Five years to the term breech trial: the rise and fall of a randomized controlled trial

Induction of labor in breech presentation at term: a retrospective cohort study

OBJECTIVE

To compare the outcome of two methods of labor induction and spontaneous onset of labor in breech presentation at term.

MATERIAL

A retrospective study between 2003 and 2012. We compare obstetric (indication of induction, Bishop score, cesarean rate) and perinatal outcomes (Apgar score, umbilical artery pH, base excess ≤-12 mmol/L, admission to neonatal unit) between prostaglandins and oxytocin. We also compare labor induction versus spontaneous onset of labor.

RESULTS

Of the 1684 breech deliveries, we carried out labor induction in 221 cases (76% with prostaglandins, 24% with oxytocin). The prostaglandins group had significantly lower Bishop scores and the time for induction phase was significantly higher. There were no differences in cesarean rate between both methods of induction or spontaneous onset of labor. The prostaglandins group had higher rates of base excess ≤-12 mmol/L. Compared with spontaneous onset of labor in breech presentation, induction had significant lower rates of newborn weight and higher rates of admission to the neonatal unit.

CONCLUSIONS

Induction of labor in breech presentation at term is a reasonable and effective option after a careful selection of cases. It was not associated with an increase of perinatal morbidity or cesarean rate compared with spontaneous onset of labor.

Breech presentation at term and associated obstetric risks factors-a nationwide population based cohort study

PURPOSE

The aim of this study was to estimate whether breech presentation at term was associated with known individual obstetric risk factors for adverse fetal outcome.

METHODS

This was a retrospective, nationwide Finnish population-based cohort study. Obstetric risks in all breech and vertex singleton deliveries at term were compared between the years 2005 and 2014. A multivariable logistic regression model was used to determine significant risk factors.

RESULTS

The breech presentation rate at term for singleton pregnancies was 2.4%. The stillbirth rate in term breech presentation was significantly higher compared to cephalic presentation (0.2 vs 0.1%). The odds ratios (95% CIs) for fetal growth restriction, oligohydramnios, gestational diabetes, a history of cesarean section and congenital fetal abnormalities were 1.19 CI (1.07-1.32), 1.42 CI (1.27-1.57), 1.06 CI (1.00-1.13), 2.13 (1.98-2.29) and 2.01 CI (1.92-2.11).

CONCLUSIONS

The study showed that breech presentation at term on its own was significantly associated with antenatal stillbirth and a number of individual obstetric risk factors for adverse perinatal outcomes. The risk factors included oligohydramnios, fetal growth restriction, gestational diabetes, history of caesarean section and congenital anomalies.

The Ten-Group Robson Classification: A Single Centre Approach Identifying Strategies to Optimise Caesarean Section Rates

Caesarean section (CS) rates have been increasing worldwide and have caused concerns. For meaningful comparisons to be made World Health Organization recommends the use of the Ten-Group Robson classification as the global standard for assessing CS rates. 2625 women who birthed over a 12-month period were analysed using this classification. Women with previous CS (group 5) comprised 10.9% of the overall 23.5% CS rate. Women with one previous CS who did not attempt VBAC contributed 5.3% of the overall 23.5% CS rate. Second largest contributor was singleton nulliparous women with cephalic presentation at term (5.1% of the total 23.5%). Induction of labour was associated with higher CS rate (groups 1 and 3) (24.5% versus 11.9% and 6.2% versus 2.6%, resp.). For postdates IOL we recommend a gatekeeper booking system to minimise these being performed <41 weeks. We suggest setting up dedicated VBAC clinic to support for women with one previous CS. Furthermore review of definition of failure to progress in labour not only may lower CS rates in groups 1 and 2a but also would reduce the size of group 5 in the future.

Supporting Women Planning a Vaginal Breech Birth: An International Survey

OBJECTIVE

The aim of this study was to explore the experiences of women who planned a vaginal breech birth.

METHOD

An online survey was developed consisting of questions regarding women's experiences surrounding planned vaginal breech birth. The survey was distributed between April 2014 and January 2015 to closed membership Facebook groups that had a consumer focus on vaginal breech birth.

