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\begin{document}

\title{The Soleymani and Collins Obstetric Morbidity Score (SaCOMS): a
quantitative tool for measuring maternal morbidity from complex
obstetric surgery such as placenta accreta spectrum (PAS)}



\author[1]{Sally Collins}%
\author[2]{Esme WEEKS}%
\author[3]{Hooman SOLEYMANI MAJD}%
\author[3]{Susan Addley}%
\author[4]{Angelo Cavallaro}%
\affil[1]{University of Oxford Nuffield Department of Women's \& Reproductive Health}%
\affil[2]{University of Oxford Medical Sciences Division}%
\affil[3]{University of Oxford Department of Oncology}%
\affil[4]{John Radcliffe Hospital}%


\vspace{-1em}



  
  \date{June 11, 2024}


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\selectlanguage{english}
\begin{abstract}
\textbf{Objective:} To describe a suggested version of the Clavien-Dindo
morbidity classification specific to obstetrics and employ it to build a
cumulative morbidity score which fully reflects the `patient
experience'. To demonstrate the utility of this novel system in a cohort
of women with Placenta Accreta Spectrum (PAS). ~ \textbf{Design:} Delphi
consensus and retrospective application of the resulting scores to
morbidity from PAS surgery. ~ \textbf{Setting:} UK Tertiary referral
centre for PAS. ~ \textbf{Population:} Women who had caesarean
hysterectomy for PAS. ~ \textbf{Methods:} The Clavien-Dindo
classification was modified to reflect obstetric procedures and a
quantitative morbidity measure, the Soleymani and Collins Obstetric
Morbidity Score (SaCOMS), was developed based on this. Both were then
validated using a Delphi consensus of experts in PAS and retrospectively
applied to a cohort of 54 women with PAS. ~ \textbf{Main Outcome
measures:} Delphi consensus of \textgreater{}80\%, binary outcome of
adverse event or not and quantitative values from the SaCOMS. ~
\textbf{Results:} Clinicians with expertise in PAS believe that the
Modified Obstetric Clavien-Dindo classification system and the novel
SaCOMS tool can improve assessment of maternal morbidity, and better
reflect the `patient experience'. Application to the PAS cohort
demonstrates that surgery by gynae-oncological surgeons may be
associated with decreased incidence and cumulative morbidity outcomes
for women with PAS, especially those with the most severe presentation.
~ ~ \textbf{Conclusions:} This study presents a clinically useful
obstetric-specific classification system for surgical morbidity. SaCOMS
also provides a quantitative reflection of the full patient- journey
experienced as a result of surgical complications enabling a more
patient-centred representation of morbidity.%
\end{abstract}%



\sloppy


\section*{Introduction}

{\label{introduction}}

Placenta Accreta Spectrum (PAS) is a rare condition carrying a high risk
of maternal morbidity and mortality1. Failure of the placenta to
separate spontaneously can cause severe, sometimes life-threatening,
haemorrhage2. Morbidity can arise as a result of blood loss and the
complex surgery required to treat PAS due to the neovascularity,
distorted anatomy and unusually friable tissues encountered. Many
different ways of managing PAS have been suggested including immediate
hysterectomy3, focal resection and intentional placental retention but
evidence regarding the safety of each remains limited4. Much of the
research in obstetrics, as with most medical specialties, aims to reduce
mortality and morbidity. Whilst mortality is binary outcome, accurate
assessment of maternal morbidity is hindered by a lack of a unified
classification system tailored to obstetrics. Obstetric procedures
incorporate a unique set of combined risks, including neonatal risks,
massive haemorrhage, iatrogenic injury to pelvic structures, and risks
from pregnancy-associated conditions such as eclamptic seizures5. All of
this occurs at the life-changing moment of entering parenthood with all
its associated demands and expectations. Most scientific studies focus
on outcomes either judged to be important by the healthcare provider,
such as admission to intensive care unit (ICU) or numerically appealing
such as estimated blood loss. Whilst these are undoubtably important
they do not fully represent the `patient experience' at this critical
moment in the mother's life. Admission to ICU is often used as a marker
of severe morbidity however, for the majority of women with PAS this is
usually a short stay as a result of acute massive transfusion. Is this
more `severe' than a lower urinary tract injury requiring long-term
catheterization, multiple investigations and repeated surgical
procedures? A quantitative morbidity score which takes into account not
only the severity of immediate issue, but also longer-term cumulative
morbidity, is desperately needed if we are to compare novel obstetric
procedures especially surgically challenging ones, such as management of
placenta accreta spectrum. The Clavien-Dindo classification is a
well-established functional score based on the interventions required to
manage surgical complications\textsuperscript{6}. The classification
focuses mainly on the therapeutic consequences of a complication
attempting to match the severity of different morbidities. It is well
accepted and utilised `\emph{as-is}' or in a modified form in several
surgical specialties, including general surgery7, urology8 and
oncology9, but is yet to be adapted for use in obstetrics. The aims of
this study were twofold: Firstly, to develop both a clinically useful
obstetric-specific morbidity classification system and a quantitative,
patient-centred system reflecting the full journey experienced by women
following any complication. The second aim was to demonstrate the
potential utility of the novel quantitative scoring system by performing
retrospective analyses to explore morbidity according to the type of
surgeon undertaking the PAS surgery.

