Comparison of perioperative outcomes and anesthetic-related complications of morbidly obese and super-obese parturients delivering by cesarean section

Abstract

Objective

To compare the perioperative outcomes and anesthetic-related complications of morbidly obese and super-obese parturients delivering by cesarean section.

Methods

A retrospective analysis of 6 years of data was performed. Exclusions were cases with gestational ages <24 weeks, placenta accreta spectrum, polyhydramnios, or multiple gestations.

Results

The study included 494 patients whose body mass index (BMI) exceeded 40 kg/m² at delivery. Of these, 469 were morbidly obese (BMI 40–49.9; mean, 42.9 ± 2.4), and 25 were super obese (BMI >50; mean, 54.5 ± 4.2). Twenty-four (5.1%) morbidly obese women received general anesthesia. The other 445 patients (94.9%) in the morbid obesity group underwent cesarean delivery under regional anesthesia; however, some (2.2%; 10/445) received general anesthesia after regional anesthesia failed. In the super-obesity group, 23 patients (92.0%) received regional anesthesia, while two patients (8.0%) received general anesthesia. There were no cases of pulmonary aspiration, maternal deaths, or difficult or failed intubation. There was one episode of cardiac arrest in a patient with a BMI of 47.9. Among the morbidly obese and super-obese women given regional anesthesia, the super-obese patients had significantly greater volumes of ephedrine and norepinephrine consumption (p = 0.027 and 0.030), intravenous fluids (p = 0.006), and bleeding during surgery (p = 0.017). They also had more hypotensive episodes (p = 0.038). The two groups’ incidences of neonatal birth asphyxia, postpartum hemorrhage, blood transfusion, and uterine atony did not differ significantly. The lengths of stay in the hospital were also comparable.

Conclusions

Among the women receiving regional anesthesia, the super-obese parturients had greater intraoperative bleeding, a higher proportion of hypotensive episodes, and a greater vasopressor requirement than the morbidly obese parturients. Anesthesiologists must prepare for the adverse perioperative events that such women risk experiencing during a delivery by cesarean section.

Trial registration

www.clinicaltrials.gov ID: NCT04657692.

KEY MESSAGES

• Super obesity parturients are at a significantly higher risk of intraoperative bleeding, maternal hypotension, and higher vasopressor requirement compared to parturients with morbid obesity undergoing cesarean delivery.

• We additionally found a weak positive correlation between patient body weight and intraoperative blood loss in a patient with morbid obesity regardless of anesthetic technique.

Keywords:

• Anesthesia
• cesarean delivery
• complications
• morbid obesity
• perioperative outcomes
• super obesity

Introduction

There is a growing epidemic of obesity in the general population. The global prevalence of morbid obesity in women is estimated at 1.6% [1], and adult obesity has been projected to continually increase in some countries, such as the United States [2]. The level of obesity among women in the United States who are of childbearing age (20–39 years) was recently reported to be high (39.7%), according to an analysis drawing upon the National Health and Nutrition Examination Survey [3]. Consequently, the proportion of parturients with obesity is increasing. It is generally nown that obesity is related to an increased risk of comorbidities, such as obstructive sleep apnea, type 2 diabetes, systemic hypertension, fatty liver disease, and coronary arterial disease [4]. Pregnant women with obesity also have an increased risk of maternal and neonatal complications [5]. The obstetric-related adverse outcomes in the perinatal period include preeclampsia, diabetes, postpartum hemorrhage, postpartum infection, macrosomia, preterm birth, and neonatal morbidity and mortality [5–10]. A meta-analysis revealed that the rate of cesarean delivery in individuals who were overweight or obese increased in line with their body mass: a higher body mass index (BMI) led to a higher chance of cesarean delivery [11].

