Magnetic resonance-based serial pelvimetry: do maternal pelvic dimensions change during pregnancy?

Magnetic resonance imaging pelvimetric measurements as predictors for emergent cesarean delivery in obstructed labor

Objective

This study aimed to investigate the usefulness of various magnetic resonance imaging (MRI) pelvimetric parameters for predicting emergent cesarean delivery due to obstructed labor.

Study design

This was a prospective observational study. MRI pelvimetry was performed in cases of a clinically suspected maternal narrow pelvis, maternal short stature, fetal overgrowth, and abnormal placental position. MRI pelvimetry was performed at 34.7 ± 4.2 gestational weeks using a 1.5 T MRI system. The pelvic inlet angle, pelvic inclination, obstetric conjugate, sacral outlet diameter (SOD), and coccygeal pelvic outlet were measured in the sagittal section. The interspinous diameter and intertuberous diameter were measured in coronal sections. Fetal anomalies, cesarean deliveries before the onset of labor, and non-reassuring fetal status were excluded from the analysis.

Results

MRI pelvimetry was performed in 154 patients. After excluding 76 cases, including 19 cases of absolute cephalopelvic disproportion, 78 cases of trial of labor were included. Of these, 63 were vaginal deliveries and 15 were emergent cesarean deliveries due to obstructed labor. The cut-off value for body mass index (BMI) was 22.2, with an area under the curve (AUC) of 0.69, for predicting obstructed labor. The cut-off value for the SOD was 10.7 cm with an AUC of 0.69. BMI alone had a sensitivity of 80%, specificity of 66%, positive predictive value (PPV) of 36%, and negative predictive value (NPV) of 93%. When BMI and SOD were combined, sensitivity was 53%, specificity was 90%, PPV was 57%, and NPV was 89%. The odds ratio for emergent cesarean delivery was 5.42 (95% confidence interval 1.06-27.6, p = 0.041) if the SOD was less than the cut-off value in the binomial logistic regression analysis in cases with an BMI > 22.

Conclusion

We confirmed that MRI pelvimetry was a reliable tool for better patient selection for obstructed labor. The SOD was the best predictor of obstructed labor, with a cut-off value of 10.7 cm for women with a low BMI.

Predictive Value of MRI Pelvimetry in Vaginal Delivery and Its Practicability in Prolonged Labour-A Prospective Cohort Study

BACKGROUND

Pelvic dimensions are crucial variables in the labour process. We used magnetic resonance imaging (MRI) pelvimetry to predict the probability of vaginal delivery and distinguish the cephalopelvic disproportion risk in women with prolonged active labour.

METHODS

This prospective cohort study enrolled term nulliparous women willing to undergo MRI pelvimetry and a trial of labour. A nomogram, with vaginal birth as the outcome, was developed and evaluated by calibration curve and decision curve analyses. The pairwise association between maternal and fetal parameters and a prolonged first stage of labour was quantified.

RESULTS

Head circumference (HC), abdominal circumference (AC), intertuberous distance (ITD), interspinous diameter (ISD), and body mass index (BMI) were introduced to develop a nomogram with good diagnostic performance (area under the curve = 0.799, sensitivity = 83%, and specificity = 73%). The cephalopelvic index of diameter (CID) in 54 women with a prolonged first stage of labour was much smaller in those who delivered via cesarean section compared with those who delivered vaginally (18.09 ± 1.14 vs. 21.29 ± 1.06; p = 0.046).

CONCLUSIONS

An MRI pelvimetry-based nomogram may predict the probability of vaginal delivery. Practitioners should reassess the pelvimetry parameters to decide whether the trial of labour should be continued if it is prolonged.

The relation between head circumference and mid pelvic circumference: A simple index for cephalo-pelvic disproportion evaluation

INTRODUCTION

Cephalo-pelvic-disproportion (CPD) is one of the most common obstetric complications. Since CPD is the disproportion between the fetal head and maternal bony pelvis, evaluation of the head-circumference (HC) relative to maternal bony pelvis may be a useful adjunct to pre-labor CPD evaluation. The aim of the present study was a proof-of-concept evaluation of the ratio between HC to pelvic circumference (PC) as a predictor of CPD.

