Pregnancy after bariatric surgery: Consensus recommendations for periconception, antenatal and postnatal care

1American Diabetes Association

2Adjustable gastric band

3Body mass index

4Biliopancreatic diversion

5Bariatric surgery

6Capillary blood glucose

7Continuous glucose monitoring

8Combined oral contraception

9Fetal growth restriction

10Fasting plasma glucose

11Gestational diabetes mellitus

12Glycaemic index

13Gestational weight gain

14International normalized ratio

15Institute of Medicine

16Intrauterine device

17Intrauterine system

18Long‐acting reversible contraception

19Large for gestational age

20Neonatal intensive care unit

21Oral glucose tolerance testing

22Postprandial hyperinsulinaemic hypoglycaemia

23Parathyroid hormone

24Roux‐en‐Y gastric bypass

25Sleeve gastrectomy

26Small for gestational age

27Type 2 diabetes

28World Health Organization

29The prevalence of obesity worldwide has nearly tripled between 1975 and 2016. In 2016, 1.9 billion adults aged 18 years or older (40% of women and 39% of men) were affected by overweight (BMI 25‐29 kg/m2) with 650 million (11% men and 15% women) having obesity (BMI ≥ 30 kg/m2).1 Obesity increases complications for both mother and offspring during pregnancy and childbirth.2 Furthermore, there is growing evidence that parental nutrition and lifestyle affect embryonic development with potential long‐term health implications for the infant through on the process of developmental programming.3, 4 As such, it is generally recommended that both women and men with obesity lose weight before conception.5, 6 Based on international guidelines,7 patients with class III obesity (BMI ≥ 40 kg/m2) or class II obesity (BMI 35‐39 kg/m2) with associated comorbidities may be eligible for bariatric surgery (BS). Poor success with weight loss by diet alone has led to BS becoming increasingly popular.8 Common procedures include (1) sleeve gastrectomy (SG), the most frequently performed operation,9 in which the greater curvature of the stomach is resected, reducing stomach volume by 75%, thus limiting food intake. This procedure also removes ghrelin‐producing secreting endocrine cells present in the greater curvature of the stomach, which aid in appetite reduction. Weight loss as well as alterations in other metabolic hormones results in the improvement of glucose homeostasis and results in positive effects on comorbidities therefore reducing appetite and aiding in subsequent diabetes remission.10 (2) Roux‐en‐Y gastric bypass (RYGB), a mixed procedure in which the volume of the stomach is reduced to approximately 15 to 30 mL and the absorption of nutrients, is impaired by bypassing part of the small intestine and diverting the food flow to the distant small intestine. This approach not only results in a limited oral intake but also induces malabsorption, although this is reduced over time because of intestinal hypertrophy. Furthermore, an increase in gut hormone secretion (including GLP‐1 and PYY) hormones associated with RYGB may diminish appetite and result in better glucose homeostasis.11 (3) Adjustable gastric band (AGB) procedures where an inflatable restrictive band is placed around the upper portion of the stomach creating a small pouch with a narrow opening to the lower stomach, adjusted by adding or removing fluid to the band via a subdermal port. This reduces stomach capacity and appetite.12 Other types of surgery include biliopancreatic diversion with duodenal switch, intragastric balloon, and vertical banded gastroplasty, but these are outdated or rarely performed.

30As a result of weight loss and enteroendocrine alteration, BS has also been shown to reduce the incidence of obesity‐related comorbidities and complications.13 BS is however associated with a potential increase in adverse events due to surgical complications and micronutrient deficiencies and derangements in (neuro)endocrine and metabolic homeostasis.14, 15, 16, 17 Approximately 80% of BS is in women, many of whom are of reproductive age.18, 19, 20 BS may improve fertility through restoration of ovulation, and pregnancies after BS are becoming increasingly common.21 It has been recognized that changes in gut anatomy and physiology with potential for malnutrition incur increased potential for adverse perinatal outcomes such as small for gestational age (SGA), preterm birth, congenital abnormalities, and perinatal mortality. Pregnancy soon after surgery may increase risk of maternal morbidity and/or mortality.22

31A need for more specific guidance and nutritional management was recognized, and an international group of experts was assembled to review the available evidence and provide recommendations on the periconception, antenatal, and postnatal care of pregnancies after BS.