RESULTS

In total, 204 unique responses to the survey were obtained from women who had sought the option of a vaginal breech birth in a previous pregnancy. Most women (80.8%) stated that they were happy with the birth choices they made, and a significant proportion (89.4%) would attempt a vaginal breech birth in subsequent pregnancies. Less than half of women were formally referred to a clinician skilled in vaginal breech birth when their baby was diagnosed breech (41.8%), while the remainder sourced a clinician themselves. Half of the women felt supported by their care provider (56.7%) and less than half (42.3%) felt supported by family and friends.

CONCLUSION

The women who responded to this international survey sought the option of a vaginal breech birth, were subsequently happy with this decision, and would attempt a vaginal breech birth in their next pregnancy. Access to vaginal breech birth is important for some women; however, this choice may be challenging to achieve. Consistent information and support from clinicians is important to assist decision-making.

Risk factors for emergency caesarean section in planned vaginal breech delivery

PURPOSE

To identify risk factors for emergency caesarean section in women attempting a vaginal breech delivery at term.

METHODS

Data from 1092 breech deliveries performed between 1998 and 2013 at a Swiss cantonal hospital were extracted from an electronic database. Of the 866 women with a singleton, full term pregnancy, 464 planned a vaginal breech delivery. Fifty-seven percent (265/464) were successful in delivering vaginally. Multivariate regression analyses of risk factors were performed, and neonatal and maternal complications were compared.

RESULTS

Risk factors for failed vaginal delivery were peridural anaesthesia (OR 2.05; 95 % CI 1.09-3.84; p = 0.025), nulliparity (OR 2.82; 95 % CI 1.87-4.25; p < 0.001), high birth weight (OR 1.17; 95 % CI 1.04-1.30; p = 0.006) and induction of labour (OR 1.56; 95 % CI 1.003-2.44; p = 0.048). Maternal age, height and weight; gestational age; or newborn length and head circumference were not associated with an unplanned caesarean section. The rate of successful vaginal delivery in the low risk sub-group (multiparous women without induction of labour) was 58-83 %, depending on birth weight category. The likelihood of success for the high risk sub-group (nulliparous women with induction of labour) fell below a third at neonatal birth weights >3250 g. Complication rates were low in the cohort.

CONCLUSIONS

Use of peridural anaesthesia, nulliparity, high birth weight and induction of labour were risk factors for unsuccessful vaginal breech delivery requiring an unplanned caesarean section. Awareness of these risk factors is useful when counselling women who are considering a vaginal breech delivery.

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

Management of breech presentation at term: a retrospective cohort study of 10 years of experience

OBJECTIVE

To evaluate the impact of management of childbirth (external cephalic version (ECV) plus planned vaginal delivery (PVD)) of breech presentation at term (⩾37 weeks of gestation).

STUDY DESIGN

This retrospective cohort study was based on data collected of singleton breech presentations at term in the Obstetrics and Gynaecology Service, Cruces University Hospital (Biscay, Spain), from January 2003 to December 2012.

RESULT

We attended 2377 singleton breech pregnancies at term. We attended 1684 singleton breech term deliveries, attempting vaginal delivery after selection in 52.9% of cases and were successful in 57.5% of attempts. A total of 1360 ECV were attempted, with a success rate of 50.3% of those attempted. The use of ECV has decreased the rate of breech presentation at delivery by 39.0%, the rate of breech presentation as a caesarean section (CS) indication by 47.1% (CS due to breech presentation/total of CS) and the rate of CS for breech presentation out of the total of deliveries by 39.1% (CS due to breech presentation/total of deliveries). Early postnatal parameters (5-min Apgar score, umbilical cord arterial pH and acid-base analysis) were significantly lower following PVD compared with planned CS for breech presentation. However, we did not find any differences in the rates of admissions to the neonatal unit or neonatal mortality.

CONCLUSION

Management of breech presentation with a protocol that includes ECV, careful selection criteria and active management of vaginal delivery achieve a great decrease in the rate of CS for breech presentation.

[Can we decrease cesarean rate at a university hospital treating high risk pregnancies?]

