In line with the global obesity health epidemic, Australia-wide data show 46 per cent of pregnant women are either overweight (BMI 25–30) or obese (BMI ≥30)¹ and rates in rural areas are even higher, with over 65 per cent overweight or obese.² More significantly, the rates of high-order obesity are increasing; our local data at Western Health reveal over 6 per cent have morbid obesity (BMI≥40) and 1 per cent are super obese (BMI≥50). This prevalence means obesity is now considered to be the most common medical problem in pregnancy.³

Obesity is associated with a higher chance of adverse pregnancy outcomes including gestational diabetes, hypertension and pre-eclampsia, fetal macrosomia, induction of labour, prolonged labour and failure to progress, shoulder dystocia, failed instrumental delivery and postpartum haemorrhage (PPH).^{4 5} It is therefore not surprising that obese women have an increased risk of requiring theatre, whether for a caesarean section, trial of instrumental delivery or management of PPH. Despite the prevalence of obesity, there remains a lack of certainty about many risk-mitigation strategies for intraoperative and postoperative care. We will outline some practical approaches to help with the challenges of operating on obese parturients and update areas of uncertainty.

Capability assessment and preparation

Many maternity services transfer women above a particular BMI threshold (commonly BMI≥40) in recognition of capability constraints. While this can limit the chance of needing to manage a morbid- or super-obese pregnant woman, all services should have protocols in place in the event of an unplanned presentation. Incorporating morbid- or super-obese patient scenarios into simulation training (such as PROMPT) can support appropriate responses to unplanned presentations requiring theatre.

Equipment, positioning and personnel

Clear communication to theatre staff about morbidly obese patients will help ensure that appropriate personnel and equipment are available. Training in safe manual handling should be mandatory for all staff members involved. The weight limits of operating tables and stirrups should be clearly labelled, with the option of width extenders if necessary. Other required equipment includes lifts or hoists for transfer, longer surgical instruments and retractors, and appropriately sized blood pressure cuffs, thromboembolic deterrent stockings and pneumatic compression devices.^{3 6}

Obesity adds to total theatre time, with associated increased risk of pressure sores and neural injuries highlighting the importance of careful positioning to maximise surgical exposure while reducing injury.⁷ A 10–15 degree left lateral tilt is recommended to reduce the risk of supine hypotension, which is more pronounced in obese women, due to the added weight effect of the panniculus.⁸

Whether managing a PPH, instrumental or caesarean, the presence of senior, experienced staff (midwifery, nursing, anaesthetic and obstetric) can help limit operating times and support timely decision-making if any of the multitude of potential complications arise.

Anaesthetic considerations

Obesity and pregnancy are both known to cause physiological changes that increase the risk of anaesthetic complications. There is a higher incidence of other medical comorbidities that may complicate anaesthesia, such as obstructive sleep apnoea, hypertension, ischaemic heart disease and gastro-oesophageal reflux disorder.⁹

Regional anaesthesia (epidural or spinal) is preferred, but is more difficult due to adiposity and distortion of anatomical landmarks. Multiple attempts are often required and there is a higher failure rate.³ Although general anaesthesia is avoided whenever possible, it is more common in the obese obstetric patient.⁵ The challenges include higher rates of difficult intubation, aspiration and postoperative atelectasis.⁶ The obstetrician also needs to be aware of the increased anaesthetic and operating time required, which may necessitate alterations to planned elective lists and earlier recourse to caesarean section in unplanned cases.⁷

Consultation with an anaesthetist in the third trimester is recommended to undertake a risk assessment, additional testing as required and patient counselling. Although RCOG guidelines recommend routine anaesthetic consultation for women with a BMI of 40 or more, policies need to be individualised to local areas depending on the volume of patients, capacity and capability of the local anaesthetic department, and availability of antenatal and pre-operative education to women.⁶

Caesarean section

Wound asepsis

Obesity increases the risk of wound complications.¹⁰ When prepping the abdominal skin, it is important to ensure the area under the panniculus and the groin have also been thoroughly cleaned. Although not specific to the obese patient, a Cochrane review has shown that cleansing the vagina with iodine or non-alcoholic chlorhexidine pre-operatively probably reduces the risk of post caesarean section endometritis.¹¹

Antibiotics

Antibiotic prophylaxis prior to skin incision reduces the risk of wound complications and cephalosporins are commonly used.⁶ There remains uncertainty about optimum dosing in the obese population, with US guidelines suggesting 2 g cephazolin in patients less than 120 kg and 3g cephazolin in patients over 120 kg.⁸ Whatever dose is used, it is important to ensure administration 30–60 minutes before skin incision. This can be difficult to achieve and consideration of patient pathways to support this is likely to reduce infection rates.

