Bariatric surgical procedures

Bariatric procedures exhibit their effect on weight loss and comorbidity improvement through either a restrictive or a malabsorption mechanism, or a combination of both. The most common procedure performed in the UK is the gastric bypass (55%),1 with gastric sleeve and gastric banding performed less frequently. Most procedures are performed laparoscopically.

Gastric bypass surgery creates a small pouch that is separated from the rest of the stomach (Figure 1). The small intestine is divided in the middle of the jejunum into two limbs. The lower limb is attached via an anastomosis to the gastric pouch and the upper limb is attached further down the jejunum, bypassing the stomach, duodenum and proximal jejunum. The stomach pouch is only able to hold a small amount of food (restrictive); malabsorption occurs as a result of bypassing the proximal small bowel. The malabsorptive effect of gastric bypass requires lifelong supplementation to prevent nutrient deficiencies.11 Levels of fasting glucose, insulin, ghrelin (a hormone primarily responsible for appetite stimulation) and the gut hormone peptide-YY (an appetite regulant) are significantly altered following bariatric surgery and depend on the type of procedure performed.12 ,13 The gastric sleeve is a restrictive procedure that involves removing 80% of the stomach, leaving a sleeve-shaped organ (Figure 2). There is a theoretical impact on appetite suppression through reduced production of ghrelin, but its metabolic mechanisms are still not fully understood.14 It is proposed that the effect of the gastric sleeve on the absorption of oral hormones cannot be accurately determined at the present time, and this is an identified area for future research. Gastric banding involves placing an inflatable band around the upper portion of the stomach, which creates a small pouch above the site of the band, allowing for the size of the stomach opening to be adjusted by filling the band with a saline solution through a subdermal port. Gastric banding is reversible, and wholly restrictive with no malabsorptive component. The number of gastric banding procedures performed in the UK is declining due in part to high rates of removal and revision surgery attributed to patient intolerance, slippage, reflux and infection.15

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Figure 1

Diagrammatic representation of a Roux-en-Y gastric bypass procedure. Image reproduced with the kind permission of Dendrite Clinical Systems Ltd.

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Figure 2

Diagrammatic representation of a sleeve gastrectomy procedure. Image reproduced with the kind permission of Dendrite Clinical Systems Ltd.

Reproductive health and the bariatric patient

Fertility is negatively affected by obesity,16 but the rapid weight loss imposed by bariatric surgery means women will experience improved fertility,17 and be at risk of an unplanned pregnancy. There is no universal consensus on the timeframe, but the current advice to avoid pregnancy for at least 1 year, and possibly up to 2 years after surgery,7 ,9 is intended to reduce any theoretical risks to maternal and fetal health as a result of nutrient deficiencies and rapid weight loss.

Adverse maternal events may be lower in bariatric surgical patients compared with their obese counterparts. A retrospective study comparing 346 pregnant women who delivered before bariatric surgery with 354 women who delivered after bariatric surgery found a lower incidence of gestational diabetes (27% vs 8%).18 A systematic review that included three matched case-controlled studies by Maggard et al.,7 comparing women who had undergone bariatric surgery with obese controls, reported a reduced risk of developing pregnancy-induced hypertension and pre-eclampsia, along with lower rates of gestational diabetes. In addition, some studies suggest fewer neonatal complications such as premature delivery, macrosomia and low birth weight following bariatric surgery compared to obese controls.7 ,9

Thus the choice of contraceptive method in bariatric patients requires careful consideration to ensure that it is effective, acceptable to the woman, and that pregnancy is avoided.

Absorption of oral contraceptives following bariatric surgery

Adaptation to post-surgical life includes changes to eating habits that may result in vomiting and diarrhoea, known causes of breakthrough bleeding, and reduced efficacy in women taking all types of oral contraceptives. Vomiting and diarrhoea may occur with all procedures, and are generally a result of poor food choices.19 Other causes of vomiting include food becoming stuck (banding and sleeve) and anastomotic stenosis, narrowing of the new connection between the stomach and lower intestine (gastric bypass). Frequent or prolonged vomiting should always be investigated.

The pharmacokinetics of oral contraception is affected by the type of procedure performed. Oral estrogen is mostly absorbed in the upper gastrointestinal tract, which is reshaped as a result of bariatric surgery, particularly with gastric bypass as this altered digestive physiology results in malabsorption. The United States Medical Eligibility Criteria for Contraceptive Use advises against oral contraceptives in bariatric patients.20 A ‘before and after’ comparison study of the pharmacokinetics of an ethinylestradiol/levonorgestrel contraceptive pill 1 month before and 4 months post-gastric bypass is currently recruiting surgery-seeking females aged between 18 and 40 years. The primary outcome measure is twice-weekly serum hormone levels before and after surgery; the secondary outcome measures include twice-weekly endometrial thickness measured by transvaginal ultrasound for the duration of the study.21

Currently it is thought that the efficacy of progestogen-only pills and emergency contraception pills following malabsorptive procedures may be reduced and are not recommended.20

No evidence was found to suggest a reduction in the effectiveness of oral hormones following restrictive procedures.20

Non-oral contraceptive use following bariatric surgery

Patients experience significant weight loss after surgery, resulting in loose skin, which may affect contraceptive choices (e.g. there is anecdotal evidence to suggest difficulties in finding a suitable site for applying transdermal patches and making insertion of subdermal implants technically more difficult).

A study of three case reports of obese women (preoperative BMI range 51.8–64.7 kg/m²) with etonogestrel implants inserted prior to gastric bypass showed that levels of etonogestrel decreased with weight loss, but these levels remained sufficiently high to provide contraceptive efficacy.22

It is thought that the association of weight gain with injectable methods23 may be unacceptable to bariatric patients. In addition, the existing potential for bone mineral density loss with injectable methods23 that may also occur with bariatric procedures17 is still under investigation, so this method should be regarded with caution at present.

Obese women may find vaginal rings, female condoms, diaphragms and cervical caps difficult to insert and intrauterine contraceptive threads difficult to check. Guidance for diaphragm users recommends visiting a health care professional to check the correct sizing of this barrier method following a weight change of 3 kg,23 making this an impractical choice for bariatric patients.

The psychosocial impact of bariatric surgery is known to affect interpersonal relationships;24 irreversible methods of contraception such as male and female sterilisation or non-surgical blockage of the Fallopian tubes (Essure^®), leading to permanent lifestyle changes, should be carefully considered following bariatric surgery to avoid later regret.

Suggested contraceptive methods for bariatric patients

Based on current UK and USA contraceptive guidelines20 ,23 for obese women, and accounting for the theoretical risk for bariatric procedures to reduce oral hormone absorption, intrauterine devices (IUDs) (either hormonal or copper) should be offered as a first-line contraceptive method for bariatric patients. IUDs offer long-term reversible contraception that is not affected by surgically imposed weight loss or malabsorption, but the device threads may be difficult to check until significant weight loss is achieved. Current UK contraception recommendations for obese women do not assess the impact of bariatric procedures.23 Table 1 is a proposed guide to contraception recommendations for obese women, based on the format of the UK Medical Eligibility Criteria for Contraceptive Use,23 and assumes a postoperative BMI of at least 35 kg/m², based on NICE minimum weight eligibility criteria for bariatric surgery.

Male condoms are also an option; but as a patient's weight decreases, the range of contraceptive options increases. The risk of adverse events associated with specific contraceptive methods, obesity, pregnancy and surgical procedure must be balanced against the needs of the individual bariatric patient.