A previous comparison of anesthetic complications in patients without obesity and those who are morbidly obese revealed that morbid obesity increased the risks of difficult tracheal intubation, failed analgesia for labor, and high spinal block [12–14]. Given the complexities of anesthetic management, there is little data on the effects of weight on the anesthetic complications of patients who are morbidly obese or super obese. Moreover, there is no universal consensus on the BMI cutpoints that should define these two levels of obesity in parturients. Because our study focused on the perioperative period, we used patients’ BMIs at delivery. A BMI of 40 kg/m² was classified as ‘morbid obesity’, while a BMI of ≥50 kg/m² was classified as ‘super obesity’.

The primary objective of this retrospective study was to identify and compare the anesthesia-related complications of parturients with morbid obesity and super obesity. The secondary aim was to compare the adverse obstetrics and neonatal outcomes of patients who are morbidly obese or super obese during the perioperative period.

Methods

Study design and study population

This retrospective cohort study was conducted at Siriraj Hospital, Mahidol University, Bangkok, the largest university hospital in Thailand. The Siriraj Institutional Review Board approved the study (protocol number 873/2562[IRB2]; approval number Si125/2020; approved 13 February 2020). As this was a retrospective chart review, informed consent was not needed. The study was registered with www.clinicaltrials.gov (NCT04657692).

We included parturients with a BMI ≥40 kg/m² undergoing cesarean delivery between 1 January 2014 and 31 December 2019. The exclusion criteria were a gestational age <24 weeks, fetal death in utero, placenta accreta spectrum, polyhydramnios, and multiple gestations. The hospital numbers of patients were retrieved from the anesthetic department database. Detailed obstetrical and anesthetic data of eligible patients were then collected from our hospital’s medical record center, which stored records in electronic files. Patients were withdrawn from the study if data were incomplete or missing. We recruited 494 consecutive patients with morbid obesity or super obesity who underwent cesarean delivery. Patients were stratified into two groups: a morbid obesity group (BMI 40–49.9 kg/m²) and a super obesity group (BMI ≥50 kg/m²). The primary outcome was anesthetic complications occurring during the perioperative period (from the operation day to hospital discharge).

Sample size

The estimation of the number of subjects required for this study was based on the findings of previous studies. They revealed that the anesthesia complications related to cesarean delivery in patients with obesity were difficult intubation (35.3%) [12], failed regional analgesia (17%) [13], high spinal block (0.31–2.53%) [14], and blood transfusion (1.7–3.2%) [15]. Therefore, we used an incidence of 2% for our calculation. With an α value of 0.05, a confidence level (1 − α) of 95%, and an allowable error of 0.015, a two-sided test determined that at least 335 patients were required. We included an additional patient number of 10%; thus, this study’s total number of patients needed to exceed 369.

Data analysis

Statistical analyses were performed on PASW Statistics for Windows, version 18.0 (SPSS Inc., Chicago, IL, USA). The demographic and obstetric characteristics are reported as mean, standard deviation (SD), number (percentage), and minimum and maximum. Dichotomous variables were analyzed with the Chi² test or Fisher’s exact test. Continuous data were compared using the independent t-test or the Mann–Whitney U test. Spearman’s correlation coefficient was used to describe the relationship between body weight and intraoperative blood loss. Probability (p) values <0.05 were considered statistically significant.

Definitions

‘Difficult intubation’ was defined as three or more attempts at intubation. ‘Desaturation’ was defined as maternal oxygen saturation of <90% recorded for ≥5 min. ‘Hypotension’ was defined as systolic blood pressure (SBP) <20% of the SBP before the induction of anesthesia or use of a vasopressor agent. Episodes of hypotension were retrieved from the anesthetic records or counted by the number of boluses of any vasopressor. ‘Bradycardia’ was defined as a heart rate <50 beats per minute or when atropine was administered. ‘Postpartum hemorrhage’ was defined according to the American College of Obstetricians and Gynecologists criteria: bleeding exceeding 1,000 ml after delivery [16]. The intraoperative blood loss was determined by visual estimation by the attending anesthesiologist in the operating theatre. All patients received a uterotonic agent (intravenous oxytocin or carbetocin) after delivery; ‘uterine atony’ was defined as the need to use an additional agent (e.g. methylergonovine or prostaglandin). ‘Failure of regional anesthesia’ was defined as the need to convert to general anesthesia with an endotracheal tube. ‘Neonatal birth asphyxia’ was defined as a neonatal Apgar score <7 five minutes after delivery.

