Correction for Stansfield et al., Biomechanical trade-offs in the pelvic floor constrain the evolution of the human birth canal

Compared with most other primates, humans are characterized by a tight fit between the maternal birth canal and the fetal head, leading to a relatively high risk of neonatal and maternal mortality and morbidities. Obstetric selection is thought to favor a spacious birth canal, whereas the source for opposing selection is frequently assumed to relate to bipedal locomotion. Another, yet underinvestigated, hypothesis is that a more expansive birth canal suspends the soft tissue of the pelvic floor across a larger area, which is disadvantageous for continence and support of the weight of the inner organs and fetus. To test this “pelvic floor hypothesis,” we generated a finite element model of the human female pelvic floor and varied its radial size and thickness while keeping all else constant. This allowed us to study the effect of pelvic geometry on pelvic floor deflection (i.e., the amount of bending from the original position) and tissue stresses and stretches. Deflection grew disproportionately fast with increasing radial size, and stresses and stretches also increased. By contrast, an increase in thickness increased pelvic floor stiffness (i.e., the resistance to deformation), which reduced deflection but was unable to fully compensate for the effect of increasing radial size. Moreover, larger thicknesses increase the intra-abdominal pressure necessary for childbirth. Our results support the pelvic floor hypothesis and evince functional trade-offs affecting not only the size of the birth canal but also the thickness and stiffness of the pelvic floor.

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HUBUNGAN PARITAS DENGAN DERAJAT LASERASI JALAN LAHIR DI POLINDES JETIS LOR KECAMATAN NAWANGAN KABUPATEN PACITAN

Jurnal Delima Harapan ◽

10.31935/delima.v6i1.73 ◽

2019 ◽

Vol 6 (1) ◽

pp. 48-53

Author(s):

Etika Desi Yogi

Keyword(s):

Correlation Analysis ◽

Pelvic Floor ◽

Vaginal Wall ◽

Labor Process ◽

Birth Process ◽

Birth Canal ◽

Calculation Results ◽

Independent Variable ◽

Relationship Of ◽

The Relationship

For women, the perineum is very important stretching and lubricating the perineum during labor can weaken the pelvic floor muscles in the vaginal wall, trauma to the perineum also causes discomfort and pain during sexual intercourse and an estimated 85% of maternal mothers experience birth canal lacerations (Kettle and Tohil 2008). One of the fears that are often felt by pregnant women, especially third timers, is fear of being torn and afraid of sewing. Especially for mothers who have experienced it, this can make their own trauma when facing the birth process later (USU, 2006). The purpose of this study was to determine the relationship of parity to the degree of laceration of the birth pathway in Jetis Lor Polindes, Nawangan District, Pacitan Regency. The design or design in this study is correlation analysis, with the "retrospective" approach. This study analyzed the relationship of parity with the degree of laceration of the birth path in Jetis Lor Polindes, Nawangan District, Pacitan Regency. In this study, the population was all mothers giving birth at Jetis Lor Polindes, Nawangan District, Pacitan Regency. The samples in this study were all mothers giving birth at Jetis Lor Polindes, Nawangan District, Pacitan Regency. In this study by looking at the last 1 year data. In this study the independent variable is parity. In this study the dependent variable is the degree of laceration of the birth canal. Based on the calculation results of SPSS 11.5 for Windows, it was found that there was no relationship between parity and laceration degrees in the Jetis Lor Polindes, Nawangan Subdistrict, Pacitan Regency, from the results of probability (sig. 2-tailed) 0.22 <0.05.The researcher hopes that the mother will seek information and increase knowledge about the labor process, so that with good knowledge will reduce lacerations on the birth canal

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The evolution of pelvic canal shape and rotational birth in humans

BMC Biology ◽

10.1186/s12915-021-01150-w ◽

2021 ◽

Vol 19 (1) ◽

Author(s):

Ekaterina Stansfield ◽

Barbara Fischer ◽

Nicole D. S. Grunstra ◽

Maria Villa Pouca ◽

Philipp Mitteroecker

Keyword(s):

