Prediction of caesarean section from ultrasound and clinical assessment of fetal size

Caesarean sections are associated with sonographic determined fetal size from the second trimester onwards

Human birth represents a critical and life-threatening event in the life of mother and child and is therefore of special importance for anthropological as well as public health research.

Study aims: to analyze the association patterns between fetal biometry and delivery modes from the first trimester onwards.

In this electronic medical record-based study, a dataset of 3408 singleton term birth taking place at the Viennese Danube hospital in Austria. was analyzed. Fetal biometry was reconstructed by the results of three ultrasound examinations carried out at the 11th/12th, 20th/21th and 32th/33thweek of gestation. In detail, crown-rump length, biparietal diameter, fronto-occipital diameter, head circumference, abdominal trans-verse diameter, abdominal sagittal diameter, abdominal circumference, and femur length were determined. Birth weight, birth length and head circumference were measured immediately after birth. Four delivery modes were compared: spontaneous vaginal birth, instrumental vaginal birth, planned cesarean section and emergency cesarean section.

The total cesarean section rate was 10.2%. Fetal biometry and newborn size differed significantly between the four delivery modes. From the second trimester onward, head circumferences were significantly larger (p=0.005) among fetuses delivered by instrumental delivery or emergency cesarean section than among fetuses delivered by spontaneous vaginal birth. The fetal abdominal dimensions during the third trimester were significantly largest (p=0.001) among fetuses delivered by emergency cesarean section. In comparison to spontaneous vaginal delivery the risk to require instrumental delivery increased significantly with increasing fetal head dimensions at the second (p=0.019) and third trimester(p=0.032) independent of maternal somatic factors. The risk of emergency CS increased significantly with increasing head dimensions (p=0.030) as well as abdominal dimensions (p=0.001) at the third trimester and newborn size (p=0.002), also independently of maternal somatic factors.

In general, larger fetuses are on an increased risk of experiencing instrumental delivery or emergency caesarean section. This association between fetal size and delivery mode is detectable from the second trimester onwards.

Is ultrasound measured fetal biometry predictive of intrapartum caesarean section for failure to progress?

BACKGROUND

There are global concerns regarding excessive caesarean rates, which could be reduced by identification of risk factors leading to preventative measures such as induction of labour.

AIMS

This study aims to describe the association between antenatal ultrasound and emergency caesarean section for: (i) failure to progress; (ii) other indications; and (iii) any indication.

MATERIALS AND METHODS

Women who had an ultrasound in pregnancy between 36^(+0/7) to 38^(+6/7) weeks at Royal Prince Alfred Hospital from January 2005 to June 2009 were included. Ultrasound parameters were linked to clinical parameters from the maternity database. Missing clinical data were imputed and multiple logistic regression performed.

RESULTS

Fetal biometry data were available for 2006 pregnancies. After adjusting for maternal age, height, body mass index, parity, previous caesarean section and diabetes, caesarean section for failure to progress was associated with estimated fetal weight (odds ratio (OR) 2.24 (95% CI: 1.76-2.84) per 500 g increase); or biparietal diameter (OR 1.51 (1.16-1.97) per 5 mm increase) and abdominal circumference (OR for the 4th quartile (>75th centile) compared with the 10-25th centile group was 2.09 (1.13-3.85)).* There were also non-linear associations between components of fetal biometry and caesarean section for fetal distress and for any indication.

CONCLUSIONS

Components of fetal biometry in the third trimester are associated with intrapartum caesarean section for failure to progress. These parameters could be incorporated into models to predict emergency caesarean section which could lead to implementation of preventative strategies. *[Corrections added on 29 January 2018, after first online publication, '(OR for the 4th quartile (>7th centile)' has been changed to '(OR for the 4th quartile (>75th centile)'.].

Ultrasound and clinical predictors for Caesarean delivery after labour induction at term

OBJECTIVE

To assess the relationship of ultrasound assessment for amniotic fluid, fetal weight, cervical length, cervical funneling and clinical factors on the risk of Caesarean delivery after labour induction at term.

METHODS

On hundred and fifty-two women scheduled for labour induction at term agreed to participate. Sonography was performed to obtain fetal biometry, amniotic fluid index and cervical length and to detect funneling at the internal cervical os. The sonographic findings were concealed. Study women received standard care during labour induction.

RESULTS

On univariate analysis using Fisher's exact test, parity, cervical length and Bishop score were associated with Caesarean delivery. Following multivariable logistic regression analysis, only nulliparity (adjusted odds ratio (AOR) 5.2 (95% CI 2.2-12.2): P<0.001) and transvaginal ultrasound-determined cervical length of more than 20 mm (AOR 2.8 (95% CI 1.0-7.4): P=0.04) were independent predictors of Caesarean delivery in labour induction. Maternal age, maternal height, gestational age, indication for labour induction, amniotic fluid index, cervical funneling and ultrasound-estimated fetal weight did not predict Caesarean delivery.