OBJECTIVE

To determine which clinical practice changes were responsible for a decrease in cesarean rate from 19.2% in 2003 to 15.5% in 2012 at our university hospital treating high risk pregnancies, while verifying the absence of any increase in neonatal morbidity and death.

MATERIALS AND METHODS

A descriptive retrospective study was undertaken at our labour ward including all patients delivering in 2003 and in 2012. Maternal, obstetrical and neonatal characteristics of the two populations were compared. Cesarean rates were analysed following : (1) Robson classification, (2) some maternal and obstetrical characteristics, and (3) indications for cesarean.

RESULTS

Mean age, BMI and rate of scarred uterus significantly increased in 2012. The two populations remained comparable in terms of other criteria studied. The main cause responsible for decrease in cesarean rate was breech presentations (p<0.05). Furthermore, significantly less cesareans were performed after labour induction (p=0.04). We also significantly decreased our elective cesarean rate by more than 3% without increasing cesarean sections during labour, showing a rise in successful vaginal delivery trials. The impact of in utero transfers on the global rate of cesarean is highly significant since the latter has been divided by half in 10 years in this population considered to be of high risk for cesareans.

DISCUSSION

These significant decreases reflect our experience in allowing vaginal deliveries in breech presentations, and also a better selection of patients for labour induction. Furthermore, it should be noted that increasing vaginal delivery trials in various obstetrical situations participated in this decrease. We clearly found that some indications for elective cesarean can be avoided, such as multiple pregnancies and scarred uterus, thus showing the importance of restricting the first indication for cesarean. Finally, the decrease in cesarean rate had no negative effect on neonatal outcome.

CONCLUSION

Decreasing cesarean rate is possible in a university hospital treating high risk pregnancies. It requires daily obstetrical case by case critical analysis, allowing wide acceptance of vaginal delivery trials, and continuously evaluating clinical practices.

Once more unto the breech: planned vaginal delivery compared with planned cesarean delivery

This article provides a knowledge-based assessment of planned cesarean delivery compared with planned vaginal delivery for breech presentation at term gestation. The most critical evidence on this issue is the intention-to-treat analysis from the Term Breech Trial, which showed that planned cesarean delivery reduced composite perinatal death and serious neonatal morbidity. Although there was no difference in composite death or neurodevelopmental delay at 2 years of age, this finding was based on only 44% of randomized patients and was not an analysis by intention to treat. On the other hand, the design of the nonexperimental Presentation et Mode d'Accouchement: presentation and mode of delivery (PREMODA) study (which showed no difference in composite perinatal mortality or morbidity after planned cesarean delivery compared with planned vaginal delivery), likely favored the planned vaginal delivery group; lack of exclusion criteria led to higher risk women (with contraindications to vaginal delivery) being included in the planned cesarean delivery group. Such selection bias notwithstanding, both the Term Breech Trial and the PREMODA study showed significantly higher rates of 5-minute Apgar score less than 4, 5-minute Apgar score less than 7, intubation, and birth trauma in the planned vaginal delivery group. Finally, studies from the Netherlands, Denmark, and Canada have shown that increases in planned cesarean delivery after the Term Breech Trial led to improved neonatal outcomes. Nevertheless, planned vaginal delivery continues to be associated with higher rates of adverse perinatal outcomes in these countries. The totality of the evidence therefore unequivocally shows the relatively greater safety of planned cesarean delivery for breech presentation at term gestation.

Women's experiences of planning a vaginal breech birth in Australia

Background

In many countries, planned vaginal breech birth (VBB) is a rare event. After the Term Breech Trial in 2000, VBB reduced and caesarean section for breech presentation increased. Despite this, women still request VBB. The objective of this study was to explore the experiences and decision-making processes of women who had sought a VBB.

Methods

A qualitative study using descriptive exploratory design was undertaken. Twenty-two (n = 22) women who planned a VBB, regardless of eventual mode of birth were recruited. The women had given birth at one of two maternity hospitals in Australia that supported VBB. In-depth, semi-structured interviews using an interview guide were conducted. Interviews were analysed thematically.

