Maternal pelvic dimensions and neonatal size: Implications for growth plasticity in early life as adaptation

Reconsidering the developmental origins of adult disease paradigm: The 'metabolic coordination of childbirth' hypothesis

In uncomplicated pregnancies, birthweight is inversely associated with adult non-communicable disease (NCD) risk. One proposed mechanism is maternal malnutrition during pregnancy. Another explanation is that shared genes link birthweight with NCDs. Both hypotheses are supported, but evolutionary perspectives address only the environmental pathway. We propose that genetic and environmental associations of birthweight with NCD risk reflect coordinated regulatory systems between mother and foetus, that evolved to reduce risks of obstructed labour. First, the foetus must tailor its growth to maternal metabolic signals, as it cannot predict the size of the birth canal from its own genome. Second, we predict that maternal alleles that promote placental nutrient supply have been selected to constrain foetal growth and gestation length when fetally expressed. Conversely, maternal alleles that increase birth canal size have been selected to promote foetal growth and gestation when fetally expressed. Evidence supports these hypotheses. These regulatory mechanisms may have undergone powerful selection as hominin neonates evolved larger size and encephalisation, since every mother is at risk of gestating a baby excessively for her pelvis. Our perspective can explain the inverse association of birthweight with NCD risk across most of the birthweight range: any constraint of birthweight, through plastic or genetic mechanisms, may reduce the capacity for homeostasis and increase NCD susceptibility. However, maternal obesity and diabetes can overwhelm this coordination system, challenging vaginal delivery while increasing offspring NCD risk. We argue that selection on viable vaginal delivery played an over-arching role in shaping the association of birthweight with NCD risk.

The developmental impacts of natural selection on human pelvic morphology

Evolutionary responses to selection for bipedalism and childbirth have shaped the human pelvis, a structure that differs substantially from that in apes. Morphology related to these factors is present by birth, yet the developmental-genetic mechanisms governing pelvic shape remain largely unknown. Here, we pinpoint and characterize a key gestational window when human-specific pelvic morphology becomes recognizable, as the ilium and the entire pelvis acquire traits essential for human walking and birth. We next use functional genomics to molecularly characterize chondrocytes from different pelvic subelements during this window to reveal their developmental-genetic architectures. We then find notable evidence of ancient selection and genetic constraint on regulatory sequences involved in ilium expansion and growth, findings complemented by our phenotypic analyses showing that variation in iliac traits is reduced in humans compared to African apes. Our datasets provide important resources for musculoskeletal biology and begin to elucidate developmental mechanisms that shape human-specific morphology.

Food taboos during pregnancy: meta-analysis on cross cultural differences suggests specific, diet-related pressures on childbirth among agriculturalists

Pregnancy is the most delicate stage of human life history as well as a common target of food taboos across cultures. Despite puzzling evidence that many pregnant women across the world reduce their intake of nutritious foods to accomplish cultural norms, no study has provided statistical analysis of cross-cultural variation in food taboos during pregnancy. Moreover, antenatal practices among forager and agriculturalists have never been compared, despite subsistence mode being known to affect staple foods and lifestyle directly. This gap hinders to us from understanding the overall threats attributed to pregnancy, and their perceived nutritional causes around the world. The present study constitutes the first cross-cultural meta-analysis on food taboos during pregnancy. We examined thirty-two articles on dietary antenatal restrictions among agricultural and non-agricultural societies, in order to: (i) identify cross-culturally targeted animal, plant and miscellaneous foods; (ii) define major clusters of taboo focus; (iii) test the hypothesis that food types and clusters of focus distribute differently between agricultural and non-agricultural taboos; and (iv) test the hypothesis that food types distribute differently across the clusters of taboo focus. All data were analysed in SPSS and RStudio using chi-squared tests and Fisher's exact tests. We detected a gradient in taboo focus that ranged from no direct physiological interest to the fear of varied physiological complications to a very specific concern over increased birth weight and difficult delivery. Non-agricultural taboos were more likely to target non-domesticated animal foods and to be justified by concerns not directly linked to the physiological sphere, whereas agricultural taboos tended to targed more cultivated and processed products and showed a stronger association with concerns over increased birth weight. Despite some methodological discrepancies in the existing literature on food taboos during pregnancy, our results illustrate that such cultural traits are useful for detecting perception of biological pressures on reproduction across cultures. Indeed, the widespread concern over birth weight and carbohydrate rich foods overlaps with clinical evidence that obstructed labor is a major threat to maternal life in Africa, Asia and Eurasia. Furthermore, asymmetry in the frequency of such concern across subsistence modes aligns with the evolutionary perspective that agriculture may have exacerbated delivery complications. This study highlights the need for the improved understanding of dietary behaviors during pregnancy across the world, addressing the role of obstructed labor as a key point of convergence between clinical, evolutionary and cultural issues in human behavior.