32An expert meeting focused on pregnancy after BS was organized at the University of Surrey, UK in April 2017 with a follow‐up meeting at University Hospital Leuven, Belgium, in November 2017. These meetings brought together national and international expertise from a multidisciplinary group of researchers and clinicians including specialists in obstetrics and gynaecology, bariatric surgery, endocrinology, dietetics, nutrition, nursing and midwifery, health psychology, epidemiology, and public health. Additional international colleagues were able to join both meetings through teleconferencing.

33The objectives of the meetings were to discuss the key questions, to advance scientific knowledge and practice in the area of pregnancy after BS, and to identify key areas of focus for collaborative work to produce consensus clinical guidelines on best practice for facilitating healthy pregnancies after BS.

34The clinical guideline was developed using the structure from ADAPTE.23 The group formulated specific clinical questions in relation to pregnancy after BS (Table 1). For each question, a systematic search of the available literature was performed, identifying articles published from inception to July 2018. Search terms related to pregnancy (“pregnancy,” “prepregnancy,” “mother,” “maternal,” “conception,” “preconception,” “gravid,” “pregravid”) were combined with terms related to BS (“bariatric surgery,” “weight loss surgery,” “gastric bypass,” “Roux‐en‐Y,” “RYGB,” “sleeve gastrectomy,” “gastric sleeve,” “gastroplasty,” “gastric band,” “LAGB,” “biliopancreatic diversion,” “BPD,” “duodenal switch”) and terms specific for each clinical question. Articles resulting from these searches and relevant references cited in those articles were reviewed. All evidence was graded (Table 2)24 and discussed during group meetings. When evidence of sufficient quality was lacking, the group made consensus recommendations based on expert clinical experience. Consensus on the guidelines was declared when 100% of the group agreed with the recommendations. The final document was reviewed by all authors. The recommendations made by this group are summarized in Table 3.

35The period after BS is characterized by weight loss which may be rapid after SG and RYGB procedures and slower after AGB, once optimal adjustment has been achieved. During this period postsurgery,25, 26 women are recommended to postpone pregnancy in order to ensure maximal weight loss, weight stabilization, and to reduce the risk of macronutrient and micronutrient deficiencies and electrolyte imbalances.5 Evidence in regard to this recommendation is however scarce. We identified 14 studies reporting on the surgery‐to‐conception interval and pregnancy outcomes, but many studies have limitations in methodology thus preventing comparison.

36Parent et al22 found that a shorter surgery‐to‐birth interval (less than 2 years) was associated with a higher risk for prematurity, SGA, and neonatal intensive care unit (NICU) admission (level 2++), but data on long‐term outcomes were missing. In contrast, Stentebjerg et al27 and Nomura et al28 found an increased risk for certain pregnancy complications (iron deficiency, excessive gestational weight gain (GWG), and delivery by caesarean section) if the pregnancy was postponed according to this recommendation (level 2+). Norgaard et al29 found no difference in the prevalence of SGA prior to, or after, 18 months (level 2++). Other studies also did not find a difference in gestational outcomes according to surgery to conception interval.27, 30, 31, 32, 33, 34, 35, 36, 37

37Based on level 2++ evidence, the members of this group recommend postponing pregnancy until a stable weight is achieved. This is typically achieved 1 year after SG or RYGB procedures and 2 years after AGB.

38Women recommended to postpone pregnancy during the period of rapid weight loss (1‐2 years) require adequate counselling regarding safe and effective contraception.38 As obesity is associated with impaired fertility due to metabolic syndrome and PCOS, patients may not be using contraception presurgery. They should be made aware that fertility increases postoperatively, and contraception usage should be discussed (level 2+).39 There is sufficient evidence to show that perioperative contraceptive counselling increases the postoperative use of contraception (level 2+).40, 41 Contraceptive counselling and contraceptive knowledge by health care providers could however be improved (level 2−),42, 43 as contraceptive use after BS is often suboptimal, with many women using least reliable methods (level 2+).39, 40, 44, 45, 46, 47, 48 This is even more important in patients with a history of infertility, as they have been found to be at increased risk for unprotected intercourse without intent to conceive and have higher early postoperative conception rates.39

