Maternal Pelvic Size Research Articles

Sexual dimorphism in the size and shape of the non-obstetric pelvis across anthropoids.

The presence of sexual dimorphism in the birth canals of anthropoid primates is well documented, and birth canal dimorphism tends to be especially robust among species that give birth to relatively large neonates. However, it is less clear whether birth canal dimorphism is accompanied by dimorphism in parts of the pelvis not directly under selection for birth, particularly including bi-iliac breadth, biactetabular breadth, lengths of the ischium and ilium, and 3D shape. This study investigates the patterns of dimorphism among anthropoid primates in those parts of the pelvis which do not directly contribute to the bony birth canal, here termed the non-obstetric pelvis. 3D landmark data were collected on the bony pelves of 899 anthropoid primates. Specifically, landmark data were collected on parts of the pelvis not thought to be directly involved in selection for parturition, including portions of the posterior and superior ilium, acetabulum, and lateral ischium. Principal components analysis and Euclidean distance matrix analysis were used to ascertain sexual dimorphism in pelvic sizes and shapes within each species. Results show that dimorphism in non-obstetric pelvic size and shape exists across anthropoids, just as is seen in the birth canal. However, the magnitude of dimorphism in non-obstetric pelvic shape tends to be greater among anthropoid species that give birth to relatively large neonates compared with those birthing smaller neonates relative to maternal pelvic size. Though all anthropoids included in the study show some degree of sexual dimorphism in non-obstetric pelvic size and/or shape, species which give birth to large neonates relative to maternal pelvic size have the highest levels of dimorphism in pelvic shape. Moreover, the magnitude of dimorphism in certain parts of the non-obstetric pelvis mirrors patterns seen in the birth canal. The results of this study are promising for ascertaining pelvic dimorphism and relative neonate size in fossil primates, particularly in fragmentary remains which do not preserve a complete bony birth canal.

Does obstetric protection apply to small-bodied females?: A comparison between small-bodied Jomon foragers and large-bodied Yayoi agriculturalists in the prehistoric Japanese archipelago.

This study examined the relationship between maternal pelvic and body size in the transition from the Middle-Final Jomon period (c. 5000-3000 BC) to the Middle Yayoi period (c. 400~200 BC to around AD 1) in Japan. Eight measurements, including the left hip bone, articulated pelvis, and femur, were taken from Jomon (females: 37, males: 26) and Yayoi skeletal remains (females: 32, males: 29). A statistically significant decrease in the anterior diameter of the true pelvic inlet was demonstrated in females from the Jomon to the Yayoi period, but not in males. While significant increases in stature from the Jomon to the Yayoi period were found in both males and females, no significant changes in body mass were seen. The correlation coefficients between true and false pelvic measurements (maximum pelvic height and maximum pelvic breadth) and body size (stature and body mass) suggested few significant relationships between true and false pelvic measurements or body size among the samples, but no significant correlations in small-bodied Jomon females. Results of principal component analysis using the log-size and log-shape variables suggested that the true pelvic size in Jomon and Yayoi females was not correlated with their general pelvic or body size, and there were correlations between sexually dimorphic aspects of true pelvis shape and either the false pelvis or body size in males but not females. These results suggest that the obstetrical dimensions in small-bodied Jomon females were maintained for obstetric needs.

Maternal pelvic size, fetal growth and risk of stroke in adult offspring in a large Swedish cohort.

Earlier research suggests that maternal pelvic size is associated with offspring's stroke risk in later life. We followed 6362 men and women from Uppsala, Sweden, born between 1915 and 1929 from 1964 to 2008 to assess whether maternal pelvic size was associated with incidence of thrombotic stroke (TS), haemorrhagic stroke (HS) and other stroke (OS). Offspring whose mothers had a flat pelvis had lower birth weight and birth-weight-for-gestational-age compared with those who did not. Inverse linear associations of birth-weight-for-gestational-age were observed with TS and OS. Female offspring whose mothers had a flat pelvis had increased risk of TS, but flat pelvis was not associated with other types of stroke. A smaller difference between intercristal and interspinous diameters and a smaller external conjugate diameter were independently associated with HS, whereas no pelvic measurements were associated with OS. We conclude that a smaller pelvis in women may impact the health of their offspring in adulthood.