Birth length is the strongest predictor of linear growth status and stunting in the first 2 years of life after a preconception maternal nutrition intervention: the children of the Women First trial

BACKGROUND

The multicountry Women First trial demonstrated that nutritional supplementation initiated prior to conception (arm 1) or early pregnancy (arm 2) and continued until delivery resulted in significantly greater length at birth and 6 mo compared with infants in the control arm (arm 3).

OBJECTIVES

We evaluated intervention effects on infants' longitudinal growth trajectory from birth through 24 mo and identified predictors of length status and stunting at 24 mo.

METHODS

Infants' anthropometry was obtained at 6, 12, 18, and 24 mo after the Women First trial (registered at clinicaltrials.gov as NCT01883193), which was conducted in low-resource settings: Democratic Republic of Congo, Guatemala, India, and Pakistan. Longitudinal models evaluated intervention effects on infants' growth trajectory from birth to 24 mo, with additional modeling used to identify adjusted predictors for growth trajectories and outcomes at 24 mo.

RESULTS

Data for 2337 (95% of original live births) infants were evaluated. At 24 mo, stunting rates were 62.8%, 64.8%, and 66.3% for arms 1, 2, and 3, respectively (NS). For the length-for-age z-score (LAZ) trajectory, treatment arm was a significant predictor, with adjusted mean differences of 0.19 SD (95% CI: 0.08, 0.30; P < 0.001) and 0.17 SD (95% CI: 0.07, 0.27; P < 0.001) for arms 1 and 2, respectively. The strongest predictors of LAZ at 24 mo were birth LAZ <-2 and <-1 to ≥-2, with adjusted mean differences of -0.76 SD (95% CI: -0.93, -0.58; P < 0.001) and -0.47 SD (95% CI: -0.56, -0.38; P < 0.001), respectively. For infants with ultrasound-determined gestational age (n = 1329), the strongest predictors of stunting were birth LAZ <-2 and <-1 to ≥- 2: adjusted relative risk of 1.62 (95% CI: 1.39, 1.88; P < 0.001) and 1.46 (95% CI: 1.31, 1.62; P < 0.001), respectively.

CONCLUSIONS

Substantial improvements in postnatal growth are likely to depend on improved intrauterine growth, especially during early pregnancy.

Differential relationships between parent-child DXA and pQCT bone measures: Results from the Southampton Women's Survey

AIM

To investigate the associations between indices of bone health in childhood and corresponding parental measures.

METHODS

The Southampton Women's Survey characterised 12,583 non-pregnant women aged 20-34 years; 3158 subsequently had singleton live births. In a subset, dual-energy X-ray absorptiometry (DXA) measurements of bone area (BA), bone mineral content (BMC) and areal bone mineral density (aBMD) lumbar spine and total hip were obtained in the parent/offspring (aged 8-9 years) trios. Another subset of children (aged 6-7 years), and their parents, had peripheral quantitative computed tomography (pQCT; 4% and 38% tibia) measures. Using multivariable linear regression we examined relationships between mother/father and offspring, adjusting for parental age, habitual walking speed and education; offspring age and sex; and the corresponding bone measure in the other parent (β-coefficients (95%CI) unit/unit for each bone measure).

RESULTS

Data were available for 260 trios with DXA and 99 with pQCT. There were positive associations for BA, BMC and aBMD between either parent and offspring. Mother-child associations were of greater magnitude than father-child; for example, mother-child aBMD (β = 0.26 g·cm-2/g·cm-2 (0.21,0.32)) and father-child aBMD (β = 0.16 g·cm-2/g·cm-2 (0.11,0.21)), P-difference in β = 0.007. In the subset with pQCT there was a positive association for mother-offspring 4% tibial total area (β = 0.33 mm2/mm2 (0.17,0.48)), but little evidence of a father-offspring association (β = -0.06 mm2/mm2 (-0.17,0.06)). In contrast offspring 38% cortical density was more strongly associated with this measure in fathers (β = 0.48 mg·cm-3/mg·cm-3 (0.15,0.82)) than mothers (β = 0.27 mg·cm-3/mg·cm-3 (-0.03,0.56)). In general mother-father differences were attenuated by adjustment for height.