CONCLUSION

In women who had undergone labour induction at term with a singleton fetus, nulliparity and cervical length of more than 20 mm on transvaginal sonography were independent predictors of Caesarean delivery. This information is helpful for pre-induction counselling.

Cephalopelvic disproportion is associated with an altered uterine contraction shape in the active phase of labor

OBJECTIVE

The purpose of this study was to determine if intrapartum contractions of a particular shape (rapid rise with slower return to baseline) are predictive of cephalopelvic disproportion (CPD).

STUDY DESIGN

In an institutional review board (IRB)-approved study, cohorts of 100 women who underwent spontaneous vaginal delivery (SVD) and 100 who underwent cesarean section (C/S) for CPD or arrest of labor were consecutively identified between January 2004 and March 2005. Inclusion criteria included term, singleton pregnancies, nulliparity, and absence of fetal anomalies. One hour of interpretable electronic fetal monitoring (EFM) was obtained in active labor. Fall to rise (F:R) ratio was calculated by measuring the time for a contraction to return to its baseline from its peak ("fall") and the time for a contraction to rise to its peak ("rise"). The F:Rs were then averaged over the number of contractions. Data were analyzed using Student t test, Chi-square, and Fisher exact tests where appropriate.

RESULTS

Maternal demographics are listed in Table I. The average F:R ratio was 1.55 for SVD versus 1.77 for C/S, a statistically significant difference (P = .00003). Analysis of variance revealed this difference persists when controlled for the potentially confounding factors shown. At F:R >1.76, moreover, there was a trend towards larger birth weight (P = .06).

CONCLUSION

Our study demonstrates there is a difference in uterine contraction configuration that is more common in those labors destined for C/S due to CPD. This may indicate the presence of a heretofore unknown feedback mechanism as the uterus adapts to the dysfunctional labor.

Prediction of successful vaginal delivery in women undergoing external cephalic version at term for breech presentation

OBJECTIVE

The aim of this study is to evaluate the clinical and sonographic predictors of ultimate successful vaginal delivery in women undergoing external cephalic version.

STUDY DESIGN

The study population consisted of women with external cephalic version performed at or after 36 weeks of gestation. They were randomized into group A or B, each consisted of half of the total study population. Logistic regression was performed on group A to identify the significant independent variables in predicting successful cephalic vaginal delivery, which were used to construct a prediction model. The derived regression model was then tested in group B to assess its accuracy.

RESULTS

The study included 407 pregnancies. Maternal weight (kg) at the time of version, maternal height (cm), multiparity, engagement of fetal presenting part, and fetal head palpable were significant independent variables of successful version and vaginal delivery (regression coefficients are: -0.084, 0.085, 1.752, -1.271, and 0.725, respectively). A prediction model was constructed based on these independent variables. The weighted average of the overall accuracy in predicting success or failure of version and vaginal delivery was 70.9%. The regression model was then applied to study group B. Using 0.50 as the cutoff value, the sensitivity, specificity, positive, and negative predictive values were 75.4, 58.8, 73.7, and 61.0%, respectively.

CONCLUSION

A regression model constructed based on clinical variables failed to provide an accurate predictive tool of successful external cephalic version and vaginal delivery. However, in women who are equivocal about external cephalic version, a high prediction of success would be encouraging.

How effective is antenatal care in preventing maternal mortality and serious morbidity? An overview of the evidence

This is an overview of evidence of the effectiveness of antenatal care in relation to maternal mortality and serious morbidity, focused in particular on developing countries. It concentrates on the major causes of maternal mortality, and traces their antecedent morbidities and risk factors in pregnancy. It also includes interventions aimed at preventing, detecting or treating any stage along this pathway during pregnancy. This is an updated and expanded version of a review first published by the World Health Organization (WHO) in 1992. The scientific evidence from randomised controlled trials and other types of intervention or observational study on the effectiveness of these interventions is reviewed critically. The sources and quality of available data, and possible biases in their collection or interpretation are considered. As in other areas of maternal health, good-quality evidence is scarce and, just as in many aspects of health care generally, there are interventions in current practice that have not been subjected to rigorous evaluation. A table of antenatal interventions of proven effectiveness in conditions that can lead to maternal mortality or serious morbidity is presented. Interventions for which there is some promising evidence, short of proof, of effectiveness are explored, and the outstanding questions formulated. These are presented in a series of tables with suggestions about the types of study needed to answer them.