39Both RYGB and, to a lesser extent, SG significantly alter the anatomical structure of the gastrointestinal tract, and theoretically, this gut shortening could affect the absorption of oral contraceptives containing an oestrogen component which undergoes metabolism in the upper gut wall. Absorption of ethinylestradiol from the contraceptive pill may be reduced leading to a decrease in efficacy.49 Reliability might also decrease due to postoperative side effects and complications such as vomiting and/or diarrhoea; however, there are few data in women after BS. Limited clinical evidence suggests no substantial decrease in effectiveness of oral contraception among women who underwent a biliopancreatic diversion (BPD), a now uncommon procedure, or AGB.50, 51 However, evidence from pharmacokinetic studies has shown increased contraceptive failure for progestogen oral contraception among women who underwent a jejunoileal bypass (an older procedure).52, 53 In general, combined oral contraception (COC) may be less reliable after BS (level 2+).51 Additionally, many individuals are still affected by obesity after BS, and this represents a relative contraindication for the use of COC, with both factors increasing the risk of venous thromboembolism.38 Alternatives found to be unaffected by BS are parenteral long‐acting reversible contraception (LARC) methods such as the copper intrauterine device (IUD), intrauterine systems (IUS), and progestogen implants. They have been found to be highly effective and acceptable to women (level 2−).54, 55, 56, 57 For women choosing nonhormonal barrier methods, both male and female condoms may be suitable; however, the contraceptive diaphragm may be difficult to insert correctly and less reliable as it requires refitting after every 3 kg of weight change.58

40Consensus from available evidence is that women should receive counselling regarding contraception prior to surgery (level 2−). Combined oral contraception containing oestrogen should be avoided after BS (level 2+). The use of long‐acting reversible contraception such as implants, IUD, or IUS should be encouraged and offered as first line following BS (level 2−).

41A large proportion of pregnant women have a poor diet,59 independent of BS history. The focus should remain on the regular monitoring of diet quality and nutritional status and on encouraging a general healthy dietary pattern and lifestyle.3 At the same time, a healthy diet post‐BS may differ in food group proportions from that of the nonsurgical pregnant population. This is due to a greater emphasis on lean protein sources, followed by fruit and vegetables, and lastly starchy carbohydrates, as the main component of the post BS diet. There is little or no evidence‐based specific dietary (food‐based) advice for pregnancies post BS and few published reports of the dietary intakes of this population.60 It therefore seems prudent to combine what we know about an appropriate postsurgical diet with the accepted general dietary advice for pregnancy to provide appropriate guidance.

42Energy requirements should be individualized on the basis of prepregnancy BMI, GWG, and physical activity level, with limitations on energy‐dense foods if excessive GWG is identified (level 2+).60 Beard et al61 recommend a minimum of 60 g of protein/day during pregnancy post‐BS (level 4). However, subsequent antenatal achievement of protein requirements is more difficult following bypass operations.62 In the nonpregnant postsurgical patient, intakes of up to 1.5 g/kg ideal body weight/day are proposed (up to a maximum of 2.1 g/kg).63 How this translates into pregnancy and in particular how ideal body weight should be defined have not been studied.

43Exposure to abnormal glucose levels during pregnancy, similar to that seen in nonsurgical women with GDM, warrants dietary intervention. In the case of hyperglycaemia, it is recommended to reduce rapidly absorbed carbohydrates, substituting them with protein and low glycaemic index (GI) alternatives (level 4).

44Parenteral nutrition support may be indicated in cases of severe malnutrition during pregnancy64 with initiation and choice of feeding route informed by local nutrition support protocols (level 4). In the absence of dietary advice specific to the postsurgery population, women should be encouraged to adhere to national guidelines regarding diet, taking into consideration changes of anatomy due to BS.

45Postprandial syndrome, or dumping syndrome, is a common effect of bariatric and metabolic surgery. Postprandial syndrome (also termed early dumping syndrome) occurs within 60 minutes of ingestion of food, typically rapidly absorbed carbohydrates, producing symptoms including dizziness, flushing, and palpitations. If early dumping is suspected, rapidly absorbed carbohydrates should be avoided. Additionally, liquids should not be taken 30 minutes before and after eating to encourage a slower gastric transit (level 2−).65, 66 Caffeinated beverages should be avoided, and patients should be advised to eat slowly and chew well. Individualized advice relating to portion sizes and meal/snack frequency and spacing may be helpful alongside education about the GI of different foods (level 4).66 Alcohol consumption can precipitate dumping and is in general contraindicated throughout pregnancy.67