Results

Twenty two women were interviewed; three quarters were primiparous (n = 16; 73%). Nine (41%) were already attending a hospital that supported VBB with the remaining women moving hospitals. All women actively sought a vaginal breech birth because the baby remained breech after an external cephalic version – 12 had a vaginal birth (55%) and 10 (45%) a caesarean section after labour commenced. There were four main themes: Reacting to a loss of choice and control, Wanting information that was trustworthy, Fighting the system and seeking support for VBB and The importance of ‘having a go’ at VBB.

Conclusions

Women seeking a VBB value clear, consistent and relevant information in deciding about mode of birth. Women desire autonomy to choose vaginal breech birth and to be supported in their choice with high quality care.

Educational outcomes following breech delivery: a record-linkage study of 456947 children

BACKGROUND

Obstetric management of term breech infants changed dramatically following the Term Breech Trial which suggested increased serious neonatal morbidity following trial of labour. Short-term morbidity is a poor proxy of long-term neurological sequelae. We determined whether vaginal breech delivery was associated with educational outcomes.

METHODS

We linked three Scotland-wide administrative databases at an individual level: the ScotXed school census; Scottish Qualifications Authority (SQA) examination results; and Scottish Morbidity Record (SMR02) maternity database. The linkage provided information on singleton children, born at term, attending Scottish schools between 2006 and 2011.

RESULTS

Of the 456 947 eligible children, 1574 (0.3%) had vaginal breech deliveries, 12 489 (2.7%) planned caesarean section for breech presentation and 442 090 (96.9%) vaginal cephalic deliveries. The percentage of term breech infants delivered vaginally fell from 23% to 7% among children who started school in 2006 and 2011, respectively. Of children born by vaginal breech delivery, 1.5% had a low 5-min Apgar score (≤3) compared with only 0.4% of those born by either breech caesarean section [adjusted odds ratio (OR) 6.16, 95% confidence interval (CI) 4.44-8.54, p<0.001] or cephalic vaginal delivery (adjusted OR 3.84, 95% CI 2.99-4.93, p<0.001). Children born by vaginal breech delivery had lower examination attainment than those born by either planned caesarean section for breech presentation (adjusted OR 1.16, 95% CI 1.02-1.32, p=0.020) or vaginal cephalic delivery (adjusted OR 1.14, 95% CI 1.01-1.28, p=0.029).

CONCLUSIONS

Vaginal delivery of term breech infants was associated with lower examination attainment, as well as poorer Apgar scores, suggesting that the adverse effects are not just short-term.

Can Caesarean section improve child and maternal health? The case of breech babies

This paper examines the health effects of Caesarean section (CS) for children and their mothers. We use exogenous variation in the probability of CS in a fuzzy regression discontinuity design. Using administrative Danish data, we exploit an information shock for obstetricians that sharply altered CS rates for breech babies. We find that CS decreases the child's probability of having a low APGAR score and the number of family doctor visits in the first year of life. We find no significant effects for severe neonatal morbidity or hospitalizations. While mothers are hospitalized longer after birth, we find no effects of CS for maternal post-birth complications or infections. Although the change in mode of delivery for the marginal breech babies increases direct costs, the health benefits show that CS is the safest option for these children.

Obstetric anesthesia: not just for cesareans and labor

The scope of obstetric anesthesia practice ranges far beyond the delivery of care to women for vaginal and cesarean deliveries. Increasingly, obstetric anesthesiologists are involved in the management of anesthetics for new procedures and for new indications. Anesthesia is frequently needed for maternal procedures, as well as fetal procedures, and at varying times in the intrapartum period. Maternal-specific procedures include cerclage, external cephalic version (ECV), postpartum bilateral tubal ligation (BTL), and dilation and evacuation (D and E). Fetus-specific procedures include fetoscopic laser photocoagulation and ex-utero intrapartum treatment (EXIT). This review will not include discussion of the anesthetic management of non-obstetric surgery during pregnancy, such as appendectomy or cholecystectomy.