A wider pelvis does not increase locomotor cost in humans, with implications for the evolution of childbirth.

The shape of the human female pelvis is thought to reflect an evolutionary trade-off between two competing demands: a pelvis wide enough to permit the birth of large-brained infants, and narrow enough for efficient bipedal locomotion. This trade-off, known as the obstetrical dilemma, is invoked to explain the relative difficulty of human childbirth and differences in locomotor performance between men and women. The basis for the obstetrical dilemma is a standard static biomechanical model that predicts wider pelves in females increase the metabolic cost of locomotion by decreasing the effective mechanical advantage of the hip abductor muscles for pelvic stabilization during the single-leg support phase of walking and running, requiring these muscles to produce more force. Here we experimentally test this model against a more accurate dynamic model of hip abductor mechanics in men and women. The results show that pelvic width does not predict hip abductor mechanics or locomotor cost in either women or men, and that women and men are equally efficient at both walking and running. Since a wider birth canal does not increase a woman’s locomotor cost, and because selection for successful birthing must be strong, other factors affecting maternal pelvic and fetal size should be investigated in order to help explain the prevalence of birth complications caused by a neonate too large to fit through the birth canal.

Fetal pelvic index to predict cephalopelvic disproportion – a retrospective clinical cohort study

To investigate the diagnostic accuracy of the fetal pelvic index to predict cephalopelvic disproportion. Retrospective observational cohort study. Pregnant women who had been examined by X-ray or magnetic resonance imaging pelvimetry because of an increased risk of fetal-pelvic disproportion during 2000-2008 in North Karelia Central Hospital. A total of 274 pregnant women. Univariable and multivariable regression analyses were carried out to identify risk factors for cesarean section. Diagnostic accuracy was tested with a receiver operating characteristic curve, and the optimal cut-off value for fetal pelvic index was calculated. Cesarean section rates. A total of 242 women delivered vaginally, and 32 delivered with cesarean section caused by labor arrest. In multivariable modeling, the fetal pelvic index, maternal pelvic inlet size, fetal head circumference and maternal age were significantly associated with a risk of cesarean section. In the receiver operating characteristic analysis, the area under curve was 0.686 with a p-value of 0.001 and a 95% confidence interval of 0.595-0.778. The optimal fetal pelvic index cut-off value according to the receiver operating characteristic was -0.65. The cesarean section rate was 8% below the fetal pelvic index value of -0.65 and 20% above the fetal pelvic index value of -0.65. The fetal pelvic index was not a clinically useful tool to predict the mode of delivery for patients at high risk of cephalopelvic disproportion. The pooled analysis of the current and previous studies strengthened this conclusion.

An investigation of factors identified at birth in relation to anxiety and depression in old age: the Hordaland Health Study (HUSK).

BackgroundAlthough life course influences have long been recognised in affective disorder, little is known about the influence of early life factors on late life anxiety and depression. The aim was to investigate the extent to which birth measures, maternal health and family circumstances were associated with symptoms of anxiety and depression in late life.MethodsA retrospective cohort study was constructed from a cross-sectional survey sample of community residents aged 72–74 years, 406 of whom had traceable birth records. Cases and controls for late life anxiety and depression were defined applying standard cut-offs to the Hospital Anxiety and Depression Scale. A range of measures and circumstances were extracted from birth records blind to survey data and compared in age- and gender-adjusted models.ResultsThere were no differences in any anthropometric measure in either case control comparison. Case-level anxiety and depression were both associated with significantly lower maternal age. Late-life anxiety was additionally associated with smaller maternal pelvic size and the mother’s condition being rated as poor at birth/discharge. Late-life depression was associated with a lower status paternal occupation.ConclusionsThere was no evidence for a substantial influence of early life size on late life affective disorder. However, there was some evidence in secondary analyses for an enduring influence of the family’s socioeconomic environment and maternal health.

