Role of fetal head-circumference-to-maternal-height ratio in predicting Cesarean section for labor dystocia: prospective multicenter study

Neonatal head circumference to maternal mid-transverse pelvic distance ratio as a key anatomical predictor for dystocia: Retrospective case-control study

OBJECTIVE

This study aimed to examine maternal and neonatal factors in cesarean deliveries due to dystocia, including cephalopelvic disproportion, latent-phase prolongation, and fetal malposition or malpresentation. Additionally, we sought to compare the differences between the dystocia subgroups.

METHOD AND MATERIALS

This retrospective case-control study included women who delivered between January 2010 and June 2021 after 37 weeks of pregnancy and underwent abdominal-pelvic CT scans within 5 years before and after delivery. Neonatal factors were extracted from medical charts immediately after delivery.

RESULTS

Among the 292 women studied, those with cesarean deliveries for dystocia were older (mean ± SD, 34.2 ± 4.27 vs. 32.2 ± 3.8, p-value = 0.002), had higher pre-pregnancy BMI (22.7 ± 3.67 vs. 21.4 ± 3.48, p-value = 0.012) and term-BMI (27.4 ± 3.72 vs. 25.9 ± 3.66, p-value = 0.010), shorter interspinous distance (ISD, the distance between ischial spine) (10.8 ± 0.76 vs. 11.2 ± 0.85 cm, p-value = 0.003), and longer head circumference (HC) (35 ± 1.47 vs. 34.4 ± 1.36 cm, p-value = 0.003) compared to those who had vaginal deliveries. Univariate logistic regression for dystocia revealed associations between HC/maternal height and HC/ISD ratios (OR, 2.02 [95% confidence interval, CI, 1.4 ~ 2.92], 12.13 [3.2 ~ 46.04], respectively). Multivariate logistic analysis indicated that maternal age, ISD, and HC were significant factors for dystocia (OR, 1.11 [95% CI, 1.01 ~ 1.21], 0.49 [0.26 ~ 0.91], 1.53 [1.07 ~ 2.19], respectively). The subgroup with latent-phase prolongation exhibited the lowest birthweight/term-BMI ratio (124 ± 18.8 vs. 113 ± 10.3 vs. 134 ± 19.1, p-value = 0.013).

CONCLUSION

The HC/ISD ratio emerged as a crucial predictor of dystocia, suggesting that reducing term-BMI could potentially mitigate latent-phase prolongation. Further research assessing the maternal mid-pelvis during pregnancy and labor is warranted, along with efforts to reduce BMI during pregnancy.

Prediction of persistent occiput posterior position by sonographic assessment of fetal head attitude at start of second stage of labor: prospective study

OBJECTIVES

To evaluate the relationship between the attitude of the fetal head quantified by means of the chin-to-chest angle (CCA) in fetuses in occiput posterior (OP) position at the beginning of the second stage of labor, and persistent OP position at birth.

METHODS

This was a single-center, prospective observational study conducted at the University Hospital of Parma, Parma, Italy. We included singleton pregnancies at term with fetuses in the OP position at the beginning of the second stage of labor. The fetal head position, station by means of angle of progression and head-to-perineum distance, and attitude by means of CCA were assessed using transabdominal or transperineal ultrasound. The primary outcome was persistent OP position at birth.

RESULTS

Between January and July 2022, 76 women were included in the study. There were 48 (63.2%) spontaneous rotations of the fetal head and spontaneous vaginal delivery occurred in all. Among the 28 (36.8%) fetuses that did not rotate spontaneously into an occiput anterior position, eight (28.6%) had a spontaneous vaginal delivery, while operative vaginal delivery and Cesarean delivery was performed in 11 (39.3%) and nine (32.1%) cases, respectively. Multivariable logistic regression analysis showed that the CCA (adjusted odds ratio (aOR), 2.15 (95% CI, 1.22-3.78); P = 0.008) and nulliparity (aOR, 0.20 (95% CI, 0.06-0.76); P = 0.02) were associated independently with persistent OP position at birth. Moreover, the CCA showed an area under the receiver-operating-characteristics curve of 0.69 (95% CI, 0.56-0.82); P = 0.005) for the prediction of persistent OP position. The optimal cut-off value of the CCA was 36.5°, and was associated with a sensitivity of 0.82 (95% CI, 0.63-0.94), specificity of 0.50 (95% CI, 0.35-0.65), positive predictive value of 0.49 (95% CI, 0.34-0.64), negative predictive value of 0.83 (95% CI, 0.64-0.94), positive likelihood ratio of 1.64 (95% CI, 1.18-2.29) and negative likelihood ratio of 0.36 (95% CI, 0.15-0.83).