Twin Birth Considering the Current Results of the "Twin Birth Study"

The rate of caesarean sections in multiple births has grown sharply worldwide. The reason for this may be the results of large retrospective cohort studies from the 1990s, which displayed an increased risk of mortality and morbidity, especially for the second twin, in the case of vaginal births. Multiple monocentric analyses have not been able to confirm this. As a prospective, multi-centre randomised study, the Twin Birth Study published in 2013, in which 105 clinics in 25 countries took part, showed that, under optimum conditions, there was no difference in neonatal and maternal mortality and morbidity if the birth was planned to be vaginal or via caesarean. Detailed analyses, which would be helpful in choosing the type of birth method and obstetric management in the event of vaginal birth, have not previously been published. Retrospective studies must be referred to for this.

Comparison of fetal outcome in premature vaginal or cesarean breech delivery at 24-37 gestational weeks

PURPOSE

To compare the fetal outcome of preterm breech infants delivered vaginally (VD) or by cesarean section (CS).

METHODS

A monocentric, retrospective consecutive case series of preterm breech deliveries between 24-37 gestational weeks over 10 years from 1/2000 to 12/2009 was performed in a perinatal care center (Level 1) at the University Clinic of Salzburg, Austria. Data from hospital database were statistically analyzed and compared regarding birth weight, head circumference, parity, transfer rate to neonatal intensive care unit (NICU), arterial and venous cord blood pH and base excess (BE), arterial cord blood pH ≤ 7.10 and BE ≤ -11. Special focus was on fetal outcome of elective CS preterm breech deliveries with a non-urgent medical indication compared to VD.

RESULTS

Among 22.115 deliveries, there were 346 live-born preterm singletons and twins in breech presentation (1.56 %), born between 24 + 0 and 37 + 0 gestational weeks. 180 CS and 36 vaginally delivered preterm breech infants were statistically evaluated. On comparing CS vs. VD for premature breech singletons, arterial cord blood pH and BE were lower in the VD group. VD twins had a lower arterial cord blood pH than CS twins. All other parameters were comparable. In preterm breech singletons with non-urgent CS, a statistical analysis was not possible due to small numbers. The VD twin group revealed lower values in birth weight, head circumference, arterial cord blood pH and BE, but no significant difference in venous cord blood pH and BE and transfer rate to NICU.

CONCLUSIONS

Although general recommendations regarding a superior mode of delivery for improved fetal outcome of preterm breech infants cannot be given, these data do not support a policy of routine CS.

Signal quality of non-invasive fetal electrocardiogram in vaginal breech delivery: a case-controlled study

OBJECTIVE

Recently, a non-invasive fetal electrocardiogram monitor has been approved for clinical usage in labour and delivery. To determine the fetal signal quality of vaginal breech deliveries in comparison with a case-controlled cephalic group during labour.

STUDY DESIGN

This case-control study was carried out at the Department of Obstetrics and Gynecology of the University Hospital Frankfurt between 1st July 2012 and 30th September 2012. A total of seven breech deliveries were evaluated. A case-controlled cephalic group with same gestational age and parity were selected from a previous trial.

RESULTS

During first stage of labour, vaginal breech and cephalic delivery had no significant different fetal signal success rates (mean 87.8 vs. 85.7 %; p > 0.05). There was a trend of higher fetal signal success rates in the vaginal breech delivery group during second stage of labour (78.4 vs. 55.4 %; p = 0.08).

CONCLUSION

Similar fetal signal success rates in vaginal breech delivery in comparison to cephalic presentation were demonstrated using the new commercially available non-invasive abdominal fECG device (the Monica AN24(TM)).

[Breech delivery and scarred uterus: a special obstetrical situation?]

AIM

The management of breech delivery in patients with a history of caesarean section is a special situation requiring to anticipate the delivery route if the usual prerequisites for the acceptance of vaginal breech delivery are present. Does a history of caesarean section imply a systematic refusal of vaginal delivery in case of breech presentation or an alternative to an iterative caesarean still exists?

MATERIALS AND METHODS

An observational study was undertaken in our level III labour ward from January 1st 1994 to June 30th 2010 on 91 patients with a history of caesarean section and who had breech deliveries of singleton pregnancies at more than 35weeks of amenorrhea. Maternal, obstetrical and neonatal parameters were collected. Patients were divided into three groups: vaginal delivery, caesarean section after an accepted vaginal birth trial, elective caesarean section.

