Changes in maternal abdominal subcutaneous fat layers using ultrasound: A longitudinal study

The Impact of Overweight and Obesity on Pregnancy: A Narrative Review of Physiological Consequences, Risks and Challenges in Prenatal Care, and Early Intervention Strategies

BACKGROUND

While substantial literature exists on the intersection of overweight/obesity (OWO) and pregnancy, much of it focuses on specific aspects, making it difficult to maintain an overview of clinically relevant factors for optimal care of OWO women throughout pregnancy.

OBJECTIVES

To provide a comprehensive synthesis of the existing literature, covering the full spectrum of clinically relevant information needed to manage OWO women from preconception to birth.

METHODS

For this narrative review a literature search was conducted on PubMed in January 2025. Eligible studies included full-text English articles with data from human subjects, with no restrictions on publication date.

FINDINGS

The impact of OWO on pregnancy is multifaceted, encompassing four interrelated themes: physiological consequences, emerging risks, challenges in prenatal care, and intervention strategies. OWO women exhibit differences in metabolic and inflammatory pathways compared to normal-weight women, reflected in altered laboratory tests. When managing gestational diabetes and preeclampsia, obesity-related characteristics must be considered. Clinicians need to be alert of obesity-mediated fetal complications, including overgrowth, malformations, stillbirth, and preterm birth, while navigating challenges in ultrasound measurements. Interventions during the preconception and prenatal periods provide key opportunities to optimize maternal weight and reduce the risk of long-term disease development.

CONCLUSION

The review's insights enhance clinical practice and call on researchers and policymakers to prioritize strategies that offer early counseling for obese pregnant women. These initiatives aim to optimize outcomes for both mother and child and contribute to combating the global obesity crisis.

Influence of the different hormonal status changes during their life on fat mass localisation in women: a narrative review

CONTEXT

Independently of the total body fat mass, upper body fat mass deposition is strongly associated with cardiometabolic comorbidities. The mechanisms underlying fat mass localisation are not fully understood, but evidences indicate sex-specific fat mass distribution. Currently, data on women are scarce and the link between hormonal status changes during their life and fat mass distribution is overlooked.

METHOD

For this narrative review, literature data were extracted from the PubMed and CENTRAL databases to examine the relationship between hormonal status and adipose tissue localisation in women.

RESULTS

Menopause strongly influences fat mass localisation, while the effect of the menstrual cycle phases, oral contraception use and pregnancy has not been unambiguously determined.

CONCLUSION

Reliable data are lacking on the relationship between hormonal variations throughout the lifespan and body fat mass localisation in women. Future studies should take into account the hormonal status of women to reduce the risk of cardiometabolic diseases.

Machine Learning-Based Prediction of Abdominal Subcutaneous Fat Thickness During Pregnancy

Objective: Current evidence regarding the safety of abdominal subcutaneous injections in pregnant women is limited. In this study, we developed a predictive model for abdominal skin-subcutaneous fat thickness (S-ScFT) by gestational periods (GP) in pregnant women. Methods: A total of 354 cases were measured for S-ScFT. Three machine learning algorithms, namely deep learning, random forest, and support vector machine, were used for S-ScFT predictive modeling and factor analysis for each abdominal site. Data analysis was performed using SPSS and RapidMiner softwares. Results: The deep learning algorithm best predicted the abdominal S-ScFT. The common important variables in all three algorithms for the prediction of abdominal S-ScFT were menarcheal age, prepregnancy weight, prepregnancy body mass index (categorized), large fetus for gestational age, and alcohol consumption. Conclusion: Predicting the safety of subcutaneous injections during pregnancy could be beneficial for managing gestational diabetes mellitus in pregnant women.

Abdominal skin subcutaneous fat thickness over the gestational period in Korean pregnant women: a descriptive observational study

Purpose

Although insulin is usually injected into the abdominal subcutaneous fat, in pregnancy women tend to avoid abdominal injections due to concern about fetal damage. Prior studies have been limited to only measuring skin-subcutaneous fat thickness (S-ScFT) at one site at specific pregnancy points. This study aimed to measure S-ScFT across several abdominal sites and over the gestational period in Korean pregnant women. This can identify which site would be relatively safe for subcutaneous injection during pregnancy.