METHODS

Of 11,822 deliveries, 104 cases that underwent an abdomino-pelvic CT for any medical indication and who underwent normal vaginal deliveries (NVD) (n=84) or cesarean deliveries (CD) due to CPD (n=20) were included retrospectively. Maternal pelvis dimensions were reconstructed and neonatal HC, as a proxy for fetal HC, were measured. The correlation between cases of CPD and Cephalo-Pelvic Circumference Index (CPCI), which represents the ratio between the HC and PC in percent (HC/PC *100) was evaluated.

RESULTS

The mid-pelvis cephalo-pelvic circumference index (MP-CPCI) was larger in CD groups as compared to the NVD group: 103±11 vs. 97±8% respectively (p=0.0003). In logistic regression analysis, the MP-CPCI was found to be independently associated with CD due to CPD: each 1% increase in MP-CPCI increased the likelihood of CD for CPD by 11% (aOR 1.11, CI 95% 1.03-1.19, p=0.004). The adjusted odds ratio for CD due to CPD increased incrementally as the MP-CPCI increased, from 3.56 (95%CI, 1.01-12.6) at MP-CPCI of 100, to 5.6 (95%CI, 1.63-19.45) at 105, 21.44 (95%CI, 3.05-150.84) at 110, and 28.88 (95%CI, 2.3-362.27) at MP-CPCI of 115 Conclusions: The MP-CPCI, representing the relative dimensions of the fetal HC and maternal PC, is a simple tool that can potentially distinguish between parturients at lower and higher risk of CPD. Prospective randomized studies are required to evaluate the feasibility of prenatal pelvimetry and MP-CPCI to predict the risk of CPD during labor.

Pelvic capacity in pregnant women, identified using magnetic resonance imaging

INTRODUCTION

Maternal pelvic capacity plays a major role during childbirth because the passage of the fetus through the bony birth canal enables vaginal birth. Maternal birthing position may influence pelvic capacity because upright positions optimize capacity, possibly due to free movement of the pelvic joints. Herein, pelvic capacity was assessed by comparing changes in pelvic dimensions across pregnancy and in three birthing positions.

MATERIAL AND METHODS

This diagnostic imaging study of 50 pregnant women was conducted at Aarhus University Hospital, Denmark. Pelvic measurements were obtained with 1.5 T magnetic resonance pelvimetry during gestational weeks 20 and 32, in three birthing positions: kneeling squat, semi-lithotomy and supine. Pelvic capacity was compared between gestational weeks and positions.

RESULTS

In all three positions there is an overall increase in pelvic capacity from gestational week 20-32 at both the pelvic inlet and outlet. Comparing pelvic capacity at gestational week 32 between the semi-lithotomy and supine positions revealed that the pelvic inlet was larger in the supine position, whereas the mean pelvic outlet was 0.2 cm (p < 0.001) larger in the semi-lithotomy position. Likewise, the pelvic inlet was larger in the supine than in the kneeling squat position. Shifting from supine to kneeling squat position increased the midplane and pelvic outlet dimensions by up to 1 cm (p < 0.001).

CONCLUSIONS

The finding herein of an increased pelvic capacity as the pregnancy progresses is novel. Further, the results indicate that the supine position is optimal for increasing pelvic inlet size, whereas the semi-lithotomy and kneeling squat positions are optimal for increasing mid- and outlet-pelvic capacities.

Asymmetric pelvis and term breech presentation: is planned vaginal delivery still a safe option?

PURPOSE

To evaluate the obstetrical prognosis of term breech delivery in case of asymmetric pelvis.