Results

Demographics of participants

In the 6-year study period (2014–2019), there were 22,191 cesarean deliveries at our center. On the delivery day, 527 patients had a BMI ≥ 40 kg/m². After applying the exclusion criteria, 33 patients were excluded, leaving 494 patients for analysis (Figure 1). A total of 257/494 patients (52%) received emergency cesarean section, while 237/494 patients (48%) underwent elective surgery. Table 1 compares the group’s demographic and clinical characteristics as well as their choices of anesthesia.

Figure 1. Flow chart of study population. BMI: body mass index; GA: general anesthesia; RA: regional anesthesia; SB: spinal block; EB: epidural block; CSE: combined spinal epidural block.

Table 1. Demographic data, clinical characteristics, and choice of anesthesia (N = 494).

Parameters	Value	BMI 40–49.9 kg/m^2 (n = 469)	BMI ≥ 50 kg/m^2 (n = 25)	p-Value
Age (years)	30.0 ± 5.6 (18–45)	30.1 ± 5.6 (18–45)	29.16 ± 5.9 (19–39)	0.421
Weight (kg)	110.9 ± 12.9 (85.7–180.0)	109.5 ± 10.8 (85.7–151.7)	138.42 ± 17.62 (109.0–180.0)	<0.001*
Height (cm)	159.5 ± 6.2 (145.0–178)	159.5 ± 6.2 (145.0–178)	159.1 ± 6.7 (147.0–175.0)	0.772
Body mass index (kg per square meter)	43.6 ± 3.6 (40–65.1)	42.9 ± 2.4 (40–49.9)	54.5 ± 4.2 (50.1–65.1)	<0.001*
Primigravidarum	172 (34.8)	162 (34.5)	10 (40.0)	0.577
Gestational age (weeks)	37.8 ± 1.7 (28–42)	37.9 ± 1.7 (28–42)	37.7 ± 1.8 (31–40)	0.717
ASA physical status classification
II	355 (71.9)	345 (73.6)	10 (40.0)	<0.001*
III	135 (27.3)	121 (25.8)	14 (56.0)
IV	4 (0.8)	3 (0.6)	1 (4.0)
Emergency	257 (52.0)	243 (51.8)	14 (56.0)	0.683
Underlying disease^a
Hypertension	133 (26.9)	120 (25.6)	13 (52.0)	0.04*
Diabetes mellitus type 2	43 (8.7)	42 (9.0)	1 (4.0)	0.713
Thalassemia trait and disease	116 (23.5)	112 (23.9)	4 (16.0)	0.365
Asthma	13 (2.6)	13 (2.8)	0 (0)	1.000
Pregnancy-associated problems
Gestational hypertension	48 (9.7)	47 (10.0)	1 (4.0)	0.496
Gestational diabetes	101 (20.4)	95 (20.3)	6 (24.0)	0.651
Preeclampsia	106 (21.5)	100 (21.3)	6 (24.0)	0.751
Indication for cesarean delivery^b
Previous cesarean delivery	207 (41.9)	197 (42.0)	10 (40.0)	0.843
Cephalopelvic disproportion	137 (27.7)	129 (27.5)	8 (32.0)	0.625
Maternal preference for cesarean delivery	21 (4.2)	20 (4.3)	1 (4.0)	1.000
Code blue cesarean delivery	3 (0.6)	3 (0.6)	0 (0)	1.000
Choice of anesthesia (n = 26)
General anesthesia	26 (5.3)	24 (5.1)	2 (8.0)	0.384
Regional anesthesia (n = 458)
Single-shot spinal anesthesia	452 (91.5)	432 (92.1)	20 (80.0)	0.001*
Epidural anesthesia	2 (0.4)	2 (0.4)	0 (0)
Combined spinal and epidural anesthesia	4 (0.8)	1 (0.2)	3 (12.0)
Failed RA converted to GA (n = 10)	10 (2.0)	10 (2.1)	0 (0)	1.000

ASA: American Society of Anesthesiologists; BMI: body mass index; GA: general anesthesia; RA: regional anesthesia.