CONCLUSIONS

Whilst offspring bone measures are independently associated with those of either parent, the magnitude of the association is often greater for maternal than paternal relationships. These findings are consistent with an in utero influence on offspring growth but might also reflect genetic and/or epigenetic parent of origin effects.

SUMMARY

In an established parent-offspring cohort, associations between parent and offspring bone indices were generally greater in magnitude for mother-offspring than father-offspring relationships.

Evolution of Lactase Persistence: Turbo-Charging Adaptation in Growth Under the Selective Pressure of Maternal Mortality?

The emergence of the capacity to digest milk in some populations represents a landmark in human evolution, linking genetic change with a component of niche construction, namely dairying. Alleles promoting continued activity of the enzyme lactase through the life-course (lactase persistence) evolved in several global regions within the last 7,000 years. In some European regions, these alleles underwent rapid selection and must have profoundly affected fertility or mortality. Elsewhere, alleles spread more locally. However, the functional benefits underlying the rapid spread of lactase persistence remain unclear. Here, we set out the hypothesis that lactase persistence promoted skeletal growth, thereby offering a generic rapid solution to childbirth complications arising from exposure to ecological change, or to new environments through migration. Since reduced maternal growth and greater neonatal size both increase the risk of obstructed labour, any ecological exposure impacting these traits may increase maternal mortality risk. Over many generations, maternal skeletal dimensions could adapt to new ecological conditions through genetic change. However, this adaptive strategy would fail if ecological change was rapid, including through migration into new niches. We propose that the combination of consuming milk and lactase persistence could have reduced maternal mortality by promoting growth of the pelvis after weaning, while high calcium intake would reduce risk of pelvic deformities. Our conceptual framework provides locally relevant hypotheses to explain selection for lactase persistence in different global regions. For any given diet and individual genotype, the combination of lactase persistence and milk consumption would divert more energy to skeletal growth, either increasing pelvic dimensions or buffering them from worsening ecological conditions. The emergence of lactase persistence among dairying populations could have helped early European farmers adapt rapidly to northern latitudes, East African pastoralists adapt to sudden climate shifts to drier environments, and Near Eastern populations counteract secular declines in height associated with early agriculture. In each case, we assume that lactase persistence accelerated the timescale over which maternal skeletal dimensions could change, thus promoting both maternal and offspring survival. Where lactase persistence did not emerge, birth weight was constrained at lower levels, and this contributes to contemporary variability in diabetes risk.

Comparing the pelvis of Tibetan and Chinese Han women in rural areas of China: two population-based studies using coarsened exact matching

This study aims to investigate the difference of pelvic size and shape between Tibetan and Chinese Han women. Data on pelvic dimension measures including interspinous diameter (IS), intercrestal diameter (IC), external conjugate (EC) and transverse outlet (TO) were acquired from two population-based studies amongst Tibetan women in Lhasa, and Chinese Han women in Shaanxi province in China. After coarsened exact matching, there was no statistical difference between any characteristics amongst Tibetan and Chinese Han women (p>.05). The generalised estimating equation models showed Tibetan women had significantly lower IS and IC means than Chinese Han women (IS: 24.39 cm vs. 24.77 cm, p<.001; IC: 26.35 cm vs. 26.93 cm, p<.001) but statistically higher in TO mean (9.12 cm vs. 9.03 cm, p<.001). This study showed Tibetan women have smaller pelvis compared to Chinese Han women. This should offer a useful literature on the comparison of pelvis between Tibetan and Chinese Han women although the difference is small.Impact StatementWhat is already known on this subject? Previous studies in China indicated different populations have different dimensions of pelvis, with the pelvis of Uighur women being bigger than Chinese Han women, and that of Zhuang and Tu women being smaller than Chinese Han women. Little research reports the specific size of Tibetan women's pelvis. Living at high altitude, the Tibetan population have differentiated demographics and show local adaptions, such as unelevated haemoglobin, and significant catch-up growth for infants compared with Chinese Han infants. Therefore, there is a strong rationale for better understanding pelvic characteristics amongst this population.What the results of this study add? This study showed Tibetan women have smaller pelvises compared to Chinese Han women. Tibetan women have a smaller interspinous diameter and intercrestal diameter than Chinese Han women, which leads to relatively narrow hip.What the implications are of these findings for clinical practice and/or further research? This study provides useful comparative information on pelvic features between Tibetan and Chinese Han women although the findings of differences were small. In addition, during the formulation of women's health policy, the results of this study can provide data to support the selection of appropriate indicators of obstetrics and gynaecology for different populations of pregnant women during antenatal care and delivery.