46Late dumping or postprandial hyperinsulinaemic hypoglycaemia (PHH) is far less common, although the exact prevalence remains unclear due to the lack of clear diagnostic criteria.68, 69, 70 PHH characterized by symptomatic hypoglycaemia that occurs after 60 minutes of eating (typically between 60 and 180 minutes postprandial).71 This syndrome should be considered in those who have symptoms of hypoglycaemia (eg, altered mental state, anxiety, sweating, or altered sensorium) that occur in parallel with biochemical evidence of hypoglycaemia, and which then resolve on ingestion of carbohydrate (ie, symptoms agree with Whipple's triad).71

47In general, management of late dumping/PHH requires more careful dietary manipulation (ie, low GI carbohydrates, small carbohydrate portions, carbohydrates mixed with protein, frequent intake of six small meals) and sometimes referral to an endocrinologist for further investigation and medical management (level 4).72 There is no specific approach for PPH described in pregnancy, although important glycaemic excursions potentially could affect fetal growth and well‐being.

48Men and women after BS have an increased risk to develop micronutrient deficiencies.73 In the formulation of this guidance, it is recognized that there is a lack of evidence on the optimal nutritional monitoring and supplementation strategies in pregnancy after BS. We have therefore used data and guidelines for the nonpregnant postoperative population and supplemented this with pregnancy‐specific data when available. It should be noted that we recommend that pregnancy should be planned and that nutritional supplementation should be optimized preferably 3 to 6 months prior to conception (level 4). A multivitamin and mineral supplement should be taken daily prior to conception and throughout pregnancy (level 4). This supplement should contain the following at a minimum: copper (2 mg), zinc (15 mg), selenium (50 μg), folic acid (5 mg), iron (45‐60 mg or >18 mg after AGB), thiamine (>12 mg), vitamin E (15 mg), and beta‐carotene (vitamin A, 5000 IU) (level 4). The retinol form of vitamin A should be avoided during pregnancy due to teratogenicity risk (level 2+),74, 75 and supplementation should be adjusted to maintain concentrations within normal limits (level 2−).76

49Given the risk associated with potential deficiencies in the periconception period, the following indices should be checked at least every 3 months in women planning to become pregnant after BS: serum folate or red blood cell folate (level 2−),77 serum vitamin B12 or transcobalamin (level 2−),62, 63, 73, 78, 79 serum ferritin, iron studies (including transferrin saturation), full blood count (level 2−),63, 73, 76, 78, 79 and serum vitamin A levels (level 2−).76, 80, 81 In addition, the following should be monitored every 6 months: prothrombin time, international normalized ratio (INR) (level 2+),82, 83 serum 25‐hydroxyvitamin D with calcium, phosphate, magnesium, and parathyroid hormone (PTH) (level 4), serum protein and albumin (level 2−),62, 78 renal function and liver function tests (level 4), serum vitamin E (level 4), serum zinc, copper, and selenium (level 4). Serum vitamin K1 concentration should be monitored if coagulation studies are abnormal (level 2+).83

50Specific supplementation is recommended in the preconception and periconception period (Tables 3 and 4). In most patients after BS, 0.4 mg per day of folic acid is sufficient as doses >0.3 mg are not absorbed, due to lack of dihydrofolate reductase in intestinal cells. Despite having undergone BS, many patients still have a BMI > 30 kg/m2. Current guidelines suggest that additional folic acid at a dose of 4 or 5 mg daily should be given to these patients during the periconception period and throughout the first trimester (level 4).84 Postsurgery vitamin B12 regimens should be continued preconception at a dose of 1 mg every 3 months via intramuscular depot injection. Alternatively, oral supplementation (1 mg/day) can be used to increase compliance in the patient. However, a reduced absorption is to be expected as the secretion of intrinsic factor is diminished (level 4).85 Additional vitamin B12 supplementation should be given as needed to maintain serum concentrations within normal limits (level 4). Iron supplementation should be continued at a minimum dose of 45 mg of elemental iron daily (>18 mg for AGB); this should be increased as needed to maintain ferritin within normal limits (level 4). Vitamin D should be supplemented to maintain a concentration of 50 nmol/L or greater with a serum PTH within normal limits (level 4). Calcium should be added to on‐going vitamin D supplementation as needed to maintain PTH within normal limits (level 4). If vitamin K1 deficiency is measured or suggested by coagulation defects, it is advised to supplement this with an oral dose of 10 mg weekly (level 2+).83