RESULTS

The rate of an accepted vaginal birth trial was 24.2% (22 cases) with a 36.4% (eight patients) success rate in this group. There were two (2.9%) unplanned vaginal births. Fourteen patients (15.4%) had caesarian sections after an accepted vaginal birth trial: ten before labour and four during labour for dynamic dystocia or non-reassuring fetal status. Most caesarean sections before labour in case of an accepted vaginal birth trial were justified by an intercurrent factor requiring induction of labour. Neonatal factors did not show any increased morbidity or mortality in the vaginal birth group. No Apgar score was found to be less than or equal to 7 at 5minutes. Umbilical arterial pH and lactate measured as from 2001 were similar between the groups. Indeed, the mean arterial pH after vaginal birth was 7.19 as compared to 7.22 in case of caesarean section after an accepted vaginal birth trial, and 7.26 after elective caesarean section. Likewise, the mean lactate measurement was at 4.71mmol/L after vaginal birth versus 4.54 and 3.07 in the other two groups. Only neonates born after elective caesarean sections were transferred to intensive care (four cases).

CONCLUSION

Vaginal breech delivery in case of a scarred uterus is possible, if each obstetrical situation is correctly studied to authorize a vaginal birth trial after a careful selection of patients and a strict management of labour. Vaginal birth does not seem to increase maternal and neonatal morbidity and mortality in this situation.

The incidence of caesarean sections in the university clinical center of kosovo

Introduction:

As in most countries of the world also at Kosovo the rate of Cesarean section from year to year is increasing.

Aim:

The main purpose of this paper was to present the incidence of births completed by Caesarean section at the Clinic of Gynecology and Obstetrics of University Clinical Center of Kosovo in Prishtinë.

Material and methods:

This study is retrospective, namely its made by collecting epidemiological data from patients’ histories that completed birth by Caesarean section for the period 2000-2006 in this clinic.

Results and discussion:

During this period, 14 maternal deaths were recorded during or after Caesarean section. Besides this, 14 lethal outcomes, the object of our study was 84 mothers which completed birth by Caesarean section and which are best used as a control group. The average age of mothers who died during or after Caesarean section was 32.1 years (SD ± 4.9). Youngest in this group was 24 years old and oldest 42 years. While the average age of mothers from the control group was 30.6 years (SD ± 5.9). Youngest was 19 and oldest 43 years, without significant difference. Most mothers included in the survey had more than one indication for Caesarean section. The most frequent indication was PIH syndrome with 33.7% and previous Caesarean section in 32.7%. Then with the participation of 12.2% were abruption of the placenta and disproportio feto pelvinea, 11.2% pelvinea and placenta praevia presentation, 10.2% parturiens while other indications were much rarer with less than 10% participation.

Conclusion:

Based on this we can conclude that the risk of the Caesarean section is high.

Randomised controlled trials and clinical maternity care: moving on from intention-to-treat and other simplistic analyses of efficacy

BACKGROUND

The obstetrical literature is dominated by Randomised Controlled Trials (RCTs), with the vast majority being analysed using an intention-to-treat (ITT) approach. Whilst this approach may reflect well the consequence of assignment to therapy and hence the 'trialists'perspective', it may fail to address the consequence of actually receiving therapy (the patient's perspective).

DISCUSSION

This review questions the ubiquitous adherence to the ITT approach, and gives examples of where this may have misled the maternity care professions. It gives an overview of techniques to overcome potential deficiencies in result presentation, using method effectiveness models such as 'Per Protocol' (PP) or 'As-Treated' (AT) that may give more accurate clinical meaning to the presentation of obstetrical results. It then proceeds to cover the added benefits, considerations and potential pitfalls of the use of Instrumental Variable (IV) models in order to better reflect the clinical context.

SUMMARY

While ITT may achieve statistical purity, it frequently fails to address the true clinical or patient's perspective. Though more complex and potentially beset by problems of their own, alternative methods of result presentation may better serve the latter aim. Each of the other methods may rely on untestable assumptions and therefore it is wisest that study results are presented in multiple formats to allow for informed reader evaluation.