Pelvic and neonatal size correlations in light of evolutionary hypotheses

OBJECTIVE

This study aimed to analyze the correlations between maternal size, neonatal size, and gestational variables.

METHODS

Our sample comprises 131 mother-infant dyads. We investigated correlations between five neonatal traits (gestational age, birthweight, head, suboccipito-brematic, and abdominal girths), three maternal traits (height, BMI, and uterus height), and three pelvic variables (conjugate, inter-spinous diameters, and sub-pubic angle) using computed tomography pelvimetry.

RESULTS

We found that the five neonatal traits were significantly intercorrelated. BMI was not correlated with neonatal traits while maternal height was correlated with birthweight, suboccipito-brematic, and abdominal girth. In the multiple regression models, gestational age was correlated with birthweight, head, and abdominal girth. Among the neonatal and pelvimetry correlations, conjugate diameter was slightly correlated with suboccipito-bregmatic girth, but inter-spinous and sub-pubic angle were not correlated with neonatal traits. Uterus height predicted all neonatal variables, but it was not correlated with gestational age.

DISCUSSION

Our results suggest that fetal growth is shaped by maternal phenotype rather than external ecological factors. The association of the inlet size with suboccipito-bregmatic girth reflects the tight fit between the neonatal brain and the maternal pelvis dimensions, an adaptation that would reduce the risk of cephalo-pelvic disproportion, while the absence of tight fit at the midplane and outlet could be due to the effect of the pelvic relaxation. Uterus distention is not the only mechanism involved in the initiation of parturition. Birth and pregnancy are complex processes and we suggest that maternal-neonatal associations are the result of a combination of multiple obstetric tradeoffs.

Maternal physical, socioeconomic, and demographic characteristics and childbirth complications in rural lowland Nepal: Applying an evolutionary framework to understand the role of phenotypic plasticity

OBJECTIVES

Evolutionary perspectives on human childbirth have primarily focused on characteristics of our species in general, rather than variability within and between contemporary populations. We use an evolutionary framework to explore how physical and demographic characteristics of mothers shape the risks of childbirth complications in rural lowland Nepal, where childbearing typically commences in adolescence and chronic undernutrition is widespread, though maternal overweight is increasing in association with nutrition transition.

METHODS

We conducted secondary analyses of data from a cluster-randomized trial. Women aged 14-35 years were categorized by age, number of previous pregnancies, height, body mass index (BMI), husband's education, and household wealth. Multivariable logistic regression models tested whether these characteristics independently predicted risks of episiotomy and cesarean section (CS, n = 14 261), and obstructed labor (OL, n = 5185).

RESULTS

Risks were greatest among first-time adolescent mothers, though associations with age varied by outcome. Independent of age and parity, short stature and high BMI increased risks of CS and OL, whereas associations were weaker for episiotomy. Male offspring had increased risk of CS and OL but not episiotomy. Wealth was not associated with OL, but lower wealth and lower husband's education were associated with lower likelihood of episiotomy and CS.

CONCLUSIONS

At the individual level, the risk childbirth complications is shaped by trade-offs between fertility, growth, and survival. Some biological markers of disadvantage (early childbearing, short stature) increased the risk, whereas low socio-economic status was associated with lower risk, indicating reduced access to relevant facilities. Independent of these associations, maternal age showed complex effects.

Obstetric dimensions of the female pelvis are less integrated than locomotor dimensions and show protective scaling patterns: Implications for the obstetrical dilemma

OBJECTIVES

The "obstetrical dilemma" hypothesis assumes that the modern human female pelvis serves two discrete functions: obstetrics and locomotion. We investigate whether these differing functions create observable patterns of morphological covariation and whether those patterns differ by height, weight, and age. This allows evaluation of evidence for canalization and phenotypic plasticity relevant to obstetric and locomotor function among a living female population.

METHODS

Landmarks (N = 86) were collected and inter-landmark distances were calculated (N = 36) on the pelvis and proximal femur of CT scans of living women aged 20 to 90 years (M = 93) receiving a routine CT scan. Partial least squares and relative SD of eigenvalues analyses were used to evaluate integration overall and within locomotor and obstetric modules, respectively. Ordinary Least Squared regression was used to evaluate scaling relationships between inter-landmark distances and height, weight, and age.