51During pregnancy, serum levels of many micronutrients and macronutrients will decrease as a result of the expanding maternal blood volume and increasing demands of the growing fetus. Therefore, it is recommended to check the following indices at least once per trimester and use pregnancy‐specific ranges: serum folate (level 2−)77; serum vitamin B12 (level 2−)62, 63, 73, 78, 79; serum ferritin, iron studies including transferrin saturation and full blood count (level 2−)63, 73, 76, 78, 79; serum vitamin D with calcium, phosphate, magnesium, and PTH (level 4); serum vitamin A (level 2−)76, 80, 81; prothrombin time, INR, and serum vitamin K1 concentration (level 2+)82, 83; serum protein and albumin (level 2−)62, 78; and renal function and liver function tests (level 4). In addition, we advise to monitor serum vitamin E, serum zinc, copper, and selenium (level 4) during the first trimester.

52During pregnancy, thiamine 300 mg daily with vitamin B complex should be prescribed if prolonged vomiting occurs due to hyperemesis or other causes (level 3).86, 87, 88

53Furthermore, intravenous thiamine should be given at a minimum dose of 100 mg daily with intravenous vitamin B complex if oral supplementation is not possible due to the severity of vomiting (level 3).86, 87, 88 Further supplementation in regards to vitamin B12, iron, vitamin D, calcium, vitamin A, and vitamin K should be provided as in the preconception period (level 4).

54Our recommendations for preconception nutritional supplementation generally agree with the British Obesity and Metabolic Surgery Society (BOMSS) and the American Society of Metabolic and Bariatric Surgeons (ASMBS) recommendations63, 84 and represent the commonly agreed standard of care with regards to micronutrient replacement.

55Limited data are available on breastfeeding after BS. In longitudinal studies, the composition of breastmilk from women after BS was found to be largely comparable with women without prior BS (level 2++).89, 90 Gimenes et al91 found children born to mothers who had undergone BS and who were breastfed for at least 6 months to have lower fat mass and lower glucose levels, possibly protecting them from the development of obesity later in life. These authors therefore recommend breastfeeding in these women for at least 6 months in accordance to the general WHO guidelines (level 2+).92 Case reports have demonstrated adverse maternal and/or neonatal outcomes due to micronutrient deficiencies during lactation (level 3).93, 94, 95 Therefore, we advise supporting women wishing to breastfeed after BS (level 2+) and suggest that their nutritional status is closely monitored during lactation with additional supplements to those routinely advised after BS prescribed when necessary (level 3).

56Most types of BS have been found to double the risk of fetal growth restriction (FGR) and SGA infants in comparison with BMI‐matched women96 and women with obesity.97 This risk is higher with procedures that potentially further induce malabsorption (such as RYGB), when compared with procedures such as AGB or SG (level 2+).96, 98 Studies suggest that it would seem preferable for women of reproductive age to consider more restrictive procedures to limit this risk. AGB is however also associated with lower birth weight when the band remains inflated during pregnancy (level 2++).99 Ultrasound monitoring of fetal growth should be offered to all women with a history of BS (level 2++). We recommend monthly screening from viability, especially in the presence of additional risk factors (eg, smokers, low GWG, teenagers) (level 4).

57It is still unclear whether BS increases the risk for congenital malformations in the offspring as strong epidemiological data are lacking.33 Several case reports and case studies have reported on the association between nutritional deficiencies in the mother and congenital anomalies in the offspring (level 3).83, 100, 101, 102, 103, 104 We therefore suggest an additional detailed anomaly scan during the late first or second trimester, especially in women with nutritional deficiencies (level 3), and sonographic follow‐up of fetal growth during the third trimester (level 2++).

58Weight regain following BS is a known problem in a substantial number of patients.105, 106, 107 It is therefore important to avoid excessive GWG and postpartum weight retention in women after BS. On the other hand, insufficient GWG increases the risk for FGR and low birth weight.108 So far, no specific guidelines for GWG during pregnancy in postbariatric women are available and few studies have focussed on the subject.

59Overall, women with a history of BS gain less weight during pregnancy compared with women without prior BS, especially during the third trimester (level 2++).27, 109, 110, 111, 112, 113 Women who conceive within 18 months after surgery also appear to have less GWG in comparison with those who conceive after this period (level 2+).27 Sheiner et al114 compared GWG between different types of surgery and found a reduced GWG for vertical banded gastroplasty and silastic ring vertical gastroplasty when compared with RYGB, and higher GWG for AGB compared with all other forms of BS (level 2+).