Methods

Healthy women over 24 weeks of pregnancy in Korea were invited to voluntarily participate in this descriptive study. For the 142 women, S-ScFT of 12 sites in the abdomen were measured by ultrasound, several times over the pregnancy. Each incidence was treated as a case and a total of 262 cases were analyzed.

Results

The mean S-ScFT during pregnancy was 1.14±0.47 cm (1.25±0.54 cm at 24⁺⁰–27⁺⁶ weeks; 1.17±0.48 cm at 28⁺⁰–31⁺⁶ weeks; 1.09⁺⁰.40 cm at 32⁺⁰–35⁺⁶ weeks; and 1.06±0.47 cm at 36⁺⁰–40 weeks of pregnancy). Most S-ScFT were thicker than 10 mm. But S-ScFTs in the lateral abdomen and some sites were suboptimal (<6 mm), especially in the pre-pregnancy underweight body mass index group, who had a high rate of suboptimal thickness (27.1% overall and 33.9% in the lateral side).

Conclusion

The whole abdomen seems to be appropriate for subcutaneous injection in most Korean women during pregnancy, with a 4 to 5-mm short needle. However, for the lateral abdomen, making the skin fold might be needed for fetal safety.

The association of general obesity, central obesity and visceral body fat with the risk of gestational diabetes mellitus: Evidence from a systematic review and meta-analysis

BACKGROUND

Studies consistently reported that general obesity predicts gestational diabetes mellitus (GDM). However, whether other phenotypes of obesity such as central obesity and visceral adiposity might have differential associations as risk factors of GDM are less known. The objective of this study was to investigate the association of all these obesity phenotypes in developing GDM.

METHODS

PubMed, CINHAL, Embase, Scopus, Google Scholar and Web of Science were searched. Full-text research articles published in English from 1985 to February 2020 with cohort and cross-sectional studies design and reported an association between obesity and GDM were included. Case-control studies, case reports, conference abstract, women with previous metabolic disorders and articles considered general obesity only were excluded. A bias adjusted-quality effect meta-analysis was conducted to evaluate the association of these obesity phenotypes and GDM risk.

RESULTS

Twenty studies met the inclusion criteria representing data of ∼50 thousand women at the reproductive age with ∼7% prevalence of GDM. Meta-analysis of 14 datasets revealed that the three types of obesity were significantly associated with an increased risk of GDM. In addition, visceral adiposity was a stronger risk factor for GDM than other obesity phenotypes (odd ratio = 3.25, 95% confidence interval = 2.01-5.26) versus (odd ratio = 2.73, 95% confidence interval = 2.20-3.38) for general obesity and (odd ratio = 2.53, 95% confidence interval = 2.04-3.14) for central obesity.

CONCLUSION

The findings of this study suggest that general obesity, central obesity and visceral body fat were associated with an increased risk of GDM. Furthermore, the association with maternal visceral adiposity was more robust compared to general obesity and central obesity.

Prospective observational investigation of body habitus measurements and relationship to epidural depth in term pregnant women

BACKGROUND

High body mass index (BMI) can predict difficult neuraxial block; however, fat distribution may also be important. The primary study aim was to identify body habitus and fat distribution measurements that correlated with ultrasound measured epidural depth. We hypothesized that measurements such as midarm and subscapular fatpad thicknesses and length of cervical spine may correlate better with ultrasound measured epidural depth than a global measure of BMI.

METHODS

Prospective IRB approved study of term pregnant women requiring neuraxial block. We measured height, weight (BMI, kg/m² ), subscapular, midarm fatpad thickness (digital caliper, mm), vertebral column length (C7 to sacral hiatus, cm) and epidural depth (ultrasound, mm). Four experts assessed photographs to assign anticipated difficult neuraxial block in sitting and lateral positions (5-point Likert scale, 1 = very easy, 5 = very difficult).

RESULTS

In all, 131 women completed body habitus measurements. Measured mean (standard deviation) BMI was 30.3 (5.4) kg/m² . Measured BMI, subscapular fatpad and midarm fatpad thickness were significantly correlated with ultrasound depth to epidural space (R² 0.733, 0.626 and 0.633, respectively, P < .0001) but vertebral column length was not. The experts had a high level of agreement (Cronbach's alpha >0.7) for assessment of anticipated difficult block in the sitting and lateral positions; however, anticipated difficult block was not correlated with epidural depth measured by ultrasound for sitting position, R²  = -0.015, P = .87; and lateral position, R²  = -0.087, P = .33.