The Effect of Pelvic Size on Cesarean Delivery Rates: Using Adolescent Maternal Age as an Unbiased Proxy for Pelvic Size

ObjectivesDystocia, the presence of abnormal labor, is the most common indication for cesarean delivery. Risk factors for dystocia include abnormalities of expulsatile forces during labor, fetal factors, and maternal pelvic size abnormalities. The objective of our study was to evaluate the effect of pelvic size on the risk of cesarean delivery rates using adolescent maternal age as an unbiased determinant of pelvic size. MethodsWe conducted a population-based cohort study using the Center for Disease Control and Prevention’s Linked Birth-Infant Death and Fetal Death data on all births in the US between 1995 and 2004 for women aged 12 to 20. We excluded all births of gestational age under 24 weeks and those with reported congenital malformations or chromosomal abnormalities. Maternal age and mode of delivery information was obtained from the birth records. ResultsThere were 6,188,704 births in our cohort of which 1,863 were to women aged 12; 12,903 to women aged 13; 68,890 to women aged 14, and the remainder to women aged 15 and above. Cesarean delivery rates were highest amongst women aged 12 at 19.59 % and declined to 13.92% amongst 15 year-olds, and 14.84 % amongst 20 year olds. This effect was more pronounced when the analysis was restricted to macrosomic fetuses (P<0.005). ConclusionCesarean delivery rates increase the younger the maternal age is suggesting that pelvic factors can play an important role in dystocia.

DNA sequence polymorphisms within the bovine guanine nucleotide-binding protein Gs subunit alpha (Gsα)-encoding (GNAS) genomic imprinting domain are associated with performance traits

BackgroundGenes which are epigenetically regulated via genomic imprinting can be potential targets for artificial selection during animal breeding. Indeed, imprinted loci have been shown to underlie some important quantitative traits in domestic mammals, most notably muscle mass and fat deposition. In this candidate gene study, we have identified novel associations between six validated single nucleotide polymorphisms (SNPs) spanning a 97.6 kb region within the bovine guanine nucleotide-binding protein Gs subunit alpha gene (GNAS) domain on bovine chromosome 13 and genetic merit for a range of performance traits in 848 progeny-tested Holstein-Friesian sires. The mammalian GNAS domain consists of a number of reciprocally-imprinted, alternatively-spliced genes which can play a major role in growth, development and disease in mice and humans. Based on the current annotation of the bovine GNAS domain, four of the SNPs analysed (rs43101491, rs43101493, rs43101485 and rs43101486) were located upstream of the GNAS gene, while one SNP (rs41694646) was located in the second intron of the GNAS gene. The final SNP (rs41694656) was located in the first exon of transcripts encoding the putative bovine neuroendocrine-specific protein NESP55, resulting in an aspartic acid-to-asparagine amino acid substitution at amino acid position 192.ResultsSNP genotype-phenotype association analyses indicate that the single intronic GNAS SNP (rs41694646) is associated (P ≤ 0.05) with a range of performance traits including milk yield, milk protein yield, the content of fat and protein in milk, culled cow carcass weight and progeny carcass conformation, measures of animal body size, direct calving difficulty (i.e. difficulty in calving due to the size of the calf) and gestation length. Association (P ≤ 0.01) with direct calving difficulty (i.e. due to calf size) and maternal calving difficulty (i.e. due to the maternal pelvic width size) was also observed at the rs43101491 SNP. Following adjustment for multiple-testing, significant association (q ≤ 0.05) remained between the rs41694646 SNP and four traits (animal stature, body depth, direct calving difficulty and milk yield) only. Notably, the single SNP in the bovine NESP55 gene (rs41694656) was associated (P ≤ 0.01) with somatic cell count--an often-cited indicator of resistance to mastitis and overall health status of the mammary system--and previous studies have demonstrated that the chromosomal region to where the GNAS domain maps underlies an important quantitative trait locus for this trait. This association, however, was not significant after adjustment for multiple testing. The three remaining SNPs assayed were not associated with any of the performance traits analysed in this study. Analysis of all pairwise linkage disequilibrium (r2) values suggests that most allele substitution effects for the assayed SNPs observed are independent. Finally, the polymorphic coding SNP in the putative bovine NESP55 gene was used to test the imprinting status of this gene across a range of foetal bovine tissues.ConclusionsPrevious studies in other mammalian species have shown that DNA sequence variation within the imprinted GNAS gene cluster contributes to several physiological and metabolic disorders, including obesity in humans and mice. Similarly, the results presented here indicate an important role for the imprinted GNAS cluster in underlying complex performance traits in cattle such as animal growth, calving, fertility and health. These findings suggest that GNAS domain-associated polymorphisms may serve as important genetic markers for future livestock breeding programs and support previous studies that candidate imprinted loci may act as molecular targets for the genetic improvement of agricultural populations. In addition, we present new evidence that the bovine NESP55 gene is epigenetically regulated as a maternally expressed imprinted gene in placental and intestinal tissues from 8-10 week old bovine foetuses.

