postpartum. The mean+/-s.d. height, weight of the mothers and birth weight of the newborns were 151.5+/-5.29 cm, 46.7+/-6.04 and 2.84+/-0.358 kg, respectively. When the relationship of maternal anthropometric and body composition parameters to the infants' birth weight was studied, maternal lean body mass was found to be the most important determinant of birth weight (R2 (%) = 21.3) (P < 0.001). This study highlights the importance of increasing lean body mass in young women for better pregnancy outcome.

Relationship between dietary intake of cod liver oil in early pregnancy and birthweight

OBJECTIVE

To investigate the possible association between birth outcome and marine food and cod liver oil intake of healthy women in early (prior to 15 weeks of gestation) pregnancy.

DESIGN

An observational study.

SETTING

Free-living conditions in a community with traditional fish and cod liver oil consumption.

POPULATION

Four hundred and thirty-five healthy pregnant Icelandic women without antenatal and intrapartum complications.

METHODS

Dietary intake of the women was estimated with a semi-quantitative food frequency questionnaire (FFQ) covering food intake together with lifestyle factors for the previous three months. Questionnaires were filled out at between 11 and 15 weeks and between 34 and 37 weeks of gestation. The estimated intake of marine food and cod liver oil was compared with birthweight by linear and logistic regression controlling for potential confounding.

MAIN OUTCOME MEASURES

Birthweight, cod liver oil intake, lifestyle factors (alcohol, smoking).

RESULTS

Fourteen percent of the study population used liquid cod liver oil in early pregnancy. Regression analysis shows that these women gave birth to heavier babies (P < 0.001), even after adjusting for the length of gestation and other confounding.

CONCLUSIONS

Maternal intake of liquid cod liver oil early in pregnancy was associated with a higher birthweight. Higher birthweight has been associated with a lower risk of diseases later in life and maternal cod liver oil intake might be one of the means for achieving higher birthweight.

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.

Bioelectrical impedance analysis during pregnancy and neonatal birth weight

OBJECTIVE

To generate reference ranges for bioelectrical impedance indices throughout pregnancy and to investigate whether a relationship exists between these indices and the neonatal birth weight.

STUDY DESIGN

Pregnant women with a singleton gestation, gestational age lower than 12 weeks, and absence of medical diseases before pregnancy were enrolled. Patients with pregnancy complications, such as hypertensive disorders, diabetes, and antiphospholipides syndrome were excluded. Antrophometric maternal parameters and bioelectrical impedance measurements were performed during the first, second, third trimester of pregnancy, at delivery and 60 days after delivery. Height(2)/resistance (cm(2)/Omega) and height(2)/reactance (cm(2)/Omega) were utilized to estimate the total and extracellular body water amounts, respectively. Spearman rank correlations and cox proportional hazard modelling were used for statistical purposes.

RESULTS

169 patients completed all measurements. Total and extracellular water amounts significantly increase as pregnancy advances and return to the pre-pregnancy values within 60 days after delivery. After adjustment for gestational age at delivery, fetal sex, and smoking habits, height(2)/resistance at 25 weeks (hazard=1.04, 95% confidence interval (CI) 1.02-1.06, P<0.005), height(2)/resistance at 30 weeks (hazard=1.03, 95% CI 1.01-1.05, P<0.005), height(2)/reactance at 20 weeks (hazard=1.03,95% CI 1.01-1.05, P<0.005), and height(2)/reactance at 25 weeks (hazard=1.03, 95% CI 1.01-1.04, P<0.01) were found to be independent predictors of birth weight.

CONCLUSION

We have provided reference ranges for bioimpedance analysis during pregnancy, an easy, fast and non invasive method to estimate the body water composition during pregnancy. Bioelectrical impedance indices during the second trimester of pregnancy are independently related to the birth weight.

Unexpected relationship between fat mass and basal metabolic rate in pregnant women

We investigated the relationships between BMR, fat-free mass (FFM) and fat mass in pregnancy. BMR was measured by indirect calorimetry and body composition was assessed by densitometry in seventeen non-pregnant women (79.9 (SD 26.3, range 50.5-151.4) kg) and sixteen pregnant women (75.7 (SD 20.6, range 54.5-115.9) kg). The pregnant women were evaluated during weeks 31-35 of gestation. Multiple regression analysis of BMR with FFM and fat mass in the non-pregnant women showed that FFM was a highly significant predictor of BMR (P < 0.0001), but fat mass was not (P = 0.09). In contrast, in the pregnant women, multiple regression analysis revealed that fat mass was a highly significant predictor (P < 0.001), while FFM was not (P = 0.69). Evaluation of the interaction terms in the combined data set confirmed that the relationships of BMR with FFM and fat mass differ significantly in non-pregnant and pregnant women. It is proposed that pregnancy represents a unique condition during which BMR is regulated by maternal adipose reserves. An augmented BMR in overweight pregnant women may be protective, given that excessive weight gain may be detrimental to neonatal and maternal health.