RESULTS

The obstetric pelvis was significantly less internally integrated than the locomotor pelvis. Many obstetric measurements were constrained in absolute terms relative to height; shorter women had relatively larger birth canal dimensions, and several key obstetric dimensions showed relative freedom from height. Lower weight women had some relatively larger obstetric and locomotor dimensions. Regarding age, younger women showed a few relatively larger outlet dimensions.

CONCLUSIONS

This study suggests that the obstetric pelvis and the locomotor pelvis function are morphologically distinct, with the obstetric pelvis showing relatively greater flexibility. These relationships between relative constraints support the hypothesis that the modern female pelvis shows evidence of both canalization and phenotypic plasticity in obstetric and locomotor structures.

The Maternal Nutritional Buffering Model: an evolutionary framework for pregnancy nutritional intervention

Evidence that fetal nutrition influences adult health has heightened interest in nutritional interventions targeting pregnancy. However, as is true for other placental mammals, human females have evolved mechanisms that help buffer the fetus against short-term fluctuations in maternal diet and energy status. In this review, we first discuss the evolution of increasingly elaborate vertebrate strategies of buffering offspring from environmental fluctuations during development, including the important innovation of the eutherian placenta. We then present the Maternal Nutritional Buffering Model, which argues that, in contrast to many micronutrients that must be derived from dietary sources, the effects of short-term changes in maternal macronutrient intake during pregnancy, whether due to a deficit or supplementation, will be minimized by internal buffering mechanisms that work to ensure a stable supply of essential resources. In contrast to the minimal effects of brief macronutrient supplementation, there is growing evidence that sustained improvements in early life and adult pre-pregnancy nutrition could improve birth outcomes in offspring. Building on these and other observations, we propose that strategies to improve fetal macronutrient delivery will be most effective if they modify the pregnancy metabolism of mothers by targeting nutrition prior to conception and even during early development, as a complement to the conventional focus on bolstering macronutrient intake during pregnancy itself. Our model leads to the prediction that birth weight will be more strongly influenced by the mother’s chronic pre-pregnancy nutrition than by pregnancy diet, and highlights the need for policy solutions aimed at optimizing future, intergenerational health outcomes.

Lay summary: We propose that strategies to improve fetal macronutrient delivery will be most effective if they modify the pregnancy metabolism of mothers by targeting nutrition prior to conception and even during early development, as a complement to the conventional focus on bolstering macronutrient intake during pregnancy itself.

Secular Dynamics of Body Height and Weight in Russian Children Aged 0–17

This study deals with long-term temporal changes of body height and weight during various stages of ontogeny: newborns, infancy, early age, fi rst childhood, second childhood, adolescence, and youth. Each age/sex group numbers ca 100 persons, the total sample size is ca 2 000. The meta-analysis is based primarily on growth standards for Russian children, regularly renewed by the Research Institute for the Hygiene and Health Protection of Children and Adolescents and mostly relating to separate decades of the 20th century. The intensity of the secular trends was assessed through the analysis of scatter plots. The largest share in the secular increase of bodily dimensions belongs to intense growth during the second year of life and during the adolescent growth spurt. The smallest share is that of intrauterine growth, limited by the mother’s body size, and that of growth during adolescence, when the mature body size has been virtually reached and growth rate is minimal. Boys, who are more eco-sensitive, demonstrate greater secular changes than girls, who are eco-resistant. Smaller secular changes in weight than in height in both boys and girls result in the increase of leptosomy. This heterochrony concerns mostly newborns, whose body mass is a standard example of stabilizing selection.

Intrapartum prediction of birth weight with a simplified algorithmic approach derived from maternal characteristics