\section*{Methods}

{\label{methods}}

\subsection*{The Modified Obstetric Clavien-Dindo
Classification}

{\label{the-modified-obstetric-clavien-dindo-classification}}

The original Clavien-Dindo classification classifies complications as
any deviation from the normal postoperative course\textsuperscript{10}.
Sequelae which are considered as `after-effects' of surgery inherent to
the procedure (for example infertility following hysterectomy) are
excluded from this classification. Adverse events are then stratified by
severity, with a focus on the corrective measures required to manage the
complication. Morbidity events are graded as follows: Grade I (least
severe), Grade II, Grade IIIa/b, and Grade IVa/b (most severe).
Modifications from the original Clavien-Dindo classification were made
to incorporate obstetric-specific considerations such as the increased
circulating volume seen in pregnancy, as this affects what might
reasonably considered `significant' versus `massive' blood transfusions.
This modified classification (see Table 1) also includes examples
tailored to complex obstetric procedures, including complicated lower
urinary tract injuries, insertion of nephrostomies and ureteric stents,
and hysteroscopy +/- resection of retained products of conception.
Admission to ICU is considered as an adverse event only when
necessitated due to organ dysfunction, thus reducing potential
confounding of data due pre-planned admission to ICU for observation
being erroneously reported as an adverse outcome without significant
illness or threat-to-life. This corrects for the differences in ICU
admission policies seen in different units and countries. Sepsis and
disseminated intravascular coagulopathy (DIC) can be assessed according
to different clinical guidelines. This modified obstetric classification
system uses the Third International Consensus Definitions for Sepsis and
Septic Shock (Sepsis-3)11 to occurrence of sepsis. Coagulation data
including platelet count, increase in fibrin markers, PTT and fibrinogen
level are used to assess for DIC as per the International Society of
Thrombosis and Haemostasis (ISTH) guidelines12,13. The Soleymani and
Collins Obstetric Morbidity Score (SaCOMS) The quantitative SaCOMS
simply attributes numerical values to each grade of morbidity defined by
the Modified Obstetrics Clavien-Dindo (Table 2). These are used to
produce a cumulative `overall morbidity score' for individual women. The
final total accounts for multiple morbidities and the need for delayed
or long-term corrective measures, such as returns to theatre for
reparative surgery. Examples of how this can be applied to demonstrate
the full impact on the woman of each morbidity are shown in Table 3.
Thus, the SaCOMS is presented as a quantitative reflection of the
overall `patient experience' resulting from any adverse outcome.