CONCLUSIONS

Measurements of body habitus and fat distribution were no better than measured BMI to anticipate greater ultrasound measured depth to epidural space. Clinical trial number: Non-interventional observational study, not registered.

Maternal Adipose Tissue Expansion, A Missing Link in the Prediction of Birth Weight Centile

CONTEXT

Maternal body mass index (BMI) is associated with increased birth weight but does not explain all the variance in fetal adiposity.

OBJECTIVE

To assess the contribution of maternal body fat distribution to offspring birth weight and adiposity.

DESIGN

Longitudinal study throughout gestation and at delivery.

SETTING

Women recruited at 12 weeks of gestation and followed up at 26 and 36 weeks. Cord blood was collected at delivery.

PATIENTS

Pregnant women (n = 45) with BMI 18.0 to 46.3 kg/m2 and healthy pregnancy outcome.

METHODS

Maternal first trimester abdominal subcutaneous and visceral adipose tissue thickness (SAT and VAT) was assessed by ultrasound.

MAIN OUTCOME MEASURES

Maternal body fat distribution, maternal and cord plasma glucose and lipid concentrations, placental weight, birth weight, and fetal adiposity assessed by cord blood leptin.

RESULTS

VAT was the only anthropometric measure independently associated with birth weight centile (r2 adjusted 15.8%, P = .002). BMI was associated with trimester 2 and trimesters 1 through 3 area under the curve (AUC) glucose and insulin resistance (Homeostatic Model Assessment). SAT alone predicted trimester 2 lipoprotein lipase (LPL) mass (a marker of adipocyte insulin sensitivity) (11.3%, P = .017). VAT was associated with fetal triglyceride (9.3%, P = .047). Placental weight was the only independent predictor of fetal adiposity (48%, P < .001). Maternal trimester 2 and AUC LPL were inversely associated with fetal adiposity (r = -0.69, P = .001 and r = -0.58, P = .006, respectively).

CONCLUSIONS

Maternal VAT provides additional information to BMI for prediction of birth weight. VAT may be a marker of reduced SAT expansion and increased availability of maternal fatty acids for placental transport.

How polluted is your fat? What the study of adipose tissue can contribute to environmental epidemiology

The study of the potential contribution of low-dose exposure to environmental chemicals on the development of chronic conditions in human populations is often hampered by methodological issues, including exposure misclassification and the inability to assess biological effects in target organs. White adipose tissue (WAT) presents the unique feature of being both an advantageous matrix for assessing long-term exposure to mixtures of persistent organic pollutants and an interesting tissue to investigate early preclinical effects. Moreover, other lipophilic non-persistent chemicals and heavy metals have been recently quantified in fat, suggesting that human WAT contains chemical mixtures more complex than initially thought. However, WAT has been scarcely used in environmental epidemiology due to collection difficulties. In this essay we discuss the potential of using human WAT as a source of both exposure and effect biomarkers, with the aim of advancing the epidemiological research of obesity-related diseases, including metabolic syndrome and cancer. Overall, we discuss the implications of investigating WAT in a multidisciplinary framework combining toxicological and epidemiological knowledge in order to improve the inference of causal relationships in observational settings. We finalise by suggesting feasible designs and scenarios in which WAT samples may be reasonably collected.

Difference in Visceral Adipose Tissue in Pregnancy and Postpartum and Related Changes in Maternal Insulin Resistance

OBJECTIVE

To measure the difference between first-trimester and postpartum visceral adipose tissue (VAT), the agreement of this difference with change in body mass index, and whether a difference in VAT is associated with insulin resistance or glucose mishandling.

METHODS

Prospective study of 93 women with singleton pregnancies without a history of diabetes. Visceral adipose tissue depth was sonographically assessed at 11 to 14 weeks and at 6 to 12 weeks postpartum. Metabolic measures, sampled at 24 to 28 weeks and 6 to 12 weeks postpartum, included homeostatic model assessment of insulin resistance, insulin sensitivity index composite, and area under the 75-g oral glucose tolerance test curve.