METHODS

An observational, comparative, retrospective, bi-centric study of 559 patients who had a computer tomography pelvimetry prior to delivery of a term breech presentation was conducted between August 2013 and August 2019. Patients with an attempted vaginal delivery were divided into two groups: a group of asymmetric pelvis (AP) when the difference between the lengths of both oblique diameters was ≥ 1 cm and a group of symmetric pelvis (SP) when the two oblique diameters differed by < 1 cm. The primary outcome was the rate of vaginal delivery. Secondary outcomes were a composite variable of neonatal and maternal morbidity and mortality.

RESULTS

Of the 370 patients who attempted a vaginal breech delivery, 8% (n = 29) had an AP and 92% (n = 341) had a SP. In the AP group, the vaginal delivery rate was higher (93% versus 78%, p = 0.05). There was no statistically significant difference in neonatal (3% versus 1% in the AP and SP groups, respectively, p = 0.4) and maternal (17% versus 23% in the AP and SP groups, respectively, p = 0.5) morbidity and mortality.

CONCLUSION

When a pelvimetry is performed before an attempt of vaginal breech delivery, a difference of less than two centimetres between both oblique diameters does not seem to reduce the rate of vaginal birth and is not an indication for an elective caesarean section.

CT observation of L5 pedicle screw fixation shielding by the iliac wing width and height

OBJECTIVE

The height and width of the iliac wing were measured using three-dimensional computed tomography(3D-CT), and the extent to which the iliac wing occluded the entry point of the 5th lumbar vertebra pedicle screw(L5PS) was observed and graded according to severity. The overall goal was to study the influence of the height and width of the iliac wing on L5PS insertion.

PATIENTS AND METHODS

This study included 350 cases (179 males and 171 females) where the L1-S2 region was obtained. We reconstructed 3D-CT in our study for anatomic analysis. The width and height of the iliac wing were measured on CT axial and oblique sagittal images, respectively. The degree of the L5PS entry point was determined by the data of iliac wing width and height, and divided into 0, I, II and III levels. The association between width and height of the iliac wing among males and females was also analyzed in this paper.

RESULTS

The incidence of shielding of the L5PS entry point by the height and width of the ilium wing were 20.0 % and 19.4 %, respectively. The overall incidence of obstruction of L5PS by the width of the ilium wing was 27.3 % in males and 12.3 % in females. In total, there were 27, 14, and 8 male patients with level I, II, and III shielding, respectively. There were 12, 7, and 2 females with level I, II, and III shielding, respectively. The overall incidence with which the height of the ilium wing obstructed L5PS was 24.0 % in males and 14.6 % in females, of which there were 23 males with level Ⅰ shielding, 16 males with level Ⅱ shielding, 4 males with level Ⅲ shielding, 13 females with level Ⅰ shielding, 8 females with level Ⅱ shielding, and 4 females with level Ⅲ shielding.

CONCLUSIONS

The height of the ilium caused obstruction of the L5PS more frequently than the width of the ilium, and males had a higher incidence of iliac wing occlusion than females at both the height and width. The degree of L5PS entry point shielding by the iliac wing width along the horizontal axis was not completely consistent with that of L5PS shielding on the oblique sagittal plane.

The Association of Variations in Hip and Pelvic Geometry With Pregnancy-Related Sacroiliac Joint Pain Based on a Longitudinal Analysis

STUDY DESIGN

Cross-sectional study using radiological measurements and longitudinal data analysis.

OBJECTIVE

We aim to explore hip/pelvic geometry on anteroposterior radiographs and examine if such parameters are associated with clinical symptoms.

SUMMARY OF BACKGROUND DATA

Pregnancy-related sacroiliac joint pain is a common disease and is responsible to the disability of daily activities. The etiology is likely to be correlated with the biomechanical factors which are determined by trunk load and hip/pelvic geometry. Previous studies have already found the association between symptoms and weight increase during pregnancy. However, the relationship between bony anatomy and pregnancy-related sacroiliac joint pain remains unknown.