Maternal Pelvic Size Not Predictive of Daughter's Breast Cancer or Ovarian Cancer in a Large Swedish Cohort

Recent studies from Finland reported that maternal pelvic size predicted daughters' breast and ovarian cancer, possibly because maternal pelvic size is a marker for in utero hormone exposure. We sought to replicate this association in 3,845 women born between 1915 and 1929 in Uppsala, Sweden, and followed from 1960 to 2002. Archived obstetric records provided the standard measures of maternal pelvic size (intercristal distance, interspinous distance, the intercristal-interspinous difference, and the external conjugate distance). The Swedish Cancer Registry ascertained cancer incidence, with 273 cohort members developing primary breast cancer, and 52 developing primary ovarian cancer during the follow-up period. There was no evidence (P > 0.1) of an association between any measure of maternal pelvic size and incidence of either breast or ovarian cancer. This was true both before and after adjustment for various characteristics of the women and their mothers, and in analyses stratified by age at diagnosis (<50 versus >or=50 years of age, as a proxy for premenopausal and postmenopausal ages). There was also no evidence of an association in subgroup analyses restricted specifically to those groups in which the Finnish data found the greatest effect. Our study is of comparable size to the Finnish studies and was highly powered (>99%) to detect effects of the magnitude they reported. Our nonreplication therefore casts doubt on the link between maternal pelvic size and risk of breast and ovarian cancer in the offspring.

A principal components approach to parent-to-newborn body composition associations in South India.

BackgroundSize at birth is influenced by environmental factors, like maternal nutrition and parity, and by genes. Birth weight is a composite measure, encompassing bone, fat and lean mass. These may have different determinants. The main purpose of this paper was to use anthropometry and principal components analysis (PCA) to describe maternal and newborn body composition, and associations between them, in an Indian population. We also compared maternal and paternal measurements (body mass index (BMI) and height) as predictors of newborn body composition.MethodsWeight, height, head and mid-arm circumferences, skinfold thicknesses and external pelvic diameters were measured at 30 ± 2 weeks gestation in 571 pregnant women attending the antenatal clinic of the Holdsworth Memorial Hospital, Mysore, India. Paternal height and weight were also measured. At birth, detailed neonatal anthropometry was performed. Unrotated and varimax rotated PCA was applied to the maternal and neonatal measurements.ResultsRotated PCA reduced maternal measurements to 4 independent components (fat, pelvis, height and muscle) and neonatal measurements to 3 components (trunk+head, fat, and leg length). An SD increase in maternal fat was associated with a 0.16 SD increase (β) in neonatal fat (p < 0.001, adjusted for gestation, maternal parity, newborn sex and socio-economic status). Maternal pelvis, height and (for male babies) muscle predicted neonatal trunk+head (β = 0. 09 SD; p = 0.017, β = 0.12 SD; p = 0.006 and β = 0.27 SD; p < 0.001). In the mother-baby and father-baby comparison, maternal BMI predicted neonatal fat (β = 0.20 SD; p < 0.001) and neonatal trunk+head (β = 0.15 SD; p = 0.001). Both maternal (β = 0.12 SD; p = 0.002) and paternal height (β = 0.09 SD; p = 0.030) predicted neonatal trunk+head but the associations became weak and statistically non-significant in multivariate analysis. Only paternal height predicted neonatal leg length (β = 0.15 SD; p = 0.003).ConclusionPrincipal components analysis is a useful method to describe neonatal body composition and its determinants. Newborn adiposity is related to maternal nutritional status and parity, while newborn length is genetically determined. Further research is needed to understand mechanisms linking maternal pelvic size to fetal growth and the determinants and implications of the components (trunk v leg length) of fetal skeletal growth.