CONCLUSIONS

Our data show that, within a population of women with fetal OP position at the beginning of the second stage of labor, the sonographic fetal head attitude measured by means of the CCA might help in the identification of fetuses at risk of persistent OP position. Such findings can be useful for patient counseling when OP position is diagnosed at full cervical dilatation. Further studies should investigate if the CCA might select patients who may benefit from manual rotation of the fetal head. © 2023 The Authors. Ultrasound in Obstetrics & Gynecology published by John Wiley & Sons Ltd on behalf of International Society of Ultrasound in Obstetrics and Gynecology.

Do neonatal birth weight thresholds for labor dystocia outcomes differ between short and normal stature women?

OBJECTIVE

To determine if there is a correlation between maternal short stature and neonatal birth weight among women with adverse outcomes related to labor dystocia.

METHODS

The medical records of singleton deliveries with adverse obstetric outcomes related to labor dystocia during 2014-2020, in a single tertiary center, were reviewed. Outcomes included at least one of the following: cesarean delivery (CD) due to cephalopelvic disproportion (CPD), prolonged second stage, shoulder dystocia, third- or fourth-degree perineal tear. Maternal short stature was defined as height below the 10th centile (short stature group) and normal stature was defined as maternal height between the 10th and 90th centiles (normal stature group). Maternal and neonatal characteristics were compared between the groups.

RESULTS

A total of 3295 women were included, among them, 307 in the short stature group (9.3%, height 1.52 ± 0.02 m) and 2988 in the normal stature group (90.7%, height 1.63 ± 0.04 m). Evaluating the entire cohort revealed similar neonatal birth weights comparing the short and normal stature groups. A subgroup analysis of women after CD due to CPD (n = 296) revealed lower neonatal birth weights in the short stature group (n = 31) compared with the normal stature group (n = 265) (3215 ± 411 vs 3484 ± 427 g, P = 0.001, respectively). Multivariable linear regression was performed for women who underwent CD due to CPD. After adjusting for obesity and diabetes mellitus, short stature and nulliparity were found to be independently associated with decreased neonatal birth weight (266 g less for short stature, P = 0.001, and 294 g less for nulliparity, P = 0.001).

CONCLUSIONS

Among women with short stature, CD due to CPD occurs at lower neonatal birth weights.

Correlation between bituberous diameter and mode of delivery in a cohort of low-risk nulliparous women

OBJECTIVE

The aim our study was to evaluate the association between the antepartum clinical measurement of the Bituberous Diameter (BTD) and the occurrence of unplanned obstetrical intervention (UOI) due to labor dystocia, including either operative vaginal delivery or caesarean section in a cohort of low-risk, nulliparous at term.

DESIGN

Retrospective analysis of prospectively collected data.

SETTING

Tertiary maternity care.

INTERVENTIONS

With the women lying in lithotomic the distance between two ischial tuberosities was assessed using a tape measure during the routine antenatal booking between 37 and 38 weeks of gestation.

MEASUREMENTS AND FINDINGS

Overall, 116 patient were included, and of these 23(19.8%) were submitted to an UOI due to labor dystocia. Compared to women that had a spontaneous vaginal delivery, women submitted to an UOI had a shorter BTD (8.25 + 0.843 vs 9.60 + 1.12, p < 0.001), a higher frequency of epidural analgesia (21/23 or 91.3% vs 50/93 or 53.8%; p = 0.002) and of augmentation of labor (14/23 or 60.9% vs 19/93 or 20.4%; p < 0.001) as well as a longer first [455 (IQR 142-455 min vs 293 (IQR 142-455) min] and second stages of labor [129 (IQR 85-155) min vs 51 (IQR 27-78) min]. Multivariable logistic regression showed that the BTD (aOR 0.16, 95% CI 0.04-0.60; p = 0.007) and the length of the second stage of labor (aOR 6.83, 95% CI 2.10-22.23; p = 0.001) were independently associated with UOI. When evaluating the diagnostic accuracy of the BTD for the prediction of UOI due to labor dystocia, the BTD showed an AUC of 0.82 (95 %CI 0.73-0.91; p < 0.001) with an optimal cut-off value of 8.6 cm (78.3% (95 %CI 56.3-92.5) sensitivity, 77.4% (95 %CI 67.6-85.4) specificity, 46.2% (95% CI 30.1-62.8) PPV, 93.5% (95% CI 85.5-97.9) NPV, 3.5 (95% CI 2.3-5.4) positive LR, and 0.28 (95% CI 0.13-0.61) negative LR. A significant inverse correlation between the length of the second stage of labour and the BTD in patients that had a vaginal delivery was also demonstrated (Spearman's rho = -0.24, p = 0.01).

KEY CONCLUSIONS

Our study suggests that antepartum clinical assessment of the BTD might be used as a reliable predictor of UOI due to labor dystocia in low-risk, nulliparous women at term gestation.

IMPLICATIONS FOR PRACTICE

Antenatal identification of women at higher risk for labor dystocia might trigger some interventions during the second stage of labor, such as maternal position shifting, to increase the pelvic capacity and potentially improve outcomes or might prompt a referral of the patient to a district hospital prior to the onset of labor.