METHODS

In total, 72 women were included in the final analysis. In pregnant women with self-reported sacroiliac joint pain, pain scores at 12, 24, 30, and 36 weeks of pregnancy were recorded and included in a mixed-effect linear regression model as dependent variables. The radiological measurements were included as independent variables. Furthermore, to investigate the relationship between hip/pelvic geometry and the activity-specific nociceptive phenomenon, the radiological measurements between patients with and without activity-induced pain were compared using a binominal logistic regression model.

RESULTS

The relative bilateral is chial tuberosity distance (betta coefficient: 0.078; P = 0.015) and the relative bilateral femoral head length (betta coefficient: 0.011; P = 0.028) showed significant interactions with the slope of pain scores. Moreover, women whose pain exacerbate during prolonged walking had a higher odds in hip/pelvic geometry of the bilateral ischial tuberosity distance (odds ratio [OR]: 1.12; P = 0.050) and the bilateral femoral head length (OR: 1.16; P = 0.076) with approximately significant P-value.

CONCLUSION

These data indicate hip/pelvic anatomical variations are associated with the degree of pain increasing and the activity-specific pain during pregnancy, which may help to have further understanding on the biomechanical factor in developing pregnancy-related sacroiliac joint pain.

LEVEL OF EVIDENCE

3.

MRI-based pelvimetric measurements as predictors for a successful vaginal breech delivery in the Frankfurt Breech at term cohort (FRABAT)

OBJECTIVES

The purpose of this study was to investigate the role of the maternal pelvis, assessed by MRI pelvimetry in nulliparous women expecting a term fetus in breech presentation, to predict a successful and safe vaginal birth.

STUDY DESIGN

In this monocentric and anonymized cohort study, we enrolled 367 nulliparous women with breech presentation at 39⁺⁰ to 41⁺⁰ weeks of gestation during a period of 8 years at the University Women's Hospital in Frankfurt/Main. Pelvic measurements were obtained by standard MRI imaging. We correlated the obstetric conjugate, the pubic angle and the distance between the ischial tuberosities (intertuberous distance) with the maternal and fetal outcomes of vaginally intended breech births. The data was evaluated using logistic regression analysis.

RESULTS

241 of 367 participants (65.7%) experienced a successful vaginal delivery whereas 126 patients (34.3%) were subjected to secondary cesarean section. An increasing obstetric conjugate was significantly associated with an increasing rate of successful vaginal deliveries. No significant correlation of the intertuberous distance and the pubic angle with the mode of delivery could be shown. Although statistically not significant, we were able to define cut-off values of 10.9 cm in the intertuberous distance and 70° in the pubic angle; below these values, no successful vaginal delivery was recorded. No significant differences in the short-term outcomes were seen between the neonates of the vaginal delivery and the cesarean section groups. Inter- and intraobserver variability showed excellent reproducibility for all MRI parameters.

CONCLUSION

The obstetric conjugate correlates with the rate of vaginal deliveries in nulliparous women at term and can be used as a useful criterion for pre-selection and counseling of women with breech presentation and the desire for a vaginal delivery.

Three-dimensional/four-dimensional transperineal ultrasound: clinical utility and future prospects

During the last decade, there has been a huge advancement in the use of transperineal ultrasound (TPU) in the field of obstetrics and gynecology. Its main applications in obstetrics include the monitoring of fetal progression in labor and recently the assessment of maternal pelvic dimensions, whereas in gynecology, TPU is at present widely used for the evaluation of the female pelvic floor, opening new boundaries for the assessment of pelvic floor disorders. The association of volumetric three-dimensional techniques has largely contributed to the remarkable progress that has occurred in the use of TPU. The aim of this paper is to offer an overview of the advantages, challenges and future perspectives of the use of TPU for women’s imaging.

New MRI Criteria for Successful Vaginal Breech Delivery in Primiparae

Background

Even if lower vaginal delivery success rates and impaired neonatal short-term outcomes have been reported for primiparous women with breech presentation, vaginal breech delivery remains an option for carefully selected patients. Because Magnetic resonance imaging (MRI) pelvimetry can provide additional information on maternal pelvic morphology, we sought to identify new MRI parameters that predict successful vaginal breech delivery.