Incision

There is ongoing debate regarding the optimal incision to facilitate good access to the pelvis and lower uterine segment, and to minimise the risk of wound complications.^{3 4} Senior involvement in deciding the appropriate incision and an individualised approach are recommended:

• A suprapubic transverse or Pfannensteil incision under the panniculus often has less adipose tissue and is closer to the pelvis; however, the incision sits in a moist anaerobic environment and is at risk of poor healing or infection.¹⁰ If a Pfannensteil incision is chosen, a panniculus retractor (such as Traxi®) can be useful in enhancing surgical site visualisation and reducing the number of staff required to assist.
• A transverse incision above the panniculus at the level of the umbilicus may be suitable for some women. With the abdominal wall anatomy distorted by a large panniculus, the umbilicus is more caudal than its usual position and a para or supraumbilical incision may offer good access to the uterus, although may hinder access to the lower uterine segment and increase the risk of a classical or vertical hysterotomy. This type of incision requires division of the rectus muscle and is more vascular, but has the strength of a transverse repair and avoids burying the wound under the panniculus. Transverse incisions are associated with less postoperative pain, enabling earlier mobility and improved respiratory effort.^{4 8}
• A midline incision may offer excellent exposure, but is associated with more postoperative pain and has increased wound complications when compared with a Pfannensteil incision.^{3 10}

Surgical considerations

To overcome the challenges of operating deep in the pelvis in an obese patient, the use of deep retractors, adequate lighting and longer instruments are helpful; the latter should be immediately available in theatre rather than being collected as the need arises. Meticulous haemostasis, closure of the recuts sheath, and closure of the subcutaneous adipose layer if 2cm or more, reduces the risk of wound complications.³ Subcutaneous drains have not been shown to reduce the risk of wound complications.⁴

Dressing

A prophylactic negative pressure wound therapy (NPWT) device may reduce the risk of wound complications; however, there is significant cost associated with using these and further research is needed before they can be routinely recommended.¹²

Postoperative care

General principles of postoperative care include adequate analgesia, early ambulation and early return to diet. Additional considerations include careful monitoring of respiratory and infectious morbidity, the need for high-dependency unit admission, and early physiotherapy involvement. Senior clinician review to ensure optimised postoperative care is required; the common practice of leaving the most junior member of the team to review postoperative obese mothers is inadequate.

Infections

Postoperative infections remain a major complication. There is a higher risk of endometritis and wound complications, including wound collections, infections and ⁶ Use of postpartum prophylactic antibiotics may be of benefit among obese women, although again, further research is needed before this can become recommended practice.¹³

Venous thromboembolism

Pregnancy, obesity and immobility all increase the risk of venous thromboembolism. Although guidelines vary internationally, there is consensus that early mobilisation, antithrombotic stockings and mechanical devices are recommended in addition to pharmacological prophylaxis during admission.⁶ 8 There is also potential benefit in weight-based dosing and some jurisdictions recommend prolonged low molecular weight heparin for up to six weeks for those at particularly high risk.¹⁴

Summary

Obesity is associated with increased obstetric risks and higher rates of theatre usage. Preparation, planning, practice, provision of suitable equipment and presence of senior experienced staff are important to mitigate risks. Other approaches such as NPWT devices, extended antibiotics, prolonged and dose-appropriate thromboprophylaxis should be considered, although the evidence base is still maturing and general recommendations remain hard to support given the potential costs and risks.

1. Australian Institute of Health and Welfare. A picture of overweight and obesity in Australia 2017. Cat no. PHE 216. Canberra: AIHW. Available from: www.aihw.gov.au/getmedia/172fba28-785e-4a08-ab37-2da3bbae40b8/aihw-phe-216.pdf.aspx?inline=true.
2. CE Cunningham, GR Teale. A profile of body mass index in a large rural Victorian obstetric cohort. MJA. 2013;198:39-42.
3. H Dutton, SJ Borengasser, LM Gaudet, et al. Obesity in Pregnancy: Optimizing Outcomes for Mom and Baby. Med Clin N Am. 2018;102:87-106.
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5. RANZCOG. Management of Obesity in Pregnancy (C-Obs 49). 2017. Available from: https://ranzcog.edu.au/Statements-Guidelines/Obstetrics/Obesity-in-Pregnancy,-Management-of-(C-Obs-49).
6. FC Denison, NR Aedla, O Keag, et al on behalf of the Royal College of Obstetricians and Gynaecologists. Care of Women with Obesity in Pregnancy. Green-top Guideline No. 72. BJOG. 2018.
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9. K Saravanakumar, SG Rao, GM Cooper. Obesity and obstetric anaesthesia. Anaesthesia. 2006;61:36-48.
10. LSM Machado. Cesarean section in morbidly obese parturients: Practical implications and complications. N Am J Med Sci. 2012;4(1):13-8.
11. DM Haas, S Morgan, K Contreras, et al. Vaginal preparation with antiseptic solution before caesarean section for preventing postoperative infections. Cochrane Database Syst Rev. 2018;7:DC007892.
12. L Yu, RJ Kronen, LE Simon, et al. Prophylactic negative-pressure wound therapy after caesarean is associated with reduced risk of surgical site infection: a systematic review and meta-analysis. Am J Obstet Gynecol. 2018;218(2):200-10.
13. AM Valent, C DeArmond, JM Houston, et al. Effect of post-cesarean delivery oral cephalexin and metronidazole on surgical site infection among obese women. JAMA. 2017;318(11):1026-34.
14. Better Safer Care Victoria. Obesity during pregnancy, birth and postpartum. Available from: www.bettersafercare.vic.gov.au/resources/clinical-guidance/maternity-ehandbook/obesity-during-pregnancy-birth-and-postpartum.