\subsection*{Modified Delphi Consensus}

{\label{modified-delphi-consensus}}

Acceptability of the Modified Obstetric Clavien-Dindo classification and
SaCOMS for clinical classification and quantitative assessment of
morbidity was assessed using a survey-based consultation of a panel of
PAS experts, all of whom were members of the International Society for
Placenta Accreta Spectrum (IS-PAS). The Modified Obstetric Clavien-Dindo
classification, the SaCOMS guidelines and two case examples
demonstrating the calculation of the quantitative cumulative SaCOMS
value (Table 3) were sent with an accompanying questionnaire. The
questionnaire used Likert-scale answer values to assess opinion on the
need for such an obstetrics-specific classification system, and the
suitability, utility and ease-of-use of the modified obstetric
Clavien-Dindo classification and SaCOMS to address such a need
(Supplementary Material 1). Free-text responses were also included to
facilitate an opportunity to improve either of the systems. An 80\%
selection of the two highest Likert-scale response options was set as
the threshold for approval. If 80\% was not reached, the item relating
to that question would be reviewed taking into account the comments of
the panel, the classification or score adapted, and the changed
documents resubmitted for approval until an 80\% approval score was
reached.

\subsection*{}

{\label{section}}

\subsection*{Retrospective Morbidity
Analysis}

{\label{retrospective-morbidity-analysis}}

Retrospective analysis of morbidity outcomes for women with PAS used
data collected for an audit examining the morbidities seen for all PAS
cases delivered at a UK Tertiary referral centre, between August 2011
and May 2019. Cases were classed as emergency or elective according to
the standard 1-4 categorisation stated in the National Institute for
Clinical Excellence (NICE) `Performing caesarean section' Guidelines14.
For the purposes of this cohort analysis, categories 1 and 2 were
considered `emergency' and categories 3 and 4 as `non-emergency' or
`elective'. This subdivision allows for the fact that delivery under
non-emergency circumstances, without maternal or fetal compromise, will
afford better preparation in terms of assembly of the MDT and operating
theatre resources leading to potentially better outcomes. Similarly,
cases were then further subdivided depending on whether PAS was
`suspected' antenatally (as confirmation of PAS diagnosis can only be
made at delivery). Antenatal suspicion of PAS is associated with better
maternal outcomes15, including blood loss16 and need for mass
transfusions17. For the purpose of comparing surgeon type with respect
to morbidity, only cases which were electively delivered and antenatally
suspected were considered in order to account for the adequate
preparation of an experienced MDT this affords. Finally, cases were
grouped according to the FIGO clinical classification of PAS18 as either
abnormally adherent (FIGO grade 1) or abnormally invasive (FIGO grades 2
and 3), to reflect clinical severity. Grades 2 and 3 result in greater
neovascularity, more friable tissues and placenta involving other pelvic
structures resulting in higher-risk surgical procedures, for example the
need for deliberate cystotomy to facilitate hysterectomy where the
posterior bladder wall cannot be detached from the anterior uterine
wall19. Several sources were used to collate data for each case
according to a predefined audit pro-forma. The Electronic Patient Record
(EPR) was used to determine patient age, gestation and BMI at time of
delivery. Physical and electronic operation notes were used to determine
surgical procedure, including lead surgeon, incision type, and any
surgical damage documented at the time. Immediate, short-term and
delayed morbidities according to the Modified Obstetric Clavien-Dindo
classification and SaCOMS were recorded from both the hospital and
primary practitioner's electronic patient records, including ITU
admission, long-term ureteric stents or subsequent corrective surgical
procedures. Total time in theatre, estimated blood loss, and use of cell
salvage were determined from anaesthetic charts and independent cell
salvage records. No ethical approval was needed for the morbidity
analysis as it formed part of an ongoing clinical audit and was
appropriately registered and approved as such by the local NHS clinical
governance team (OUH Audit Number 5544, approved 14/6/2019).

\subsection*{Quantification of
morbidity}

{\label{quantification-of-morbidity}}

Morbidities were identified and classified according to the Modified
Obstetric Clavien- Dindo classification and SaCOMS, as previously
described. Two parameters of morbidity were analysed to assess
differences according to surgical speciality: presence or absence of any
Adverse Event (AE) and the Soleymani and Collins Obstetric Morbidity
Score (SaCOMS). The first measure (AE) describes whether a woman with
PAS has experienced any adverse surgery-related outcome, regardless of
severity or multiple morbidities. Calculating SaCOMS allows a broader
perspective of the overall `patient journey', accounting for the
cumulative effect of multiple adverse complications both during and
beyond delivery.