Methods

In this retrospective unicentre study, 240 primiparous women with breech presentation at term underwent MRI pelvimetry. For all patients vaginal delivery was planned, according to German guidelines and if the conjugata vera (CV) was ≥12 cm. The patients with uneventful vaginal deliveries and the patients who underwent a secondary caesarean section were compared according to pelvimetric parameters and outcomes. Regression analyses were performed.

Results

In the vaginal delivery group (n = 162, (67.5%)), the distance between the spinae ischiadicae (interspinous diameter, ISD) was significantly enlarged. The ISD significantly influenced the mode of delivery in the regression analyses. The CV did not significantly differ between the groups. The patients with successful vaginal deliveries were significantly younger than the patients who underwent caesarean section. In the receiver operating characteristic (ROC) analysis, the area under the curve (AUC) for ISD was 67.7% (p<0.001, 95% CI [0.303–0.642]) and was higher considering the mother’s age (AUC = 73.1%, p<0.001, 95% CI [0.662–0.800]). The neonatal short-term outcomes were comparable in both groups.

Conclusion

The additional use of ISD may predict successful vaginal breech delivery and may be superior to the CV, which is more commonly used.

Trial Registration

DRKS00009957

Pelvimetry by Three-Dimensional Computed Tomography in Non-Pregnant Multiparous Women Who Delivered Vaginally

Background

We assessed retrospectively the reference values of pelvic dimensions by 3D CT performed for non-obstetrical indications in non-pregnant multiparous women with a successful vaginal delivery. We further aimed to evaluate the impact of maternal short stature on these parameters.

Material/Methods

The 3D CT pelvimetry was performed retrospectively in 203 non-pregnant women selected consecutively if they had at least one singleton term delivery with head presentation and if there was no history of maternal or fetal birth trauma or cerebral palsy after childbirth. With standard sagittal and reformatted axial-oblique views, anteroposterior including three conjugates of pelvic inlet, transverse, posterior sagittal diameters of pelvic inlet, the plane of greatest diameter, the plane of least diameter, and pelvic outlet were measured. Selected obstetric parameters were collected.

Results

Overall, the pelvises had transverse oval appearance in inlet and size of the female pelvis. The diagonal conjugate was at least 15 mm longer than the obstetric conjugate. Women with short stature had lower maximal birth weight, and this was in accordance with their somewhat lower pelvic diameters.

Conclusions

The findings of this study present the reference values of the main planes of the true pelvis by 3D CT pelvimetry in a relatively large group of multiparous women who passed a trial of labor successfully. Overall, the pelvises had features of female pelvic bony structure although pelvic diameters were somewhat lower in multiparous women with short stature. The 3D pelvimetry with CT applications may be used as an adjunct to clinical and ultrasonographic examinations to rule out cephalopelvic dystocia in selected cases.

Using survival analysis to determine association between maternal pelvis height and antenatal fetal head descent in Ugandan mothers

Introduction

Fetal head descent is used to demonstrate the maternal pelvis capacity to accommodate the fetal head. This is especially important in low resource settings that have high rates of childbirth related maternal deaths and morbidity. This study looked at maternal height and an additional measure, maternal pelvis height, from automotive engineering. The objective of the study was to determine the associations between maternal: height and pelvis height with the rate of fetal head descent in expectant Ugandan mothers.

Methods

This was a cross sectional study on 1265 singleton mothers attending antenatal clinics at five hospitals in various parts of Uganda. In addition to the routine antenatal examination, each mother had their pelvis height recorded following informed consent. Survival analysis was done using STATA 12.

Results

It was found that 27% of mothers had fetal head descent with an incident rate of 0.028 per week after the 25th week of pregnancy. Significant associations were observed between the rate of fetal head descent with: maternal height (Adj Haz ratio 0.93 P < 0.01) and maternal pelvis height (Adj Haz ratio 1.15 P < 0.01).