Pelvic Floor ◽

Complex Shape ◽

Upright Posture ◽

Birth Canal ◽

Abdominal Organs ◽

Pelvic Inlet ◽

Deformation Stress ◽

The Stability ◽

Floor Stability ◽

Oval Shape

Abstract Background The human foetus typically needs to rotate when passing through the tight birth canal because of the complex shape of the pelvis. In most women, the upper part, or inlet, of the birth canal has a round or mediolaterally oval shape, which is considered ideal for parturition, but it is unknown why the lower part of the birth canal has a pronounced anteroposteriorly oval shape. Results Here, we show that the shape of the lower birth canal affects the ability of the pelvic floor to resist the pressure exerted by the abdominal organs and the foetus. Based on a series of finite element analyses, we found that the highest deformation, stress, and strain occur in pelvic floors with a circular or mediolaterally oval shape, whereas an anteroposterior elongation increases pelvic floor stability. Conclusions This suggests that the anteroposterior oval outlet shape is an evolutionary adaptation for pelvic floor support. For the pelvic inlet, by contrast, it has long been assumed that the mediolateral dimension is constrained by the efficiency of upright locomotion. But we argue that the mediolateral elongation has evolved because of the limits on the anteroposterior diameter imposed by upright posture. We show that an anteroposteriorly deeper inlet would require greater pelvic tilt and lumbar lordosis, which compromises spine health and the stability of upright posture. These different requirements of the pelvic inlet and outlet likely have led to the complex shape of the pelvic canal and to the evolution of rotational birth characteristic of humans.

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Shaping birth: variation in the birth canal and the importance of inclusive obstetric care

Philosophical Transactions of the Royal Society B Biological Sciences ◽

10.1098/rstb.2020.0024 ◽

2021 ◽

Vol 376 (1827) ◽

Author(s):

Lia Betti

Keyword(s):

White Women ◽

Obstetric Care ◽

European Ancestry ◽

Human Populations ◽

Maternal Child Health ◽

Birth Canal ◽

Pelvic Morphology ◽

Pelvic Shape ◽

Training Need ◽

Human Birth

Regional variation in pelvic morphology and childbirth has long occurred alongside traditional labour support and an understanding of possible normal courses of childbirth for each population. The process of migration and globalization has broken down these links, while a European model of ‘normal’ labour has become widespread. The description of ‘normal’ childbirth provided within obstetrics and midwifery textbooks, in fact, is modelled on a specific pelvic morphology that is common in European women. There is mounting evidence, however, that this model is not representative of women's diversity, especially for women of non-white ethnicities. The human birth canal is very variable in shape, both within and among human populations, and differences in pelvic shapes have been associated with differences in the mechanism of labour. Normalizing a white-centred model of female anatomy and of childbirth can disadvantage women of non-European ancestry. Because they are less likely to fit within this model, pelvic shape and labour pattern in non-white women are more likely to be considered ‘abnormal’, potentially leading to increased rates of labour intervention. To ensure that maternal care is inclusive and as safe as possible for all women, obstetric and midwifery training need to incorporate women's diversity. This article is part of the theme issue ‘Multidisciplinary perspectives on social support and maternal–child health’.

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Human variation in the shape of the birth canal is significant and geographically structured

Proceedings of The Royal Society B Biological Sciences ◽

10.1098/rspb.2018.1807 ◽

2018 ◽

Vol 285 (1889) ◽

pp. 20181807 ◽

Cited By ~ 17

Author(s):

Lia Betti ◽

Andrea Manica

Keyword(s):

Morphological Diversity ◽

Neutral Evolution ◽

Human Populations ◽

Shape Variation ◽

Birth Canal ◽

Neutral Genetic Diversity ◽

A Minor ◽

Human Birth ◽

European Women ◽

Oval Shape

The human birth canal shows a tight fit with the size of the neonate, which can lead to obstetric complications. This is not the case in other apes, and has been explained as the outcome of conflicting evolutionary pressures for bipedal locomotion and parturition of a highly encephalized fetus. Despite the suggested evolutionary constraints on the female pelvis, we show that women are, in fact, extremely variable in the shape of the bony birth canal, with human populations having differently shaped pelvic canals. Neutral evolution through genetic drift and differential migration are largely responsible for the observed pattern of morphological diversity, which correlates well with neutral genetic diversity. Climatic adaptation might have played a role, albeit a minor one, with populations from colder regions showing a more transversally oval shape of the canal inlet. The significant extent of canal shape variation among women from different regions of the world has important implications for modern obstetric practice in multi-ethnic societies, as modern medical understanding has been largely developed on studies of European women.

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The evolution of pelvic canal shape and rotational birth in humans

10.21203/rs.3.rs-495939/v1 ◽

2021 ◽

Author(s):

Ekaterina Stansfield ◽

Barbara Fischer ◽

Philipp Mitteroecker

Keyword(s):