The Impact of the Active Management of Risk in Pregnancy at Term on Birth Outcomes: A Randomized Clinical Trial

Although cesarean delivery rates continue to increase, little improvement has resulted in the overall quality of birth outcomes. An alternative approach, active management of risk in pregnancy at term (AMOR-IPAT), uses risk-based preventive induction of labor to make sure that women begin labor at a gestational age that maximizes the chance for vaginal delivery. This approach has, in retrospective studies, been associated with low cesarean delivery rates and improved birth outcomes. Both risk factors that interfere with placental growth or accelerate placental aging and those that promote fetal growth or limit maternal pelvic size are taken into account when estimating the upper limit of the optimal time of delivery (UL-OTD). With active management of risk, labor is planned to begin on or 1 to 4 days before the UL-OTD. Participating in the study were 136 women exposed to AMOR-IPAT and 134 were given usual care. The two groups were well matched for demographics, prenatal variables, and study risk factors. Labor was induced in 58% of exposed women and in 21.6% of the usual-care group. Cesarean delivery rates were similar, 10.3% in the exposed group, and 14.9% in the nonexposed group, and this finding largely persisted after adjusting for parity and short stature. Admission to neonatal intensive care was less frequent for the exposed group (1.5% versus 6.7%). The rate of uncomplicated vaginal birth was higher in the exposed group (73.5% versus 62.8%), and this group had a lower mean Adverse Outcome Index score. There were no significant group differences in rates of low 5-minute Apgar scores or major perineal injuries. High estimated blood loss was more frequent in women given usual care. Infants in the exposed group more often weighed <2500 g at birth, but none of them required neonatal intensive care for this reason. Larger randomized trials in more diverse populations are needed, but the present findings do challenge the belief that inducing labor necessarily leads to adverse birth outcomes.

Prevalence and risk factors for dystocia in dairy cattle: A review

This review focuses on the case definition of dystocia, its current prevalence and recent temporal trends, the different types of dystocia and their associated risk factors in dairy cattle. The reported dystocia rates in dairy cattle internationally are generally <5%, apart from those in the United States, where they are higher. Given the skewed distribution of herd dystocia rates, average figures mask high prevalence herds. Phenotypic dystocia trends are generally increasing internationally and this trend has been partially attributed to the introduction of Holstein genes. The principal types of dystocia differ between primiparae and pluriparae, with feto-pelvic disproportion (FPD) predominating in the former and fetal malposition in the latter. In order of importance, the two major determinants of FPD are calf birthweight and maternal pelvic size. Abnormal fetal position is most influenced by the number of fetuses, parity and calf sire breed. Adequate weighting of dystocia in selection indices, achievement of heifer rearing targets prior to both service and calving, and appropriate periparturient management decisions are prerequisites for controlling dystocia in dairy cattle.

Do big females have big pelves?