Body composition and fat distribution during the first 2 weeks of gestation in ad lib.-fed and energy-restricted rats

Knowledge about changes in body composition during gestation is of interest when estimating energy requirements during pregnancy, and relevant since reproduction is often surprisingly well maintained in malnourished females. Due to difficulties in conducting such studies in humans, studies in rats are of interest. Therefore, maternal retention of fat and fat-free weight was estimated in rats during the first 2 weeks of gestation and during a corresponding time period in virgin controls. Groups fed ad lib. or 70% of ad lib. intake during the 4 weeks preceding conception and during gestation were studied. Retention was estimated by comparing pregnant and virgin rats with rats killed at the time of conception. Body fat was analysed chemically and fat-free weight was body weight minus body fat. Each rat was divided into twelve to fourteen parts and the fat content of each part was analysed. Pregnant ad lib.-fed rats retained more fat and fat-free weight than did virgin ad lib.-fed controls. In the energy-restricted group the pregnant rats retained more fat-free weight while virgin rats retained slightly more fat than did pregnant rats. The difference between pregnant and virgin rats with respect to the amount of fat in the different body parts was small in both feeding groups. Thus, the statement that fat stored at specific sites in the maternal body represents an important source of energy for use during lactation was not supported. The findings suggest that pregnancy stimulates growth of the maternal body and that chronic moderate energy restriction curtails this growth.

Effect of fat and fat-free mass deposition during pregnancy on birth weight

OBJECTIVES

The purposes of our study were to describe the patterns and location of fat and fat-free mass deposition during pregnancy and to evaluate their effects on fetal growth.

STUDY DESIGN

Our study is a prospective follow-up of 105 healthy pregnant women who were delivered of term infants. Body composition was evaluated eight times during gestation with anthropometric measures and bioimpedance techniques. Body fat and fat-free mass were calculated with equations specifically developed for this population.

RESULTS

Total weight gain was 10.0 +/- 3.5 kg; net weight gain was 3.7 +/- 0.31 kg; birth weight was 3211 +/- 467 gm (values are mean +/- SEM). In these women fat was deposited mostly in the thigh and subscapular region for a total of 6.23 +/- 0.19 kg at term. The period of pregnancy of the largest maternal fat deposition per week is between the twentieth and thirtieth weeks. After adjusting by prepregnancy weight, birth weight is associated with maternal changes in thigh skin folds and fat gain before the thirtieth week of gestation. Infants born to mothers with low fat gain before the thirtieth week were 204 gm lighter than infants born to mothers with fat gain > or = 25th percentile of this population.

CONCLUSION

Maternal nutritional status at the beginning of gestation and the rate of fat gain early in pregnancy are the two nutritional indicators most strongly associated with fetal growth in this population.

Women who gain more fat during pregnancy may not have bigger babies: implications for recommended weight gain during pregnancy

The correlation between infant birthweight and the amount of fat gained during pregnancy (estimated as the change in maternal weight between 10 weeks gestation and 2-3 weeks postpartum) was studied in 115 healthy, parous, urban Scottish housewives. There was very little correlation between these variables (r = 0.13, falling to r = 0.07 after birthweight was adjusted for initial maternal weight and length of gestation), i.e., women who gained more fat during their pregnancies did not give birth to heavier babies. This suggests that for most women one of the principal effects of increasing food intake during pregnancy may be to increase maternal fat gain rather than promote fetal growth, and that efforts to increase birthweight by encouraging greater weight gain during pregnancy may be unsuccessful.