Data presented as mean ± standard deviation (minimum–maximum value) or number(percentage). * P < 0.05 indicates statistical significance.

^aOther underlying diseases included dyslipidemia, hyperthyroidism, chronic kidney disease, idiopathic thrombocytopenic purpura, systemic lupus erythematosus, history of stroke, amphetamine use, antiphospholipid syndrome, aplastic anemia, human immunodeficiency virus (HIV) infection, arrhythmia.

^bOther indications for cesarean delivery included abnormal fetal position, prolonged premature rupture of membrane, oligohydramnios, fetal macrosomia, non-reassuring fetal status, condyloma accuminata, fetal omphalocele, maternal heart diseases (atrial fibrillation with Wolff–Parkinson–White syndrome, diastolic heart failure), maternal HIV infection, previous myomectomy, chorioamnionitis, intrauterine growth retardation.

Clinical data of patients receiving general anesthesia

There were 26/494 (5.3%) patients who received general anesthesia; 24/26 patients had morbid obesity, whereas 2/26 patients had super obesity. There were no significant differences in the amount of intravenous (IV) crystalloid fluid administration, intraoperative blood loss, or the number of patients with uterine atony. No blood transfusions were performed in patients who received general anesthesia (Table 2). The incidences of neonatal birth asphyxia, the mean anesthetic induction durations, and the operating times of the morbid obesity and super obesity groups did not differ. Indications for general anesthesia included thrombocytopenia from idiopathic thrombocytopenic purpura, non-reassuring fetal status, code blue cesarean delivery, as well as other indications not specified in patients’ medical records.

Table 2. Intraoperative data of patients receiving general anesthesia (n = 26).

Parameters	BMI 40–49.9 kg/m^2 (n = 24)	BMI ≥ 50 kg/m^2 (n = 2)	p-Value
Desaturation with bronchospasm	1 (4.1)	0 (0.0)	1.000
Total intravenous fluid (ml)	1,117.9 ± 542.2	875.0 ± 388.9	0.544
Estimated blood loss (ml)	675.0 ± 438.4	575.0 ± 176.8	0.755
Uterine atony	10 (41.7)	0 (0)	0.508
Blood transfusion	0 (0)	0 (0)	N/A
Neonatal Apgar score–1 min	6.4 ± 1.8	8.0 ± 0.0	<0.001*
Neonatal Apgar score–5 min	8.9 ± 0.9	8.5 ± 0.7	0.573
Neonatal birth asphyxia	1 (0.2)	0 (0)	1.000
Anesthetic induction duration (min)	25.4 ± 20.1	30.5 ± 13.4	0.740
Operative duration (min)	68.7 ± 27.8	61.5 ± 9.2	0.722

Data presented as mean ± standard deviation or number (percentage). * P < 0.05 indicates statistical significance.

BMI: body mass index; min: minute; ml: millilitre.

One patient (BMI 47.9 kg/m²) suffered cardiac arrest in the operating theatre 5 minutes after delivery; it resulted from a massive pulmonary embolism. She received 15 minutes of cardiopulmonary resuscitation before the return of spontaneous circulation. Another patient (BMI 47.1 kg/m²) was diagnosed with severe preeclampsia with pulmonary edema; she remained intubated until the post-operative period. Post-operatively, both patients were admitted to the surgical intensive care unit (ICU). No cases of maternal mortality were reported.

