Assessment of the variability in the dimensions of the intact pelvic canal in South Africans: A pilot study

Changes in plasticity of the pelvic girdle from infancy to late adulthood in Homo sapiens

Previous research on the effects of body mass on the pelvic girdle focused mostly on adult females and males. Because the ontogenetic plasticity level in the pelvis remains largely unknown, this study investigated how the association between body mass index (BMI) and pelvic shape changes during development. It also assessed how the large variation in pelvic shape could be explained by the number of live births in females. Data included CT scans of 308 humans from infancy to late adulthood with known age, sex, body mass, body stature, and the number of live births (for adult females). 3D reconstruction and geometric morphometrics was used to analyze pelvic shape. Multivariate regression showed a significant association between BMI and pelvic shape in young females and old males. The association between the number of live births and pelvic shape in females was not significant. Less plasticity in pelvic shape in adult females than during puberty, perhaps reflects adaptation to support the abdominopelvic organs and the fetus during pregnancy. Non-significant susceptibility to BMI in young males may reflect bone maturation accelerated by excessive body mass. Hormonal secretion and biomechanical loading associated with pregnancy may not have a long-term effect on the pelvic morphology of females.

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.

First assessed cervical dilatation: is it associated with oxytocin augmentation during labour? A retrospective cohort study in a university hospital in Switzerland

OBJECTIVES

The primary objective of this study was to examine the association between the first assessed cervical dilatation in a labourward and the use of oxytocin augmentation during labour. Further analysis was performed by examining the actual stage of labour at the point oxytocin was first administered to those women.

DESIGN

Retrospective cohort study with the data collected from the medical records of the hospital.

SETTING

University Hospital Bern, Switzerland PARTICIPANTS: 1933 term nulliparous and multiparous women with a singleton pregnancy giving birth during the period June 2013 and May 2017, representing Robson groups 1 and 3.

MEASUREMENTS AND FINDINGS

Descriptive statistics and multivariable logistic regression models were performed. It was found that for the entire process of labour, nulliparous and multiparous women (n = 1933) with a first cervical dilatation of 5 or more cm were less likely to be augmented with oxytocin (OR 0.64, 95% CI 0.46; 0.88 and OR 0.56, 95% CI 0.38; 0.82, respectively) compared to women with a first cervical dilatation of less than 5 cm. Out of these augmented women (n = 746) having a first cervical dilatation of 5 or more cm, they had a lower likelihood of being augmented during the first stage of labour compared to women with a first cervical dilatation of less than 5 cm (OR 0.45, 95% CI 0.29; 0.7 for nulliparae and OR 0.32, 95% CI 0.16; 0.6 for multiparae). Additionally, it was observed that other factors contributed to the application of oxytocin. One such example was that epidural analgesia was associated with a high risk of oxytocin augmentation in nulliparae (OR 13.88, 95% CI 9.29; 20.74) and multiparae (OR 15.52, 95% CI 9.94; 24.22). The application of oxytocin was also found to affect the caesarean section rate in nulliparous and multiparous women as it was 20% and 13% respectively for those with oxytocin versus 13% and 4% respectively for those without oxytocin.

KEY CONCLUSIONS

Early admission to the labourward is associated with an increased use of oxytocin to augment labour, particularly, during the first stage of labour. Epidural analgesia is a main predictor for oxytocin augmentation in nulliparous and multiparous women.

IMPLICATIONS FOR PRACTICE

Pregnant women warrant more appropriate support during early labour, avoiding early maternal exhaustion and excessive obstetrical interventions.