Objective To derive and validate a population-specific multivariate approach for birth weight (BW) prediction based on quantitative intrapartum assessment of maternal characteristics by means of an algorithmic method in low-risk women. Methods The derivation part (n = 200) prospectively explored 10 variables to create the best-fit algorithms (70% correct estimates within ±10% of actual BW) for prediction of BW at term; vertex presentation with engagement. The algorithm was then cross validated with samples of unrelated cases (n = 280) to compare the accuracy with the routine abdominal palpation method. Results The best-fit algorithms were parity-specific. The derived simplified algorithms were (1) BW (g) = 100 [(0.42 × symphysis-fundal height (SFH; cm)) + gestational age at delivery (GA; weeks) - 25] in nulliparous, and (2) BW (g) = 100 [(0.42 × SFH (cm)) + GA - 23] in multiparous. Cross validation showed an overall 69.3% accuracy within ±10% of actual BW, which exceeded routine abdominal palpation (60.4%) (P = 0.019). The algorithmic BW prediction was significantly more accurate than routine abdominal palpation in women with the following characteristics: BW 2500-4000 g, multiparous, pre-pregnancy weight <50 kg, current weight <60 kg, height <155 cm, body mass index (BMI) <18.5 kg/m2, cervical dilatation 3-5 cm, station <0, intact membranes, SFH 30-39 cm, maternal abdominal circumference (mAC) <90 cm, mid-upper arm circumference (MUAC) <25 cm and female gender of the neonates (P < 0.05). Conclusion An overall accuracy of term BW prediction by our simplified algorithms exceeded that of routine abdominal palpation.

Advanced glycation end products and adipocytokines and oxidative stress in placental tissues of pregnant women with gestational diabetes mellitus

Correlation between expression levels of advanced glycation end products (AGEs) and adipocytokines and oxidative stress index malondialdehyde (MDA) in placental tissues of pregnant women with gestational diabetes mellitus (GDM) was investigated. Seventy-two cases of GDM pregnant women who received routine prenatal examination and gave birth in the Department of Obstetrics, Binzhou City Center Hospital from March 2016 to May 2017 were collected as the observation group. Another 80 cases of normal pregnant women who gave birth at the same time were selected as the control group. Enzyme linked immunosorbent assay (ELISA) was used to detect the expression levels of AGEs, visfatin, APN and IL-6 in the lysate of placental tissues. MDA levels were measured by thiobarbituric acid method. Correlation of expression levels of AGEs, visfatin, APN, IL-6 and MDA were analyzed. The expression level of MDA in placental tissues of the observation group was significantly higher than that of the control group (t=16.44, P<0.001). The correlation of expression levels between AGEs, adipocytokines and MDA in placental tissues of the two groups was analyzed, and it was found that the expression levels of AGEs, visfatin and IL-6 in the two groups were positively correlated with MDA. There was a significantly negative correlation between APN and MDA in the two groups. The incidence of cesarean section, neonatal hypoglycemia, fetal distress and macrosomia in the observation group was significantly higher than that in the control group (P<0.05). There was no significant difference in the incidence of membrane rupture and premature birth between the two groups (P>0.05). In conclusion, the expression levels of AGEs, visfatin and IL-6 in placental tissues of GDM pregnant women are positively correlated with MDA. There is a significant negative correlation between APN and MDA, and they play an important role in the pathogenesis of GDM.

The Dual Burden of Malnutrition Increases the Risk of Cesarean Delivery: Evidence From India

Background: Among contemporary human populations, rates of cesarean delivery vary substantially, making it difficult to know if the procedure is inadequately available, or used excessively relative to medical need. A much-cited evolutionary hypothesis attributed birth complications to an “obstetric dilemma,” resulting from antagonistic selective pressures acting on maternal pelvic dimensions and fetal brain growth during hominin evolution. However, the childbirth challenges experienced by living humans may not be representative of those in the past, and may vary in association with trends in ecological conditions. We hypothesized that variability in maternal phenotype (height and nutritional status) may contribute to the risk of cesarean delivery. In many populations, high levels of child stunting contribute to a high frequency of short adult stature, while obesity is also becoming more common. The combination of short maternal stature and maternal overweight or obesity may substantially increase the risk of cesarean delivery.

Methods: Using data from two large Indian health surveys from 2005–6 to 2015–2016, we tested associations of maternal somatic phenotype (short stature, overweight) with the risk of cesarean delivery, adjusting for confounding factors such as maternal age, birth order, rural/urban location, wealth and offspring sex.

Results: Secular trends in maternal body mass index between surveys were greater than trends in height. Maternal short stature and overweight both increased the risk of cesarean delivery, most strongly when jointly present within individual women. These associations were independent of birth order, wealth, maternal age and rural/urban location. Secular trends in maternal phenotype explained 18% of the increase in cesarean rate over 10 years.

Conclusion: Our results highlight how the emerging dual burden of malnutrition (persisting short adult stature which reflects persistent child stunting; increasing overweight in adults) is likely to impact childbirth in low and middle-income countries.