RESULTS

First-trimester VAT depth explained only 37% (95% confidence interval [CI], 22-52) of the variation in postpartum VAT depth. There was limited agreement between the net change in postpartum minus first-trimester VAT depth and that same net change for body mass index (Cohen's kappa, 0.26; 95% CI, 0.05-0.47). Those with a net gain in VAT depth demonstrated poorer insulin sensitivity index postpartum than women with a net regression in VAT depth-a difference of -2.0 (95% CI, -3.3 to -0.69).

CONCLUSION

Sonographic assessment of postpartum VAT is feasible and may provide insight to metabolic changes between pregnancy and postpartum, beyond body mass index.

Increasing body mass index and abdominal subcutaneous fat thickness are associated with increased skin-to-epidural space distance in pregnant women

BACKGROUND

Body mass index does not indicate the distribution of adipose tissue. Central adiposity may be measured using ultrasound measurement of subcutaneous fat thickness. This study determined if the abdominal subcutaneous fat thickness measured correlated with skin-to-epidural space distance at delivery, and compared this with the booking body mass index.

METHODS

We analysed a sub-set of participants from a single-centre, prospective cohort study that assessed the relationship between subcutaneous fat thickness and maternity outcomes. Abdominal subcutaneous fat thickness measurements were obtained during the routine fetal anomaly scan. The skin-to-epidural space distance was obtained in those having epidural or combined spinal-epidural analgesia. Linear regression was used to test for strength of association and adjusted R² values calculated to determine if subcutaneous fat thickness or body mass index was more strongly associated with skin-to-epidural space distance.

RESULTS

The 463 women had a median (IQR) booking body mass index of 25.0 kg/m² (21.8-29.3) and subcutaneous fat thickness of 16.2 mm (13.0-21.0). The median (IQR) skin-to-epidural space distance was 5.0 cm (4.5-6.0). Both parameters significantly correlated with skin-to-epidural space distance (r=0.53 and 0.68 respectively, P <0.001). Adjusted linear regression coefficient (95% CI) for subcutaneous fat thickness was 0.09 (0.08 to 0.11), R²=0.30 and for body mass index 0.12 (0.11 to 0.13), R²=0.47.

CONCLUSIONS

Booking body mass index had a stronger relationship with skin-to- epidural space distance at delivery than subcutaneous fat thickness, explaining 47% of the variation in the skin-to-epidural distance.

Anthropometric and ultrasound measures of maternal adiposity in the first trimester of pregnancy

Aim

Estimations of central adiposity in pregnancy is a difficult undertaking due to physiological changes that occur in the body. Therefore, the value of some anthropometric measures particularly in pregnancy, such as body mass index (BMI), waist and hip measures are in doubt. The aim was to compare ultrasound (US) measured abdominal subcutaneous fat (USSFT) with other simple anthropometric methods for obesity assessment, evaluating these measures in pregnancy.

Method

Recruited from a larger study, anthropometric measurements were performed between 11-14 weeks' gestation on 575 women. Measuring height, weight, hip, waist circumference, skin-folds of the triceps, thigh and supra-iliac and USSFT. Percentage maternal fat mass was calculated using skin-fold measures. Correlations of these measures were performed to gauge relationships.

Results

The anthropometric measures demonstrated good correlation (0.54-0.93) between individual adipose measures skin-folds, waist, hip, waist to height ratio (WSR) and USSFT with BMI, percentage fat mass and weight. USSFT correlated well with all anthropometric measures (0.54-0.73) correlating best with waist, WSR, BMI and weight. Waist/hip ratio demonstrated a poor correlation with USSFT, BMI, percentage fat mass and weight (0.3-0.41). Mean anthropometric measures were stratified across BMI categories describing adiposity distribution.

Conclusion

USSFT correlates well with most anthropometric measures in early pregnancy. Limitations of the gravid uterus on waist measurements, hydration and compressibility of skin-fold measures and pregnancy influences on weight and BMI assessments could be overcome using US measures. There is a potential for post hoc evaluation using US for pregnancy complications. Maternal research could benefit from a more accurate measure of adiposity.