\subsection*{}

{\label{section-1}}

\subsection*{Statistical Analysis}

{\label{statistical-analysis}}

The Shapiro-Wilk test for normality and Mann-Whitney U test were used to
assess for difference in age, BMI and gestation between surgeon groups.
Three parameters were tested to compare morbidity outcomes for
gynaecologist vs gynae-oncologist led MDTs. Chi-squared (\selectlanguage{greek}χ\selectlanguage{english}2) and
Fisher's exact tests, as appropriate, were used to compare the
proportion of women experiencing any measurable morbidity (AE) according
to the surgeon operating. The values for the SaCOMS were tested for
normality using the Shapiro-Wilk test and compared between surgeon
groups using the Mann-Whitney U test. For all tests \emph{p} \textless{}
0.05 was used as the threshold for statistical significance. All
statistical analysis was carried out using SPSS (SPSS 26.0; IBM
Analytics).

\section*{Results}

{\label{results}}

\subsection*{Validation of Modified Obstetric Clavien-Dindo and
SaCOMS}

{\label{validation-of-modified-obstetric-clavien-dindo-and-sacoms}}

10 completed responses to the Delphi consensus survey were recorded
(Table 4). Seven respondents were obstetricians, two were
gynae-oncologists and one was a specialist in maternal-fetal medicine.
For all quantifiable, Likert-scale items, the 80\% threshold for
approval was met. 100\% of respondents either `strongly agreed' or
`agreed' that there was a need for an obstetric-specific morbidity
classification system; 90\% felt that the Modified Obstetric
Clavien-Dindo fulfilled such a need, and 80\% felt that the generation
of a cumulative morbidity score (SaCOMS) value was useful. All
respondents reported that they would feel comfortable using the
classification system for the assessment of morbidity, with 80\%
reporting that they would feel comfortable using both the classification
and cumulative SaCOMS value. All respondents also reported they felt the
classification system was reasonable, fair and easy-to-apply, with 90\%
reporting they also felt this for SaCOMS.