Patients receiving regional anesthesia

Among the 445 patients with morbid obesity who received regional anesthesia, 10 (2.2%) had failed regional anesthesia, requiring conversion to general anesthesia. Patients with failed regional anesthesia and conversion to general anesthesia were withdrawn from the analysis. There was no difference in the number of patients in the groups who required emergency cesarean delivery. The most common complication after regional anesthesia was maternal hypotension, which accounted for 93.6 and 95.7% of complications in the morbid obesity and super obesity groups, respectively. The estimated intraoperative blood loss, amount of IV crystalloid fluid administered, and episodes of hypotension were higher for the super obesity group. Similarly, the quantity of ephedrine or norepinephrine used was significantly higher for the super obesity group (Table 3). None of the patients recorded inadequate respiration requiring endotracheal intubation from a high block or a block height above the first thoracic dermatomal level (T1). The skin-incision-to-delivery time, anesthetic duration, and operating duration were also longer for the super obesity group (Table 4).

Table 3. Intraoperative data of patients receiving regional anesthesia (n = 458).

Parameters	BMI 40–49.9 kg/m^2(n = 435)	BMI ≥ 50 kg/m^2(n = 23)	p-Value
Emergency cesarean delivery	220 (50.6)	13 (56.5)	0.578
Hypotension	407 (93.6)	22 (95.7)	1.000
Episodes of hypotension (n = 429)	7.3 ± 5.2 6 (3, 11)	9.6 ± 5.1 10 (4, 15)	0.038* 0.024*
Number of patients receiving any vasopressor	368/435 (84.6)	19/23 (82.6)	0.768
Total ephedrine usage (mg)	21.4 ± 15.1	30.4 ± 18.9	0.027*
Total norepinephrine usage (mcg)	20.9 ± 23.5	34.0 ± 19.1	0.030*
Number of patients receiving supplemental analgesic intraoperatively^a	71 (16.3)	2 (8.7)	0.557
Bradycardia	6 (1.4)	0 (0.0)	1.000
Spinal dosage 0.5% hyperbaric bupivacaine (ml)	2.2 ± 0.2	2.2 ± 1.5	0.758
Dermatomal blockade level (thoracic)	4.5 ± 1.4	4.9 ± 2.2	0.380
Level of blockade higher than T4	13 (3.0)	0 (0.0)	1.000
Total intravenous fluid (ml)	1201.9 ± 481.8	1,490 ± 592.1	0.006*
Estimated blood loss (ml)	455.0 ± 258.2 400 (150–3500)	589.1 ± 326.5 500 (250–1500)	0.017* 0.020*
Postpartum hemorrhage	18 (4.1)	2 (8.7)	0.265
Urine output (ml)	189.1 ± 129.8	236.1 ± 201.6	0.102
Blood transfusion	5 (1.1)	0 (0)	1.000

BMI: body mass index; mcg: microgram; mg: milligram; ml: milliliter; T4: the 4th thoracic dermatomal level.

Data presented as mean ± standard deviation, median (minimum-maximum value) or number (percentage). * P < 0.05 indicates statistical significance.

^aSupplemental analgesia included intravenous fentanyl, ketamine, and pethidine.

Table 4. Neonatal data–regional anesthesia (n = 458).

Parameters	BMI 40–49.9 kg/m^2(n = 435)	BMI ≥ 50 kg/m^2(n = 23)	p-Value
Neonatal birth weight (gram)	3307.3 ± 590.2	3373 ± 753.9	0.603
Skin incision to delivery time (min)	12.4 ± 6.7	16.9 ± 8.1	0.002*
Uterine incision to delivery time (min)	2.2 ± 1.4	2.1 ± 1.3	0.728
Apgar score–1 min	8.1 ± 1.2	8.4 ± 0.5	0.395
Apgar score–5 min	9.4 ± 0.8	9.5 ± 0.5	0.643
Birth asphyxia	4 (0.9)	0 (0)	1.000
Anesthesia induction duration (min)	21.22 ± 10.1	25.6 ± 11.1	0.043*
Operation duration (min)	61.5 ± 20.4	71.0 ± 25.4	0.032*

BMI: body mass index; min: minute; SD: standard deviation.

Data presented as mean ± standard deviation,  or number (percentage). * P < 0.05 indicates statistical significance.

