Pregnancy after bariatric surgery: screening for gestational diabetesBMJ 2017; 356 doi: https://doi.org/10.1136/bmj.j533 (Published 03 February 2017) Cite this as: BMJ 2017;356:j533
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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 . 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quote early pregnancy loss of 39% in support of their assertion ; however, this paper, which is more than twenty years out of date, reported on vertical banded gastroplasty, a long obsolete bariatric procedure, and did not prove a link between glycaemia and early pregnancy loss.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 , despite an expedited red blood cell turnover rate in pregnancy (from a usual 120 days to approximately 90 days ), and is not recommended for diagnosing gestational diabetes .
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 . 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.
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
We read with interest the above editorial by Adam et al published in the BMJ of 25th February 2017 1. It is a timely editorial, especially following the review article published in BMJ the week before on obesity and pregnancy 2. We fully agree with the author’s suggestions about having a standardized screening procedure for gestational diabetes (GDM) for these women who had undergone bariatric surgery.
Oral glucose tolerance test (OGTT) remains the mainstay to diagnose GDM 3. This is not useful amongst those who have undergone bariatric surgery because they had alteration of bowel anatomy and physiology 4. These leads to altered gastro-intestinal transit time and thereby higher risk of dumping syndrome. These increase the inaccuracy of this already fallible test 5. Unfortunately, the suggestion by the authors that this is still the currently preferred method in the UK is misleading as the study quoted was completed in October 2015 and had a response rate of only 22.5% from an electronic survey 6. 11 out of 27 responders used OGTT as the screening method, which clearly cannot support the statement ‘most are using the oral glucose tolerance test’.
Bariatric surgery improves the fertility rate in these women, but early pregnancy loss has been reported to be almost 39% 7. Hence, those pregnancies which did not have raised HbA1c at booking and remain viable by 2nd trimester of pregnancy should be screened for GDM at the earliest. The authors’ first suggestion of using self-monitoring of blood glucose (SMBG) from 14-16 weeks is a safer method. However, this is more expensive approach for these women, who face significant foeto-maternal complications conferred by the risk of residual obesity and coexisting dysglycaemic state. The second suggestion by the authors was SMBG before and after meals for a week between 24-28 weeks and the authors have cited NICE guideline NG3 to support their view 3. This guideline suggests ‘early SMBG’, without proscribing any gestational age or OGTT to be performed as soon as possible after booking. The OGTT is to be repeated at 24-28 weeks if the first OGTT is found to be normal. Hence, the notion of a week’s worth of SMBG so late in gestation, to diagnose GDM, is questionable. The authors also recommend screening by HbA1c in early pregnancy, which we fully agree; but their comment that it may delay in diagnosis is not conducive with the fact that most laboratories report HbA1c results on the very same day 8.
These discrepancies penned by a group of experts in this field and published in a reputed journal as the BMJ clearly exemplifies the confusion and controversies in this area of medical practice. We hope these could be laid at rest with a consensus statement or a guideline which we hope will be available soon.
(1) Adam S, Ammori B, Soran H, Syed AA. Pregnancy after bariatric surgery: screening for gestational diabetes. BMJ 2017; 356:j533.
(2) Catalano PM, Shankar K. Obesity and pregnancy: mechanisms of short term and long term adverse consequences for mother and child. BMJ 2017; 356:j1.
(3) NICE. Diabetes in pregnancy: management from preconception to the postnatal period. NG3. 2015. London, NICE.
Ref Type: Report
(4) Dirksen C, Damgaard M, Bojsen-Moller KN, Jorgensen NB, Kielgast U, Jacobsen SH et al. Fast pouch emptying, delayed small intestinal transit, and exaggerated gut hormone responses after Roux-en-Y gastric bypass. Neurogastroenterol Motil 2013; 25(4):346-e255.
(5) Mooy JM, Grootenhuis PA, de VH, Kostense PJ, Popp-Snijders C, Bouter LM et al. Intra-individual variation of glucose, specific insulin and proinsulin concentrations measured by two oral glucose tolerance tests in a general Caucasian population: the Hoorn Study. Diabetologia 1996; 39(3):298-305.
(6) 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):434-438.
(7) 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):42-44.
(8) Southend Hospitals pathology department. Glycated haemoglobin: pathology handbook. http://www southend nhs uk/pathology-handbook [ 2017 Available from: URL:http://www.southend.nhs.uk/pathology-handbook/test-directory/test-direct...
Competing interests: No competing interests