Baseline, disease
and management characteristics
A cohort of 797 patients was recruited in PAS-ID. Of those, 727 women
were considered eligible for this current study based on adequate
documentation of patient outcomes. Mean age of participants was 33.15 ±
4.93 years, mean parity was 2.20 ± 1.37, and mean BMI was 27.89 ± 4.50
kg/m2. Prevalence of twin pregnancy was 2.6%.
Pregnancy was complicated by gestational diabetes and hypertension in
8.6% and 7.1%, respectively. Participants reported history of
obstetric dilation and curettage (D & C) in 26.92% and history of
gynaecologic D & C in 14.96% of cases. The placenta was most commonly
located centrally over the internal os (35.76%). Mean antepartum
hemoglobin level was 11.04 ± 1.43 g/dl. Preoperative ultrasound was
performed in 95.32% of cases and 4.13% underwent intraoperative
ultrasound. Planned cesarean hysterectomy was performed in 18.7% of
patients.
Placenta accreta was encountered in 41.68%, followed by placenta
increta (31.22%) and percreta (27.10%). Bladder invasion was present
in 13.07% of cases. The most commonly performed uterine incision was
low transverse (56.03%), followed by high transverse incision
(27.88%). Delayed cord clamping was done in 16.69% of all deliveries.
Incising through the placenta to deliver the fetus occurred in 28.75%
of cases. Among women who were conservatively managed, the most commonly
performed procedure was compression sutures (32.88%). Different
modalities of IR were used in 9.42% of cases. Incidence of
unintentional cystotomy was 10.18%. Patient characteristics, PAS
characteristic and management details are summarized in Table 1.
Primary and secondary outcomes
Massive PAS-associated blood loss was reported in 17.74% of all cases.
Mean estimated blood loss was 1786.33 ±1707.74 ml. Patients received a
mean of 2.66 ± 4.91 of packed RBCs units, 1.37 ± 2.69 of fresh frozen
plasma units, 1.42 ± 6.37 of cryoprecipitate and 0.81 ± 4.45 of platelet
unites. Peripartum DIC manifested in 5.78% of patients. After delivery,
26% of all patients were admitted to the ICU. Mean length of hospital
admission was 6.16 ± 6.36 days. Mean postoperative hemoglobin was 9.33 ±
1.75 g/dl (Table 1).
Prediction model using conventional statistics
Among prenatally-determined variables, maternal age (aOR 1.06; 95% CI,
1.001 – 1.12), ethnicity (aOR 0.09; 95% CI, 0.04 – 0.23), previous CS
(aOR 5.65; 95% CI, 1.91 – 16.73 for previous 2 CSs), prior
gynaecologic D & C (aOR 2.83, 95% CI, 1.37 – 5.80), antepartum
hemoglobin level (aOR 0.75; 95% CI, 0.62 – 0.90), and intrauterine
fetal death (aOR 6.40; 95% CI, 1.04 – 39.48) were significantly
associated with risk of massive blood loss. AUC of antepartum model
performance was 0.84 and 0.81 among development and validation groups,
respectively (Table S1).
Adding peripartum variables to the model, variables that exhibited
significant association with massive blood loss included ethnicity (aOR
0.18; 95% CI, 0.05 – 0.67), Previous 2 CS (aOR 4.92; 95% CI, 1.34 –
18.05), prior gynaecologic D & C (aOR 4.58; 95% CI, 1.76 – 11.93),
intrauterine fetal death (aOR 18.36; 95% CI, 1.68 – 200.73) and
preoperative hemoglobin (aOR 0.75; 95% CI, 0.61 – 0.93). Significant
intraoperative variables were placental bed sewing (aOR 0.17; 95% CI,
0.04 – 0.70), incising through the placenta (aOR 0.31, 95% CI, 0.14 –
0.69), IR (aOR 3.48; 95% CI, 1.23 – 9.78), complete placental invasion
(aOR 3.92; 95% CI, 1.71 - 8.99), and bladder invasion (aOR 5.33; 95%
CI, 2.27 – 12.50). AUC for this model was 0.91 for development group
and 0.82 for validation group (Table S1).
ML prediction modelsAntepartum prediction model (MOGGE PAR-A score)For PAS-associated massive blood loss, diagnostic accuracy of antepartum
ML model was 0.84 for both train and test sets (Figure 1A). Model
evaluation is summarized in Table 2. The most contributing factors to
this model were parity (12%), previous CSs (12%), Asian ethnicity
(12%), and centrally located placenta (9%). Size of contribution of
baseline variables in this model is illustrated in Figure 2A. Median and
interquartile range (IQR) of calculated probability was 13.0 (9.0 –
19.1) in women who did not have massive blood loss and 22.5 (16.3 –
32.5) in women with massive blood loss (Figure 3A).
Antepartum ML model for prediction of prolonged hospitalization was
associated with an AUC of 0.80 and 0.81 for train and test sets,
respectively (Figure 1B). Asian ethnicity was the most influential
variable to this model (14%), followed by central placenta (12%),
anterior low placenta (10%), antepartum diagnosis using abdominal
sonography and Doppler assessment (9%), and antepartum hemoglobin level
(8%) (Figure 2B). Women who were hospitalized for > 7 days
had a median probability of 12.1 (8.6 – 18.6) compared to women who
were hospitalized for a shorter duration (7.1 [4.9 - 10.0]) (Figure
3B).
Diagnostic accuracy of antepartum
ML prediction of maternal ICU admission was 0.85 (train set) and 0.82
(test set) (Figure 1C). Major contributors to the model include European
and Asian races (15% and 13%, respectively), central placenta (12%),
posterior and anterior low placentas (7%), parity (5%), BMI ≥ 30
(5%), previous CSs (5%), antepartum hemoglobin (5%) (Figure 2C).
Women who were and were not admitted to ICU had a median probability of
27.6 (17.9 – 39.8) and 11.3 (7.1 – 17.6), respectively (Figure 3C).Peripartum prediction model (MOGGE PAR-P score) Peripartum prediction model of massive blood loss yielded an AUC of 0.88
and 0.86 for train and test tests, respectively (Figure 1D). Method of
diagnosis of PAS presented a major contribution to this model, including
whether ultrasound was combined with Doppler assessment (12%) or
magnetic resonance imaging (MRI) (10%), or if diagnosis was first made
intrapartum (7%). Other major variables are parametrial invasion (8%),
and bladder invasion (5%) (Figure 2D). Median calculated probability
among women who had massive blood loss was 27.4 (17.8 – 39.8) and 12.8
(9.4 – 18.3) in women with no massive bleeding (Figure 3D).
Regarding prolonged hospitalization, AUC of peripartum model was 0.86
for the train and 0.90 for the test set (Figure 1E). Parametrial
invasion contributed the most to this model (12%), followed by high
transverse uterine incision (8%), intraoperative ultrasound (7%),
bladder invasion (6%) (Figure 2E). Median probability in women who were
admitted for longer than 7 days was 10.5 (7.4 – 16.4), while women who
were admitted for shorter duration had a median of 6.3 (4.8 – 8.6)
(Figure 3E).
AUC peripartum prediction model of ICU admission was 0.88 and 0.86 for
the train and test sets, respectively. The largest contribution comes
from ethnicity (Asian [17%] and European [9%]), delayed cord
clamping (7%), complete placental invasion (4%), and internal iliac
artery ligation (4%) (Figure 2F). Calculated probability of admission
to ICU in women who were or were not admitted to ICU was 11.4 (5.2 –
21.5) and 1.6 (0.5 – 5.2), respectively (Figure 3F).