60Studies correlating GWG and pregnancy outcome are scarce. Ducarme et al111 reported a significant reduction in both low birth weight (<10% centile) and macrosomia (>90% centile) after AGB compared with controls with obesity, despite lower mean GWG. In a small retrospective cohort, Santulli et al115 reported no clear relation between birth weight and GWG in women after RYGB (level 2−). Stentebjerg et al27 explored differences in outcome between women who gained appropriate, inadequate, or excessive weight according to the Institute of Medicine (IOM) guidelines for pregnant women.116 GWG exceeding the guidelines increased the risk for preeclampsia and low Apgar scores at 1 minute (level 2+). Women with GWG below the guidelines delivered the smallest children. Lapolla et al112 found a similar trend towards smaller children if GWG was below the guidelines. As pregnancy does not appear to affect long‐term weight in women with a history of BS (level 2+)25, 26 and in view of the strong correlation between insufficient GWG, adverse neonatal outcomes, and increased risk of low birth weight in the general population, we advise women with a history of BS to adhere to the IOM guidelines (level 2+).

61In women with AGB, evidence regarding band management and weight gain during pregnancy is also limited. Active band management appears to facilitate adherence to the IOM guidelines and was not associated with low birth weight (level 2++).26, 99, 109, 117 In contrast, band deflation was associated with macrosomia (level 3).117

62We recommend health professionals caring for women after BS to measure BMI and monitor GWG in order to advise regarding adequate GWG relating to their prepregnancy BMI in accordance to the IOM guidelines (level 2+). If GWG is excessive, women should be assessed for complications (level 2+). In the case of insufficient GWG, diet should be revised and fetal growth carefully monitored (level 4).

63Currently, there are no specific guidelines on screening and treatment for diabetes during pregnancy in women after BS. The risk of developing type 2 diabetes (T2DM) and GDM is reduced in women after BS when compared with women without BS matched for their preoperative BMI.118 In contrast, women who have undergone BS are often still affected by obesity or overweight and remain at higher risk for T2DM and GDM than women with a healthy weight without BS.96, 119 Undiagnosed diabetes in pregnancy results in an increased risk for adverse outcomes including fetal anomalies.120

64Women who are planning to become pregnant post‐BS should be screened for preexisting diabetes in the prepregnancy period, so that it can be identified and treated prior to conception (level 4). During pregnancy, women with a history of BS should routinely be screened for GDM (level 4).121, 122 Patients with other risk factors for developing GDM should be offered early screening according to local policies to exclude preexisting diabetes. This is best performed using fasting plasma glucose (FPG) or Hba1c (level 4). As data on cut‐off values during pregnancies after bariatric surgery are lacking, we recommended using the guideline from the American Diabetes Association (ADA).123 As such, the diagnosis of T2DM is made if HbA1c and/or FPG is greater than or equal to 6.5% and greater than or equal to 7.0 mmol/L, respectively. Care should be taken when using HbA1c as it is less sensitive to screen for T2DM and GDM using this method when compared with FPG. In addition, the HAPO study showed that associations with adverse outcomes were significantly stronger with glucose measures than with Hba1c.124 However, this is offset by the test's greater practicality as it can be used in the nonfasting state, and the wider application of a more convenient test may increase the number of diagnoses made.

65Oral glucose tolerance testing (OGTT) is appropriate for women with AGB and can be used to screen for GDM between 24 and 28 weeks (level 4).122 However, given the physiological changes associated with RYGB, SG, and BPD, there are valid concerns with regards to the tolerability (dumping) and accuracy of OGTT in these women (level 2−).121, 122, 125 Studies have suggested that using either a seven‐point capillary blood glucose (CBG) profile or continuous glucose monitoring (CGM) or for 1 week between 24 and 28 weeks is the most appropriate method for GDM screening in these women (level 4). However, appropriate threshold values for random capillary glucose thresholds need yet to be defined in the post‐BS population.