\subsection*{}

{\label{section-2}}

\subsection*{Retrospective analysis of PAS
cohort}

{\label{retrospective-analysis-of-pas-cohort}}

Between August 2011 and May 2019, 83 possible PAS cases were identified
(Fig. 1). Seven cases (8\%) were excluded initially: four because they
were not delivered at the institution undertaking the audit; one because
the patient's notes could not be found; one because delivery was vaginal
followed by failed removal of placenta, and one case which was a false
positive PAS diagnosis (at delivery placentation was normal). Therefore,
76 cases were included in data collection; 8 (11\%) were `emergency' and
68 (89\%) were `elective'. Of the 68 electively delivered cases, 56
(82\%) were antenatally suspected PAS. Two of these cases (both
abnormally adherent i.e. FIGO Grade 1) were delivered by an MDT led by
an obstetrician and therefore excluded from the analysis. Of the
remaining 54 antenatally suspected, electively delivered PAS cases, 29
(54\%) were delivered by an MDT led by a gynae- oncologist and 25 (46\%)
were delivered by a gynaecologist-led MDT. There was no significant
difference in age (\emph{p}=0.77, \selectlanguage{greek}µ\selectlanguage{english}=27.5, SD=57.6) or gestation at
delivery (\emph{p}=0.21, \selectlanguage{greek}µ\selectlanguage{english}=27, SD=56.0), between the surgeon groups. BMI
was significantly higher in the gynae-oncology led cohort
(\emph{p}=0.01, \selectlanguage{greek}µ\selectlanguage{english}=27.5, SD=57.6). 19 (35\%) of the 54 cases were
classified as abnormally adherent (FIGO grade 1), and 35 (65\%) as
abnormally invasive (FIGO grades 2 and 3); 7 of the abnormally adherent
cases (37\%) were delivered by gynae-oncologists and 12 (63\%) were
delivered by gynaecologists. Of the 35 invasive cases, 22 (63\%) were
delivered by gynae-oncologists and 13 (37\%) were delivered by
gynaecologists (Fig. 1). A range of adverse outcomes were recorded
(Table 5) according to the Modified Obstetric Clavien-Dindo
classification. These included three cases where blood loss was
sufficient to necessitate a significant transfusion ([?]5 units packed red
cells) and one requiring massive blood transfusion ([?]10 units packed red
cells). Other surgical morbidities included 14 women requiring 15
returns to theatre without general anaesthetic, and 9 women with a total
of 17 additional procedures requiring general anaesthetic. Additional
procedures included two incidences of bladder damage (one conservatively
managed, one surgically managed at the time of caesarean), removal of
ureteric stents (8 without and 1 with general anaesthesia), and one
woman who required a nephrostomy following four unsuccessful attempts at
ureteric stenting. Two women went to ITU for acute respiratory distress
syndrome (ARDS), a single-organ failure. No women had multi-organ
failure. No women in this study met the criteria for either sepsis or
DIC, but six had post-operative infections leading to systemic
inflammatory response syndrome (SIRS). Overall, of the 54 elective,
antenatally suspected cases 24 experienced at least one adverse outcome
as a result of the surgery. The difference in incidence of at least one
adverse event between women delivered by gynae-oncological surgeons vs
gynaecological surgeons was significant {[}31\% (9/29) versus 60\%
(15/25), \emph{p}=0.033{]} (Table 6). When severity of PAS according to
the FIGO classification was accounted for, there was no significant
difference in the proportion of women experiencing at least one adverse
outcome between gynae-oncologists and gynaecologists for abnormally
adherent (FIGO Grade 1) cases {[}28.6\% (2/7) versus 41.7\% (5/12),
\emph{p}=0.656){]} (Table 6). However, for abnormally invasive (FIGO
Grade 2 or 3) cases significantly fewer women experienced at least one
adverse outcome when operated on by gynae- oncologists compared to those
operated on by gynaecologists {[}31.9\% (7/22) versus 76.9\% (10/13),
\emph{p}=0.01{]} (Table 6). Differences in SaCOMS were examined (Fig.
2). The Shapiro-Wilk test demonstrated that SaCOMS values were not
normally distributed (\emph{p}[?]0.001) for electively delivered,
antenatally suspected PAS cases. Therefore, the Mann-Whitney-U test was
used. SaCOMS was lower for women delivered by gynae-oncological surgeons
than for women delivered by gynaecological surgeons (Mean Rank of 23.7
versus Mean Rank of 31.9, U=252.5, \emph{p}=0.04) (Fig. 2a). For
abnormally adherent cases, SaCOMS did not differ significantly between
gynaecological surgeons and gynae-oncological surgeons (Mean Rank of
10.4 versus Mean Rank of 9.4, U=37.5, \emph{p}=0.71) (Fig. 2b). However,
for more severe cases (FIGO grades 2 and 3), women delivered by
gynaecological surgeons had significantly higher SaCOMS than women
delivered by gynae-oncological surgeons (Mean Rank of 23.5 versus Mean
Rank of 14.7, U=71.0,\emph{p}=0.01) (Fig. 2c).

\section*{Discussion}

{\label{discussion}}

\subsection*{Main findings}

{\label{main-findings}}

We propose adoption of a modified approach to the widely-used
Clavien-Dindo classification, adapted to reflect the portfolio of risks
associated with complex obstetric cases and extended to develop the
Soleymani and Collins Obstetric Morbidity Score (SaCOMS) - a novel
morbidity assessment tool which has the additional benefit of accounting
for the cumulative impact of multiple adverse outcomes on the overall
patient journey. We have validated this classification methodology by
Delphi consensus consultation of expert clinicians, and have
demonstrated its utility via consideration of two case studies and a
retrospective analysis of a cohort of patients with PAS.