Gestational diabetes-perinatal outcome with a policy of liberal and intensive insulin therapy

During 3 years of continuous screening for gestational diabetes mellitus in the county of Uppsala, 133 pregnant women (1.2%) were given this diagnosis. Maternal characteristics and the perinatal outcome of the pregnancies were examined retrospectively. Maternal overweight [body mass index greater than 23.9 kg/(m)2] was noted in 54.9% of the 133 women. Insulin therapy, with a mean daily dose of 42 U, was given to 62.4% of the patients, whereas the others were given dietary instructions alone. The frequency of infants with a birth weight greater than 2 SD was 24.1% and was significantly (p less than 0.025) related to pre-pregnancy overweight and also to pregnancy weight gain 18kg (p less than 0.01). Caesarean section was performed in 27% of the pregnancies complicated by diabetes, compared with the overall figure of 11% in Uppsala during the study period. Neonatal hypoglycaemia (blood glucose greater than or equal to 1.6 mM) was noted in 17.3% of the infants and was significantly (p less than 0.01) related to maternal sympathomimetic therapy. Despite liberal and intensive insulin therapy, there was a considerable rate of perinatal complications. Although not severe, they indicate a need for further improvement in the care of women with gestational diabetes.

Maternal somatostatin levels and their correlation with infant birth weight

Samples of blood were obtained from 52 primiparous breast-feeding women 4 days post partum. Thirty-six of the mothers were still breast-feeding 3-4 months later and had further blood samples taken. Somatostatin levels were analyzed by radioimmunoassay. A highly significant rank correlation (P = 0.0001) between average somatostatin levels on the two occasions was established, although somatostatin levels recorded 3-4 months post partum were significantly higher than those found 4 days post partum (P less than 0.01). Furthermore, somatostatin levels obtained 4 days and 3-4 months post partum were inversely related to the birth weight of their children (P = 0.006 and P = 0.03). The significant negative correlation between somatostatin levels recorded 4 days post partum and birth weight of the infants persisted only when non-smokers were investigated. A strong positive correlation between infant birth weight and weight of placenta was found (P = 0.0001) and a negative correlation (P = 0.04) between somatostatin levels and placental weight. A stepwise regression was performed to explain the importance of somatostatin levels in birth weight. Somatostatin levels and smoking had an almost equal influence on the variation in birth weight (approximately 10%). It is suggested that low maternal somatostatin levels are related to an efficient storage of nutrients in the fetoplacental unit, thereby leading to a high birth weight.

Placental hormones and maternal glucose metabolism. A study of fetal growth in normal pregnancy

The interrelations between three placental hormones (oestradiol, progesterone and hPL), maternal glucose metabolism, maternal anthropometry and fetal growth were studied in a sample of 52 carefully selected pregnant women. A relation was found between infant birthweight and both fasting blood glucose and t1/2 of glucose of an intravenous glucose tolerance test at week 37 of pregnancy. The serum concentrations of the placental hormones were not significantly related to the glucose variables. The correlation between birthweight and the maternal levels of hPL in late pregnancy (r = 0.60) persisted when fasting blood glucose and t1/2 of glucose were taken into account. Maternal fat mass was found to explain more of the variation in basal insulin levels around week 37 than did the placental hormones.

Maternal weight, weight gain and birthweight at term in the rural Tanzanian village of Ilula

In an area-based study in a rural Tanzanian village, the relations of maternal weight and weight gain during pregnancy to birthweight were analysed for 331 term deliveries. The distribution of body-mass index, used as an indicator of maternal nutritional status, was similar to the pattern seen in Sweden, although mean maternal height (156 cm) was 9 cm below that of Swedish women. Mean initial weight measured at week 14 was 53 kg and total pregnancy weight gain was 6 kg. Women weighing greater than or equal to 60 kg in early pregnancy gained less weight (0.16 kg/week) than those weighing less than 50 kg (0.22 kg/week). Birthweight was correlated both with maternal weight in early pregnancy and with weight gain during pregnancy, but only 10% of the variation in birthweight was explained by these maternal factors. Mean maternal weight 24 h postpartum was equal to the weight at 14 weeks of pregnancy, implying, on the average, no net weight gain. Women with a positive net weight gain had heavier babies than women with a negative net weight gain. Maternal anthropometric characteristics are important underlying determinants of intrauterine growth and birthweight, but they explain only a minor part of the variation and are of little value for screening purposes in individual women.

Energy intake and physical activity during pregnancy in relation to maternal fat accretion and infant birthweight

During the second pregnancy of 56 Swedish women resulting in a term birth, energy intake and physical activity were measured for 3 days at weeks 17 and 33. The values were related to maternal lean body mass, pregnancy weight gain, maternal fat accretion and infant birthweight by multiple linear regression analyses. A significant regression coefficient was found for energy intake at week 17 on maternal fat accretion. Energy intake was not significantly correlated with infant birthweight, not even when physical activity and maternal lean body mass were taken into account. Thus in a well-nourished Swedish population, energy intake is positively related to maternal fat accretion but not to the birthweight of term infants.