Previous studies have shown that maternal stature is a correlate of both pelvic size and reproductive efficiency. This study addresses the issue of body size and obstetric advantage. The relationship between pelvic size and three nonpelvic measures of body size is determined for females and males. The skeletal sample consists of blacks, whites, and Native Americans. The variables include 28 measures of the pelvis, length and head diameter of the femur, and clavicular length. The coefficient of multiple determination (CMD) is computed for each pelvic measure using multiple regression, with the three nonpelvic measures serving as the independent variables. Partial correlation coefficients are also calculated between each pelvic and nonpelvic variable, while controlling for the other two nonpelvic variables. The results show that all CMDs in females and all but one CMD in males are “low,” i.e., below 33%. The sexes are nonsignificantly different in their CMDs for 22 of the 28 pelvic variables; of the six variables that are significantly different, five are of the midplane. The sexes are also broadly comparable in their partial correlations. The results are explained as follows. First, the concordance between the sexes in the relationship between pelvic size and nonpelvic measures of body size is due to their genetic similarity for homologous structures. Second, as pelvic size is at the minimum at the midplane, the sexual differences in CMDs are the result of selection with respect to obstetrics. Third, four explanations for the low CMDs are discussed: 1) lack of populationally or racially specific analysis; 2) nonlinear relationship between pelvic size and nonpelvic measures of body size; 3) combination of negative allometric selection between newborn body weight and maternal stature and weight with positive selection for maternal pelvic size; and 4) hormonally induced increase in pelvic capacity during parturition. Am J Phys Anthropol 112:377–393, 2000. © 2000 Wiley-Liss, Inc.

Maternal pelvic size, measured by dual energy X-ray absorptiometry, predicts infant birthweight.

Indicators of infant birthweight are important because infant birthweight is related to later health outcomes. This study developed and validated new measures of the pelvis from dual energy absorptiometry (DEXA). Predictors of the new measures of maternal pelvic size were examined and the pelvic size measures were examined as predictors of infant birthweight. Data were drawn from a sample of 326 women in Hawaii and their 608 infants. The women were 45-60 years old at the time of the DEXA bone scan and when they recalled the birthweights of their infants. The birthweights were validated with birth certificate data. The women were participants in the Early Postmenopausal Interventional Cohort (EPIC) to study the effects of alendronate on bone density. Questions on birth histories were added to that study. Adolescent milk consumption and age at menarche were positively associated with the DEXA hip measure, while Asian ethnicity was negatively associated with the hip measure in multiple regression analysis. In multiple regression analysis, the hip measure, together with infant gender and gestational age predicted infant birthweight; mother's height, weight, and ethnicity did not add significantly to the model. DEXA provided measures of the pelvis, which varied by ethnicity, hormonal and nutritional variables, and which were indicators of infant birthweight. Am. J. Hum. Biol. 12:552-557, 2000. Copyright 2000 Wiley-Liss, Inc.

Do big females have big pelves?

Previous studies have shown that maternal stature is a correlate of both pelvic size and reproductive efficiency. This study addresses the issue of body size and obstetric advantage. The relationship between pelvic size and three nonpelvic measures of body size is determined for females and males. The skeletal sample consists of blacks, whites, and Native Americans. The variables include 28 measures of the pelvis, length and head diameter of the femur, and clavicular length. The coefficient of multiple determination (CMD) is computed for each pelvic measure using multiple regression, with the three nonpelvic measures serving as the independent variables. Partial correlation coefficients are also calculated between each pelvic and nonpelvic variable, while controlling for the other two nonpelvic variables. The results show that all CMDs in females and all but one CMD in males are "low," i.e., below 33%. The sexes are nonsignificantly different in their CMDs for 22 of the 28 pelvic variables; of the six variables that are significantly different, five are of the midplane. The sexes are also broadly comparable in their partial correlations. The results are explained as follows. First, the concordance between the sexes in the relationship between pelvic size and nonpelvic measures of body size is due to their genetic similarity for homologous structures. Second, as pelvic size is at the minimum at the midplane, the sexual differences in CMDs are the result of selection with respect to obstetrics. Third, four explanations for the low CMDs are discussed: 1) lack of populationally or racially specific analysis; 2) nonlinear relationship between pelvic size and nonpelvic measures of body size; 3) combination of negative allometric selection between newborn body weight and maternal stature and weight with positive selection for maternal pelvic size; and 4) hormonally induced increase in pelvic capacity during parturition.

Is the 20th century increase in human height entirely nongenetic?

The twentieth-century increase in human height in affluent nations may not be entirely due only to such nurturant considerations as food supply and electric lights. A possible genetic role might be found in interactions of food supply, maternal pelvic size, and height-survival/vulnerability links, and in mate selection. Humans seem to be following the paleontological principle that most species tend to evolve larger sizes over time.