**4.1 Wound complications**

Wound complications – separation and infection, occur in approximately 10% of obese women delivered by cesarean [20, 25–27]. The odds ratio for wound complication in obese women is 1.14–1.65 times normal weight controls, when adjusted for many confounders [25]. There is a marked dose response for wound complications by increasing BMI category, with an odds ratio increase of up to 2.0 for every five-unit increment increase in BMI [28]. Chances of wound infection in super-obese women have been reported as high as 30% [29]. In probably the largest sample reported (38,229 women), wound complications occurred in 14% of women with BMI ≥ 45 kg/m2 following cesarean delivery [25]. Wound separations in particular are seen more frequently in patients with super obesity [30].

An increase in operative time in women who are obese is also dose dependent on BMI category [17, 27, 31]. Longer operative time is strongly correlated to post-operative infection, and may be a potential modifiable factor to reduce wound complication [32]. Other peri-operative and surgical strategies that may help prevent wound complications, such as pre-operative antibiotics, choice of skin incision, and wound closure type are reviewed in Section 4.4.

### **4.2 Thromboembolic events**

Other than cesarean delivery, obesity is the most common risk factor for a venous thromboembolic event (VTE) in pregnancy [33]. The classic Virchow's triad of hypercoagulability, endothelial injury, and stasis of blood flow leads to the well-established risk of VTE during pregnancy. Obesity itself, regardless of mode of delivery, is a significant risk factor for VTE, with reported risks of 1.7 to 5.3 (odds ratio) above normal weight controls [34–37]. Obese pregnant women have greater risk for pulmonary embolism than deep-vein thrombosis (DVT); the adjusted odds ratio for DVT is 4.4 (95% CI 1.6–11.9) and for pulmonary embolism is 14.9 (95% CI 3.0–74.8) [35]. Like other complications, VTE has a dose–response relationship with increasing BMI category [38].

The exact contribution of the combination of obesity and cesarean delivery to VTEs is difficult to quantify. Immobilization and high BMI have a multiplicative effect on risk for VTE [39]. It is very likely that obesity and cesarean delivery also have multiplicative effects on the chance for VTE. Prevention of VTE during cesarean delivery is discussed in Section 6.5.

#### **4.3 Neonatal outcomes**

Neonatal outcomes also appear to be influenced by maternal obesity at cesarean delivery. Neonatal morbidity, including low 5-minute Apgar scores (<7), umbilical cord arterial pH < 7.2, base excess ≤8 mmol/L, and neonatal intensive care unit admissions are seen more often in obese women who undergo cesarean delivery. Hypotension during spinal anesthesia, and prolonged puncture time for regional anesthesia is more pronounced in obese women, and has been shown to cause lower umbilical cord pH in obese women undergoing scheduled cesarean delivery [40, 41]. Women who are super-obese at the time of delivery have a 20% chance of neonatal intensive care unit admission [26]. There is a twofold odds increase of adverse neonatal event (low 5 min Apgar score, cardio-pulmonary resuscitation and ventilator support <24 h, neonatal injury, or transient tachypnea of the newborn, grade 3, 4 intraventricular hemorrhage, necrotizing enterocolitis, seizure, respiratory distress syndrome, hypoxic ischemic encephalopathy, meconium aspiration, ventilator support >2 days, sepsis and/or neonatal death) in women with super obesity compared to their normal weight controls [42]. Despite the tendency towards earlier cesarean delivery, the inherent delays and slower decision-to-incision and incision-to-delivery times involved in moving obese women to the delivery suite, and in getting the baby out when marked fetal distress is evident may contribute to adverse neonatal outcomes in some cases [43]. However, planned cesarean delivery is not protective against these risks, and suggests an underlying poorly understood biologic etiology may be the source of the increase in adverse neonatal outcomes seen in obese women.
