Editorials

Pregnancy after bariatric surgery: screening for gestational diabetes

BMJ 2017; 356 doi: https://doi.org/10.1136/bmj.j533 (Published 03 February 2017) Cite this as: BMJ 2017;356:j533

Re: Pregnancy after bariatric surgery: screening for gestational diabetes

We thank Dr Banerjee and colleagues for their comments on our editorial and we wish to take this opportunity to clarify one or two points. Our premise that the oral glucose tolerance test is the common screening test for gestational diabetes in women who have had bariatric surgery is readily borne out by personal experience that includes follow-up of a large cohort of bariatric surgical patients, discussions with colleagues with a specialist interest in bariatric management nationally and online discussion boards that bear witness to patient testimonies. Whereas surveys are not always completely representative of the full range of clinical practice, the report by Whyte and colleagues provides corroborative insights [1]. In this survey, 26 of 27 respondents had managed pregnant women post-bariatric surgery and therefore encountered this clinical scenario; 18 respondents answered about their preferred diagnostic test for gestational diabetes; 11 of the 18 (61%) opted to use the oral glucose tolerance test, leading to the authors’ conclusion that this was the most performed test.

Dr Banerjee and colleagues urge screening for gestational diabetes at the earliest in those women with a viable second trimester pregnancy that did not have raised glycated haemoglobin (HbA1c) at the antenatal booking appointment. They quote early pregnancy loss of 39% in support of their assertion [2]; however, this paper, which is more than twenty years out of date, reported on vertical banded gastroplasty, a long obsolete bariatric procedure, and did not prove a link between glycaemia and early pregnancy loss. We would offer reassurance to Dr Banerjee and colleagues that pregnancy outcomes with modern bariatric management are often superior to that seen in women matched for level of obesity and arguably comparable to the general obstetric population [3-5]. Our comment (within the editorial) regarding delay in diagnosis when using HbA1c was in reference to diagnosing gestational diabetes, not laboratory processing times. Whilst HbA1c can give an indication of chronic glycaemia, rises in HbA1c will lag behind those of glucose in more acute hyperglycaemia [6], despite an expedited red blood cell turnover rate in pregnancy (from a usual 120 days to approximately 90 days [7]), and is not recommended for diagnosing gestational diabetes [8].

Our recommendation for a safer alternative to the oral glucose tolerance test for screening of gestational diabetes in women who have had bariatric surgery was borne of pragmatism. Capillary blood glucose testing pre- and post-meals starting from the early second trimester and continuing throughout the pregnancy would require considerable personal investment of time and commitment on the part of patients and healthcare professionals and not insignificant healthcare costs. Whilst individual patients may choose to opt for this strategy in discussion with their antenatal and bariatric healthcare professionals, it is idealistic when placed in the context of a reduced risk of gestational diabetes in these women [5, 9]. The second approach of capillary blood glucose testing for a week between 24 to 28 weeks’ of gestation reflects the peak time of onset of hyperglycaemia in pregnancy. Screening for gestational diabetes at this point in pregnancy is well entrenched in antenatal practice supported by national guidance [8]. Arguably a week’s worth of blood glucose monitoring better reflects glucose handling in all pregnant women requiring screening for gestational diabetes, let alone those that have undergone bariatric surgery, than a snapshot oral glucose tolerance with all its foibles and fallibilities. We would urge that a comprehensive discussion between healthcare professionals and patients about all safe gestational diabetes screening approaches is carried out at the first antenatal booking appointment before mutually deciding on a method.

Finally, we concur that specific guidance is needed for diagnosing and managing gestational glycaemia in women post-bariatric surgery. We hope that our editorial and any debate that it has stimulated will enrich the development of a comprehensive clinical guideline.

References

1. Whyte M, Johnson R, Cooke D, Hart K, McCormack M, Shawe J. Diagnosing gestational diabetes mellitus in women following bariatric surgery: A national survey of lead diabetes midwives. British Journal of Midwifery. 2016;24(6):434-8.
2. Bilenka B, Ben-Shlomo I, Cozacov C, Gold CH, Zohar S. Fertility, miscarriage and pregnancy after vertical banded gastroplasty operation for morbid obesity. Acta Obstet Gynecol Scand. 1995;74(1):42-4.
3. Narayanan RP, Syed AA. Pregnancy Following Bariatric Surgery-Medical Complications and Management. Obes Surg. 2016;26(10):2523-9.
4. Alatishe A, Ammori BJ, New JP, Syed AA. Bariatric surgery in women of childbearing age. QJM. 2013;106(8):717-20. Epub 2013/04/12.
5. Johansson K, Cnattingius S, Naslund I, Roos N, Trolle Lagerros Y, Granath F, et al. Outcomes of pregnancy after bariatric surgery. N Engl J Med. 2015;372(9):814-24.
6. Kilpatrick ES, Atkin SL. Using haemoglobin A1c to diagnose type 2 diabetes or to identify people at high risk of diabetes. BMJ. 2014;348(apr25 3):g2867-g.
7. Radin MS. Pitfalls in hemoglobin A1c measurement: when results may be misleading. J Gen Intern Med. 2014;29(2):388-94.
8. Diabetes in pregnancy: management from preconception to the postnatal period. London: National Institute for Health and Care Excellence; 2015; Available from: https://www.nice.org.uk/guidance/ng3/.
9. Yi XY, Li QF, Zhang J, Wang ZH. A meta-analysis of maternal and fetal outcomes of pregnancy after bariatric surgery. Int J Gynaecol Obstet. 2015;130(1):3-9.

Competing interests: No competing interests

20 March 2017
Safwaan Adam
Clinical Research Associate
Dr Akheel A Syed
3rd Floor, Core Technology Facility, University of Manchester, 46 Grafton St., M13 9XX
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