Perioperative maternal and neonatal complications

Details of the perioperative complications of all patients, irrespective of the anesthetic technique used, are listed in Table 5. The morbid obesity and super obesity groups had no significant differences in their rates of postpartum hemorrhage, uterine atony, intrauterine balloon insertion, neonatal birth asphyxia, or injury to internal organs. No patients underwent peripartum hysterectomy or reoperation. Injury to internal organs occurred in five patients in the morbid obesity group (two patients: injury to the lower uterine segment; two patients: injury to the uterine artery; and one patient: tearing of the right broad ligament). A trivial positive correlation between maternal body weight and intraoperative blood loss was found, with a Spearman correlation coefficient of 0.146 (p < 0.001; Figure 2). A comparison of the mean intraoperative blood losses of the morbid obesity and super obesity groups is illustrated in Figure 3.

Figure 2. Correlation of maternal body weight and estimated blood loss (n = 494). Spearman correlation coefficient 0.146 (p < 0.001).

Figure 3. Comparing of intraoperative blood loss between morbid obesity and super-morbid obesity (n = 494). Graph represented in mean ± 1SD; p-value = 0.039.

Table 5. Perioperative data regardless of anesthetic technique (n = 494).

Perioperative data	BMI 40–49.9 kg/m^2(n = 469)	BMI ≥ 50 kg/m^2(n = 25)	p-Value
Number of patients requiring additional analgesic medication in recovery room	63 (13.5)	2 (8.0)	0.759
Number of patients requiring antiemetics in recovery room	2 (0.4)	0 (0)	1.000
Intraoperative blood loss	470.5 ± 274.3 400 (150–3500)	588.0 ± 314.7 500 (250–1500)	0.039* 0.021*
Postpartum hemorrhage	24 (5.1)	2 (8.0)	0.384
Uterine atony	119 (25.4)	4 (16.0)	0.291
Birth asphyxia	5 (1.1)	0 (0)	1.000
ICU admission	2 (0.4)	0 (0)	1.000
Intrauterine balloon	1 (0.2)	0 (0)	1.000
Injury of internal organ	5 (1.1)	0 (0)	1.000
Hospital length of stay (days)	5.2 ± 3.8 5 (3–74)	4.9 ± 1.2 5 (3–8)	0.732 0.731

BMI: body mass index; ICU: intensive care unit; SD: standard deviation.

Data presented as mean ± standard deviation, median (minimum-maximum value), or number (percentage). * P < 0.05 indicates statistical significance.

Three patients in the morbid obesity group developed post-dural puncture headache, and two of the three patients subsequently received epidural blood patches. One patient in the morbid obesity group suffered a surgical wound infection requiring IV antibiotics on the third post-operative day. The other post-operative complications reported were lung atelectasis, ilioinguinal neuralgia, endometritis, bleeding from external hemorrhoids, and urinary tract infection. The hospital lengths of stay of the two groups of patients showed a non-significant difference.

Discussion

We have described the anesthetic complications and perioperative maternal and neonatal outcomes of parturients undergoing cesarean delivery who were morbidly obese or super obese. Our analysis found that intraoperative hypotension was the most common complication in regional anesthesia patients. In patients with hypotension, a higher number of hypotensive episodes and a greater quantity of vasopressors were found in the super obesity group. The volume of intraoperative bleeding and IV fluid administration were significantly higher for the parturients who were super obese than those with morbid obesity.

Reports during the last decade have described a high prevalence of overweight adults in Thailand [17]. However, only a tiny proportion of the parturients who had a cesarean delivery at our institute were morbidly obese (BMI ≥ 40 kg/m²): 2.2% (∼500 patients in 22,191 cesarean deliveries). In contrast, data from the United States showed a high prevalence of mothers with morbid obesity (12–25%) [15,18]. However, our prevalence was consistent with the rates reported for the United Kingdom by the Centre for Maternal and Child Enquiries in 2010. It stated that 2.01% of pregnant women had a BMI ≥ 40 kg/m², and 0.19% had a BMI ≥ 50 kg/m² [19].