Pelvic Floor ◽

Complex Shape ◽

Birth Canal ◽

Abdominal Organs ◽

Pelvic Inlet ◽

Deformation Stress ◽

The Stability ◽

Floor Stability ◽

Pelvic Floor Support ◽

Oval Shape

Abstract The human foetus needs to rotate when passing through the tight birth canal because of the complex shape of the pelvis. In most women the upper part, or inlet, of the birth canal has a round or mediolaterally oval shape, which is considered ideal for parturition, but it is unknown why the lower part, or outlet, of the birth canal has a pronounced anteroposteriorly oval shape. Here we show that the shape of the lower birth canal affects the ability of the pelvic floor to resist pressure exerted by the abdominal organs and the foetus. Based on a series of finite element analyses, we found that the highest deformation, stress and strain occur in pelvic floors with a circular or mediolaterally oval shape, whereas an anteroposterior elongation increases pelvic floor stability. This suggests that the anteroposterior oval outlet shape is an evolutionary adaptation for pelvic floor support. For the pelvic inlet, by contrast, it has long been assumed that the mediolateral dimension is constrained by the efficiency of upright locomotion. But we argue that upright stance limits the anteroposterior dimension of the inlet. A deeper inlet requires greater pelvic tilt and lumbar lordosis, which compromises spine health and the stability of upright posture. These different requirements on the pelvic inlet and outlet have led to the complex shape of the human pelvic canal and to the evolution of rotational birth.

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Mechanism of birth in chimpanzees: humans are not unique among primates

Biology Letters ◽

10.1098/rsbl.2011.0214 ◽

2011 ◽

Vol 7 (5) ◽

pp. 686-688 ◽

Cited By ~ 25

Author(s):

Satoshi Hirata ◽

Koki Fuwa ◽

Keiko Sugama ◽

Kiyo Kusunoki ◽

Hideko Takeshita

Keyword(s):

Pan Troglodytes ◽

Comparative Studies ◽

Head Rotation ◽

Birth Canal ◽

Video Recordings ◽

Evolutionary Scenario ◽

Human Newborn ◽

In Captivity ◽

Human Uniqueness ◽

Human Birth

Researchers have argued that the process of human birth is unique among primates and mammals in that the infant emerges with its face oriented in the opposite direction from its mother (occiput anterior) and head rotation occurs in the birth canal. However, this notion of human uniqueness has not been substantiated, because there are few comparative studies of birth in non-human primates. This paper reports the mechanism of birth in chimpanzees ( Pan troglodytes ) based on the first clear, close-up video recordings of three chimpanzee births in captivity. In all three cases, the foetus emerged with an occiput anterior orientation, and the head and body rotated after the head had emerged. Therefore, these characteristics are not uniquely human. Furthermore, in two of the three cases, the chimpanzee newborns landed on the ground without being guided from the birth canal by the mother. The fact that the human newborn emerges with an occiput anterior orientation has thus far been taken as evidence for the necessity of midwifery in modern humans, but this view also needs revision. Our observations raise the need to reconsider the evolutionary scenario of human birth.

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Novel players fine-tune plant trade-offs

Essays in Biochemistry ◽

10.1042/bse0580083 ◽

2015 ◽

Vol 58 ◽

pp. 83-100 ◽

Cited By ~ 25

Author(s):

Selena Gimenez-Ibanez ◽

Marta Boter ◽

Roberto Solano

Keyword(s):

Ubiquitin Ligase ◽

Feedback Loop ◽

Molecular Level ◽

26S Proteasome ◽

Signalling Molecules ◽

Transcriptional Reprogramming ◽

Trade Offs ◽

Jaz Proteins ◽

Regulatory Feedback Loop ◽

Fine Tune

Jasmonates (JAs) are essential signalling molecules that co-ordinate the plant response to biotic and abiotic challenges, as well as co-ordinating several developmental processes. Huge progress has been made over the last decade in understanding the components and mechanisms that govern JA perception and signalling. The bioactive form of the hormone, (+)-7-iso-jasmonyl-l-isoleucine (JA-Ile), is perceived by the COI1–JAZ co-receptor complex. JASMONATE ZIM DOMAIN (JAZ) proteins also act as direct repressors of transcriptional activators such as MYC2. In the emerging picture of JA-Ile perception and signalling, COI1 operates as an E3 ubiquitin ligase that upon binding of JA-Ile targets JAZ repressors for degradation by the 26S proteasome, thereby derepressing transcription factors such as MYC2, which in turn activate JA-Ile-dependent transcriptional reprogramming. It is noteworthy that MYCs and different spliced variants of the JAZ proteins are involved in a negative regulatory feedback loop, which suggests a model that rapidly turns the transcriptional JA-Ile responses on and off and thereby avoids a detrimental overactivation of the pathway. This chapter highlights the most recent advances in our understanding of JA-Ile signalling, focusing on the latest repertoire of new targets of JAZ proteins to control different sets of JA-Ile-mediated responses, novel mechanisms of negative regulation of JA-Ile signalling, and hormonal cross-talk at the molecular level that ultimately determines plant adaptability and survival.

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