\subsection*{Interpretation}

{\label{interpretation}}

Evaluation of two case studies indicates the additional patient-focused
insight this provides; the additive detriment of six follow-up
procedures despite a low-grade of clinical disease for patient 1
compared to well-managed blood loss and a one-night observative stay in
ICU for patient 2 (with a high-grade of clinical disease) is reflected
in a notably higher SaCOMS value. A survey-based modified Delphi
consensus shows that relevant clinicians believe this system to provide
value in assessing morbidity for individual patients and analysis of
data. In addition to qualitative consideration of the Modified Obstetric
Clavien-Dindo classification and SaCOMS by considering individual case
studies, its utility as a tool for quantitative analysis to draw
meaningful clinical conclusions is demonstrated by retrospective
analysis of morbidity outcomes for surgical delivery women with PAS by
type of surgeon leading the MDT. The major finding of the retrospective
PAS cohort analysis was that, according to both measures of morbidity -
presence of any adverse event, and SaCOMS - gynae-oncologist led MDTs
had significantly better outcomes than gynaecologist-led MDTs for
electively delivered, antenatally suspected PAS cases. These data
suggest that women delivered by gynae-oncological surgeons are less
likely to experience any measurable morbidity, irrespective of severity
or multiple morbidities. Furthermore, for women who experienced adverse
outcomes, delivery by gynae-oncological surgeon was associated with a
lower cumulative experience of morbidity. As both parameters of
morbidity concur this provides evidence that gynae- oncological surgeons
provided the safest management of PAS, particularly for clinically
severe cases, probably due to their extended training in open laparotomy
and experience with friable, hyper-vascularised tissue and distorted
anatomy20. Adequate clinical and academic assessment of maternal
morbidity from obstetric procedures has previously been hindered by a
lack of consensus in classification and reporting of adverse events. In
turn, this limits evidence-based evaluation of the benefit of novel
techniques and intervention for complex obstetric disorders, such as
PAS. Studies examining morbidity from complex obstetric cases tend to
put the emphasis on the amount of blood lost, blood products given and
admission to intensive care unit (ICU). Whilst these are undoubtedly
important markers, they are fraught with difficulties. Blood loss is
always an estimate and the blood products given are often dependent on
the practice of the anaesthetist and local guidelines. ICU admission may
also be impacted by the availability of ICU beds or presence of a
specific obstetric high dependency unit (HDU) as well as local practice
and guidelines. Other morbidities recorded often include accidental
visceral trauma or post-operative infection. Again, these can result in
significantly different experiences for the woman herself; a cystotomy
repaired at the time of surgery is likely to have a lower impact on her
quality of life than ureteric trauma requiring multiple surgical
interventions over the months or years to come. This is particularly
important as the patient is a new mother and any ongoing morbidity may
affect her ability to bond with, and care for, her new baby. This can
also have significant impacts on her partner and other children.