The unfamiliarity of providing anesthesia to parturients at our institute who are super obese may result in a high rate of complications. Unsurprisingly, the anesthesia ready time (the time taken by the anesthetist to provide sufficient anesthetic depth for the surgery to start) was significantly longer for patients with super obesity. Difficulty performing regional anesthesia and analgesia for parturients with obesity has been previously reported, with a higher BMI signifying an increased chance of difficulty and failure [20,21].

The present study showed that a larger amount of intraoperative bleeding was associated with a higher BMI. Earlier research on a large population in Sweden reported a higher risk of atonic postpartum hemorrhage in parturients with obesity after normal and instrumental deliveries than in parturients with normal weight [22]. A study from New Zealand demonstrated that being obese was a risk factor for major postpartum hemorrhage (bleeding ≥ 1,000 ml) after cesarean and vaginal deliveries [7]. A similar trend has been found in postpartum hemorrhage patients undergoing vaginal and cesarean deliveries. Specifically, the parturients with obesity (BMI ≥ 30 kg/m²) had significantly higher blood loss than those with a normal BMI [23]. In the case of the current investigation, the parturients with super obesity had higher blood losses. The greater losses occurred despite the morbid obesity and super obesity groups having no significant difference in their rates of uterine atony (patients requiring more than one uterotonic agent).

Several reasons have been suggested for the higher magnitude of intraoperative blood loss in patients with obesity. One postulation relates to the effects of adipokines released from adipocytes on uterine contraction [24]. An in vitro study of myometrium collected from cesarean deliveries established that leptin had an inhibitory effect on spontaneous and oxytocin-induced myometrium contraction [25]. Other research found that high levels of adipokines were induced by high degrees of obesity, as there was a strong association between serum leptin concentration and the percentage of body fat [26]. The inhibitory effect of leptin on uterine contraction was confirmed by several studies on other adipokines, such as apelin, ghrelin, and visfatin [27–29].

Moreover, the calcium influx of myometrium cells involved in uterine contraction was previously reported to be lower in patients with obesity than in patients with a normal weight [30]. Furthermore, our results showed a significantly longer skin-incision-to-delivery duration and a longer total operating time in parturients with super obesity than in those with morbid obesity. This finding would be related to the technical difficulties of the surgery and the problematic field exposure arising from the greater thickness of subcutaneous fat in patients who are super obese. The reasons outlined above explain our finding of higher blood loss in the parturients who were super obese.

Our results showed that the overall rates of postpartum hemorrhage in parturients with morbid obesity and super obesity were 5.1 and 8%, respectively. Nevertheless, our study did not find any differences between the two groups regarding their uterine atony rates or their requirements for surgical intervention or intrapartum hysterectomy. In comparison, an investigation by Blomberg et al. revealed a rate of 5% for postpartum hemorrhage after a cesarean delivery in patients with a BMI ≥ 40 kg/m² [22]. Our result is consistent with the work by Smid et al. which demonstrated no differences in the uterine atony, reoperation, and hysterectomy rates of patients who were morbidly obese and those with super obesity [15].

Our study also revealed that the number of episodes of hypotension, the total volume of IV fluid administered, and the quantity of vasopressor used were higher in patients who were super obese. These results are similar to those of Elmeliegy, who reported that the total doses of ephedrine and phenylephrine were higher in patients with a BMI > 45 kg/m² who received spinal anesthesia for elective cesarean delivery [31]. In addition, the research by Lamon et al. found a greater extent of blockade in parturients with a BMI > 50 kg/m². The increased extent resulted in greater odds of a high spinal block (block-level ≥ T1) than for parturients with a BMI < 30 kg/m² [14]. The lower cerebrospinal fluid volume in patients with high BMIs results from their high abdominal pressure [32]. The chance of a higher level of blockade from regional anesthesia and a greater intraoperative blood loss contributes to the greater total fluid volume and use of vasopressors in parturients who are super obese. Nevertheless, our study failed to demonstrate a significant difference in the number of patients in the morbidly obese and super obese groups with spinal anesthesia levels above T4.

