Intended for healthcare professionals


Pregnancy after bariatric surgery: screening for gestational diabetes

BMJ 2017; 356 doi: (Published 03 February 2017) Cite this as: BMJ 2017;356:j533
  1. Safwaan Adam, clinical research associate1 2 3,
  2. Basil Ammori, honorary professor of surgery1 2,
  3. Handrean Soran, consultant physician and endocrinologist1 3,
  4. Akheel A Syed, honorary senior lecturer1 2
  1. 1Faculty of Biology, Medicine and Health, University of Manchester, Manchester, UK 2Salford Royal NHS Foundation Trust, Salford, UK
  2. 3University Department of Medicine, Central Manchester University Hospitals NHS Foundation Trust, Manchester, UK
  1. Correspondence to: S Adam s.adam{at}

Safer alternatives are needed to traditional test

Obesity affects a quarter of adult women in the UK, western Europe, and Canada, and a third in the US. More women than men have bariatric surgery every year,1 and most are of childbearing age. Of 12 869 women in the UK who had primary bariatric surgery in 2011-13, 8469 (66%) were younger than 50.1 Furthermore, fertility in obese women generally improves after bariatric surgery as menstrual irregularity and ovulatory problems resolve with weight loss.23 Thus, increasing numbers of women with obesity start or complete their families after bariatric surgery.

Despite weight loss after surgery, many women still require screening for gestational diabetes mellitus during pregnancy. A history of bariatric surgery has important implications for the choice of test since an oral glucose tolerance test can trigger dumping syndromes, with serious adverse effects.

The two most common primary bariatric procedures, Roux-en-Y gastric bypass (54%) and sleeve gastrectomy (20%),1 can both cause dumping syndromes because they surgically alter gastric reservoir function.4 Early dumping results from rapid delivery of hyperosmolar chyme to the upper small bowel, which induces release of vasoactive gut hormones such as vasoactive intestinal peptide, neurotensin, glucagon-like peptide 1, and glucagon dependent insulinotropic peptide. Symptoms appear 10–60 minutes after food and can include abdominal pain, bloating, borborygmus, nausea, diarrhoea, fatigue, flushing, palpitations, perspiration, tachycardia, hypotension, and, rarely, syncope.24 Late dumping occurs 1–3 hours after a meal, when a hyperinsulinaemic response to ingested carbohydrate produces postprandial reactive hypoglycaemia. Clinical manifestations can include fatigue, weakness, confusion, hunger, perspiration, palpitations, tremor, irritability, and syncope.

An oral glucose tolerance test in patients who have had bariatric surgery carries a high risk of both early and late dumping because of high osmolality and glucose loading. This presents a particular challenge in screening for gestational diabetes. Hyperglycaemia in pregnancy affected an estimated 20.9 million (16%) of live births in 2015, in 85% of which the mother had gestational diabetes.5 The UK recommends screening for gestational diabetes with a two hour 75 g glucose tolerance test at 24-28 weeks’ gestation in women who have a body mass index over 30, a history of fetal macrosomia, previous gestational diabetes, family history of diabetes, or who belong to high risk ethnic groups.6 Although bariatric surgery reduces the risk of gestational diabetes,7 as the lowest body mass index after surgery exceeds 30 in 66% of women of childbearing age,3 most such women will qualify for screening on at least one criterion.

We know of no guidelines for screening for gestational diabetes in women who have had bariatric surgery. Wide variations in glucose excursions in pregnant women after bariatric surgery make diagnosis difficult.89 Intriguingly, a survey of midwives in the UK found that most are using oral glucose tolerance tests.10 However, test induced dumping syndrome can lead to inaccurate results and pose significant risk: studies have reported reactive hypoglycaemia in 55%8 and adverse events (including hypoglycaemia) in 65% of women.11

We suggest that obese women who have had bariatric surgery should be deemed high risk for gestational diabetes and be screened using one of two approaches. The first would be capillary blood glucose monitoring, starting at 14 to 16 weeks of gestation and continuing throughout the pregnancy, similar to the recommendation for women with previous gestational diabetes.6 The second would be to record capillary blood glucose daily before and after meals for a week at 24 to 28 weeks’ gestation. This may prove more acceptable to pregnant women and less demanding of scarce healthcare resources. The diagnostic or intervention thresholds for either approach would be >5.3 mmol/L before meals, >7.8 mmol/L one hour after eating, and >6.4 mmol/L two hours after eating.6

We also recommend measuring glycated haemoglobin at the first antenatal visit to exclude pre-existing diabetes in all women who have had bariatric surgery612; its use for screening for gestational diabetes, however, is not supported by robust evidence and may delay diagnosis. Continuous glucose monitoring profiles are similar in pregnant and non-pregnant women after gastric bypass and have been suggested as another approach to screening after bariatric surgery.9 Continuous monitoring, however, is expensive and not widely available. Continuous glucose monitoring and capillary blood testing have not yet been shown to influence perinatal outcomes. Both approaches deserve further research.

With the growing popularity of bariatric surgery, guidelines are urgently needed for managing gestational dysglycaemia in women who have had surgery, encompassing preconception care, screening for diabetes, and management of hyperglycaemia and hypoglycaemia in pregnancy. Guidance is also required on nutritional supplements, since micronutrient deficiencies could theoretically contribute to adverse pregnancy outcomes.2


  • Competing interests: We have read and understood BMJ policy on declaration of interests and have no interests to declare.

  • Provenance and peer review: Not commissioned; externally peer reviewed.


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