\subsection*{Strengths and Limitations}

{\label{strengths-and-limitations}}

A cohesive and consistent system for classifying surgical morbidity in
obstetrics which is reflective of the burden of cumulative morbidity
events, has the potential to improve the accuracy and utility of
academic research into surgical morbidity in obstetrics. Clinically,
this has the knock-on effect of bolstering efforts to develop and
optimising the surgical approach to complex obstetric surgery, guided by
enhanced research methodology. A potential confounding factor could be
clinical severity of PAS for the cases managed by each surgeon type. For
example, if gynae-oncologists had been undertaking most of the less
invasive, less clinically severe cases (and/or gynaecologists undertook
disproportionately more high-grade cases) this could obfuscate any true
relationship between surgeon type and morbidity outcomes. Sub-group
analysis by severity demonstrated that this was not the case;
gynaecologists performed most of the deliveries for abnormally adherent
(FIGO Grade 1) cases (12/19, 63\%), and gynae- oncologists performed the
majority of caesareans for the more technically challenging abnormally
invasive (FIGO Grade 2 or 3) cases (22/35, 63\%). Furthermore, gynae-
oncology-led MDTs had better morbidity outcomes despite the women having
higher BMI scores, which increases surgical risk21--23. The difference
in morbidity outcomes between the two surgeon types varied between
abnormally adherent (FIGO Grade 1) and abnormally invasive (FIGO Grade 2
and 3) cohorts. Analysing the less surgically complex abnormally
adherent cases separately demonstrated that there was no significant
difference in incidence of any adverse event and SaCOMS between the
surgeon types for clinically less severe cases. For abnormally invasive
cases however, both morbidity parameters were significantly lower when
the MDT was led by gynae-oncological surgeons. This suggests that
gynae-oncological surgeons are better equipped to tackle the surgical
complexity required to manage more severe, invasive cases of PAS (which
inherently carry a higher surgical risk18). Surgical experience is
another potential confounding factor to consider; if gynae- oncologists
performed more PAS surgeries overall, this could allow for increased
experience of MDTs and of individual surgeons. Surgical experience is
well correlated with improved surgical outcomes for several types of
surgery24--26 (known as the volume-outcome relationship), including in
the management of PAS27. This was not the case however, as both surgeon
types performed a similar number of surgeries in the study period.
Gynaecologists performed caesarean hysterectomies for 46.3\% (25) of all
elective antenatally suspected PAS cases within the study period, whilst
gynae-oncologists performed the remaining 53.7\% (29). Although the
learning curve of individual surgeons and MDTs cannot be controlled for,
the specialist PAS service at the JRH was led by gynaecologists for four
years (2011-2014) and by gynae-oncologists for four and a half years
(2015-mid 2019), allowing for a similar timeframe to develop familiarity
with operating on women with PAS. An important strength of the morbidity
analysis is the robustness of the diagnostic criteria for PAS. All cases
included were confirmed by experts in PAS diagnosis according to strict
clinical criteria and histopathological diagnosis. This enabled the
sub-division into the less severe abnormally adherent and more
surgically complex abnormally invasive cases. A notable limitation to
the retrospective morbidity analysis is the small sample size, with data
from only one NHS trust. It would be difficult to scale-up this study to
include multiple NHS trusts, owing to the highly specialist nature of
the surgery requiring referral to specialist tertiary-level obstetric
units28. PAS is a very rare placental disorder, with an estimated
incidence of 0.07\% (IQR 0.05-0.16)29, meaning the sample size was
unavoidably very small and the study had low power to detect mild to
moderate effects. However, statistical significance across both measures
of morbidity is testament to the effect size of using gynae-oncological
surgeons. A prospective study or rolling audit over a period of several
years might reveal additional statistically significant results and rule
out type II statistical errors. For example, a difference in morbidity
outcomes between gynae-oncologists and gynaecologists for abnormally
adherent cases might be revealed with higher-powered analysis afforded
by a greater sample size. It would also allow accurate data collection
at the time of surgery, according to a pre-defined pro forma and
tailored to the research aims. This could facilitate investigation of
additional morbidities for which there was not sufficient data available
for the present study; for example psychological sequelae such as PTSD,
which has been associated with PAS30. A larger cohort would also allow
investigation of morbidity outcomes in emergency cases, for which the
sample size was too small to analyse in the present study.

\subsection*{Conclusion}

{\label{conclusion}}

Clinicians with expertise in PAS believe that the Modified Obstetric
Clavien-Dindo classification system and the novel SaCOMS tool can aid in
drawing meaningful clinical conclusions regarding maternal morbidity,
including representing the detrimental impact of cumulative morbidity
outcomes. Analysis of two morbidity parameters including the novel
SaCOMS, demonstrated that for women electively delivered with
antenatally suspected PAS, surgery by gynae-oncological surgeons was
associated with better morbidity outcomes compared to delivery by
gynaecological surgeons, especially for more clinically severe cases.
This is probably due to greater experience with handling the distorted
anatomy, neovascularity and friable tissue encountered with abnormal
placentation. These data suggest a potential benefit to using
gynae-oncology-led MDTs as standard for PAS caesarean
deliveries.\textbf{Conflicts of Interests:} The authors have nothing to
disclose.\textbf{Contribution to Authorship:} EW: methods, data
collection, data analysis, manuscript preparation and approval. SC/HS:
Concept, methods, data analysis, manuscript preparation and approval.
SA/AC: Methods, data analysis, manuscript preparation and
approval.\textbf{Ethical Approval:} The data was collected as part of a
locally approved audit (OUH Audit 5544).\textbf{References}1. Bartels,
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