One of our patients suffered intraoperative cardiac arrest. The Confidential Enquiry into Maternal Deaths report revealed that, in the United Kingdom, maternal deaths related to anesthesia involved four patients with obesity and two with morbid obesity [33]. Another report from the United Kingdom (‘The CAPS Study’), which drew upon data from 2011 to 2014, showed that 12 of 16 patients who suffered cardiac arrest due to anesthesia complications were obese [34]. Compared with parturients of normal weight, pregnant women with obesity have higher risks of comorbidities and anesthetic-related complications, such as difficult intubation, diabetes, preeclampsia, and thromboembolic phenomenon [12,13,35]. Our patient suffered a massive pulmonary embolism, leading to intraoperative cardiac arrest. In a recent case report, a patient with a BMI of 109 kg/m² who underwent a cesarean delivery also had a history of cardiac arrest from a pulmonary embolism in a previous delivery [36]. These two cases highlight that parturients with obesity have higher risks from anesthesia and cardiac arrest in the peripartum period than pregnant women of normal weight. The risk of thromboembolism is an especially grave concern. The Royal College of Obstetricians and Gynaecologists in the United Kingdom has recommended using venous thromboprophylaxis during the peripartum period for patients with risk factors [37]. Patients with a BMI ≥ 30 kg/m² pre-pregnancy or in early pregnancy are considered at risk of developing thromboembolism [37].

A limitation of the current investigation is the questionable veracity of retrospective studies. In our case, data on the difficulty of neuraxial anesthesia, such as the number of spinal blocks attempted, could not be retrieved. Furthermore, the specific reasons for conversion to general anesthesia in patients with failed regional anesthesia were unknown. The anesthetic management decisions, such as the anesthesia techniques and the quantity and type of vasopressor required to maintain stable hemodynamics, mainly depended on the judgments of the attending anesthesiologists. These decisions would have inevitably varied among the anesthesiologists. Decisions relating to the medical and surgical management of postpartum hemorrhages would have also varied between the attending obstetricians. Lastly, the sample size of patients with a BMI of ≥50 kg/m² was far smaller than that of patients with a BMI of 40–49.9 kg/m². Therefore, further studies with larger super-obesity population sizes are needed to draw firm conclusions.

In conclusion, our data indicated that the degree of maternal obesity affects the rate of intraoperative hemorrhage and maternal outcomes. For parturients with morbid obesity or super obesity, awareness of the perioperative complications, preparation for the possible intraoperative adverse events, and meticulous anesthetic management are crucial. Additionally, preparations should be made for infrequent yet potentially life-threatening events, such as intubation failure, high spinal anesthesia, and maternal cardiac arrest. In addition, consideration must be given to strategies to prevent thromboembolic events. From a broader viewpoint, research should be undertaken on (1) the specific causes of intraoperative hemorrhage and (2) the optimum quantity and type of uterotonic agents for use with parturients who are morbidly or super obese and undergoing cesarean delivery.

Author contributions

PN: project development, conception and design, data analysis, interpretation of data, manuscript writing, and critical revision of the manuscript. TL: project development, data acquisition and interpretation, and manuscript writing. SM: project development, data acquisition and interpretation, and manuscript writing. NV: data acquisition and interpretation, and manuscript writing. All authors agree to be accountable for all aspects of the work.

Acknowledgements

The authors thank our hospital director, who gave permission for us to use and distribute patients’ data. Mr. Suthipol Udompunturak deserves special thanks for his major help with the statistical analyses. We are also indebted to Mr. David Park for the English-language editing of this paper. Finally, we thank Miss Chusana Rungjindamai for her capable administrative support.

Data availability statement

The dataset is available from the corresponding author upon reasonable request.

Disclosure statement

No potential conflict of interest was reported by the author(s).

Additional information

Funding

The author(s) reported there is no funding associated with the work featured in this article.