Conclusion

The significant associations observed between maternal: height and pelvis height with rate of fetal head descent, demonstrate a need for further study of maternal pelvis height as an additional decision support tool for screening mothers in low resource settings.

Does pregnancy and/or shifting positions create more room in a woman's pelvis?

OBJECTIVE

The purpose of this study was to assess the impact of different positions on pelvic diameters by comparing pregnant and nonpregnant women who assumed a dorsal supine and kneeling squat position.

STUDY DESIGN

In this cohort study from a tertiary referral center in Germany, we enrolled 50 pregnant women and 50 nonpregnant women. Pelvic measurements were obtained with obstetric magnetic resonance imaging pelvimetry with the use of a 1.5-T scanner. We compared measurements of the depth (anteroposterior (AP) and width (transverse diameters) of the pelvis between the 2 positions.

RESULTS

The most striking finding was a significant 0.9-1.9 cm increase (7-15%) in the average transverse diameters in the kneeling squat position in both pregnant and nonpregnant groups. The average bispinous diameter in the pregnant group increased from 12.6 cm ± 0.65 cm in the supine dorsal to 14.5 cm ± 0.64 cm (P < .0001) in the kneeling squat; in the nonpregnant group the increase was from 12 cm ± 0.76 cm to 13.9 cm ± 1.04 cm (P < .0001). The average bituberous diameter in the pregnant group increased from 13.6 cm ± 0.93 cm in the supine dorsal to 14.5 cm ± 0.83 cm (P < .0001) in the kneeling squat position; in the nonpregnant women the increase was from 12.6 cm ± 0.92 cm to 13.5 cm ± 0.88 cm (P < .0001).

CONCLUSION

A kneeling squat position significantly increases the bony transverse and anteroposterior dimension in the mid pelvic plane and the pelvic outlet. Because this indicates that pelvic diameters change when women change positions, the potential for facilitation of delivery of the fetal head suggests further research that will compare maternal delivery positions is warranted.

Association between obstetric conjugate diameter measured by transabdominal ultrasonography during pregnancy and the type of delivery

Background

Normal morphological features of the maternal pelvis are an important prerequisite to vaginal delivery.

Objectives

We aimed to evaluate the association between obstetric conjugate diameter (OCD) measured by ultrasonography and the type of delivery, vaginally (V) or by cesarean (C) section.

Patients and Methods

Pelvimetry was performed in 200 primigravid women for fetal cephalic presentation. The OCD was measured twice by transabdominal ultrasonography during 25-30 weeks and 30-35 weeks of pregnancy.

Results

The mean OCD of both sonographies in groups V and C was 125.51± 8.35 mm (105-144.5) and 112.99 ± 8.53 mm (96-134.5), respectively, which was significantly lower in group C (P<0.001). The values of OCD between the first and second measurements were not different significantly (P=0.065). C-section was indicated in 65 (32.5%) mothers. The optimal cut-off point for the OCD in the prediction of vaginal delivery was ≥ 119.75 mm, with a sensitivity and specificity of 80% and 78.5%, respectively.

Conclusion

The US measurement of OCD might be an accurate method that almost always remains constant during late pregnancy; it is easy to measure and might be confidentially employed for predicting C-section, but needs more precise studies to be used widely.

Human birth observed in real-time open magnetic resonance imaging

OBJECTIVE

Knowledge about the mechanism of labor is based on assumptions and radiographic studies performed decades ago. The goal of this study was to describe the relationship between the fetus and the pelvis as the fetus travels through the birth canal, using an open magnetic resonance imaging (MRI) scanner.

STUDY DESIGN

The design of the study used a real-time MRI series during delivery of the fetal head.

RESULTS

Delivery occurred by progressive head extension. However, extension was a very late movement that was observed when the occiput was in close contact with the inferior margin of the symphysis pubis, occurring simultaneously with gliding downward of the fetal head.

CONCLUSION

This observational study shows, for the first time, that birth can be analyzed with real-time MRI. MRI technology allows assessment of maternal and fetal anatomy during labor and delivery.