66In the absence of specific outcome data for the post‐BS population, it seems reasonable to aim for the same targets as used in the general population with GDM according to NICE126 or according to local policies, that is maintaining capillary blood glucose concentrations below 5.3 mmol/L fasting, 7.8 mmol/L 1 hour after eating, and 6.4 mmol/L 2 hours after eating, if these goals can be achieved without hypoglycaemia (level 4). In women with a history of T2DM that is in remission postoperatively, additional value may be gained from screening with fasting glucose or HbA1c at booking and in the second trimester (level 4).121 Screening in the third trimester should also be considered if there is a clinical suspicion of the interval development of diabetes (such as accelerated fetal growth indices).

67If the diagnosis of GDM is made, it should be treated according to local policies (level 4). In general, this consists of lifestyle interventions first. If glycaemic targets are not met after 1 to 2 weeks, pharmacological treatment should be considered.127

68BS is associated with an increased risk for mental health problems and substance abuse.128, 129, 130 Data on mental health and substance abuse during pregnancies after BS are very limited. Higher anxiety rates during pregnancy are reported, without significant increase in depression rates (level 2+).131 We found no data on postpartum depression following BS. Guelinckx et al60 reported on maternal smoking during the first trimester of pregnancy in post‐BS women. Overall smoking rate was 24%, without a clear relation to the type of procedure. Smoking prevalence was comparable with the general nonpregnant female population, but much higher than in the general pregnant population in the same region (6%). No studies were found reporting on alcohol or other substance abuse during pregnancies after BS. As such, we recommend health providers to screen for anxiety and other mental health disorders prior and during pregnancy, and follow‐up should be offered when necessary (level 2+). Smoking cessation and alcohol use should be discussed when necessary as per general prepregnancy guidance (level 2−).

69Evidence for two common surgical complications during pregnancy was found: internal herniation following RYGB and gastric band slippage following AGB. With regards to internal herniation, an incidence of 8% has been reported during pregnancies after RYGB.132 Upper abdominal pain complicates 46% of such pregnancies, and internal herniation is diagnosed in 32.8% of these cases (level 3).133 Women reporting abdominal pain had an increased risk of preterm birth and significantly lower birth weight compared with women without abdominal pain, suggesting that severe abdominal pain and abdominal surgery may induce uterine contractions (level 3).133 Repeat internal herniation can occur in the same pregnancy even after previous closure of mesenteric defects (level 3). In a review of 22 cases of internal herniation during pregnancy after BS, all patients presented with abdominal pain and half of patients presented with nausea and/or vomiting. The most common location of the hernia was Petersen's space (45.5%), and there was a high incidence of maternal and fetal death in this case series (9% and 13.6%, respectively) (level 2−).134 A systematic review reported that all maternal and perinatal deaths in pregnancies complicated by internal herniation after RYGB occurred in women treated later than 48 hours after symptom onset (level 2++).135

70We recommend that all women with RYGB should be advised about the risks and symptoms of internal herniation and should seek appropriate medical assistance without delay. Care providers should be advised that any pregnant women with a history of RYGB that presents with abdominal pain should be assumed to have a small bowel obstruction due to internal herniation until proven otherwise (level 4)136 and that imaging techniques and operative intervention, often performed with reluctance in pregnant women, should not be delayed (level 2++).

71Gastric band slippage may be increased during pregnancy due to vomiting and increased intraabdominal pressure. One study reported an incidence of 12% during pregnancy compared with 3% to 5% in the general AGB population (level 3).137 A shorter time interval between AGB and pregnancy was associated with a higher rate of primary band revisions after pregnancy (level 2+).138 Patients should be counselled on the risk and symptoms of band slip during pregnancy and in the postpartum period (level 4).

72The recommendations issued in this review are based on a systematic research of the literature by a multidisciplinary group of international experts. The group has identified areas for which the level of evidence and therefore the quality of the recommendations is largely based on expert opinion. It is felt by the group that following areas need further robust investigation with regard to women and children's health in pregnancy following BS: Contraceptive counselling, safety, efficacy, and useTiming of pregnancyGestational weight gain recommendationsNutrition during pregnancyOptimal macronutrient monitoring and substitution/supplementation such as protein intake, including management of supplementation and when parental nutrition should be consideredOptimal micronutrient monitoring and substitutionPrevention and treatment of dumping and PPHMonitoring of fetal growthScreening and treatment for GDMScreening and treatment of surgical complicationsMental health and substance abuse

73Contraceptive counselling, safety, efficacy, and use

74Timing of pregnancy

75Gestational weight gain recommendations

76Nutrition during pregnancy

77Optimal macronutrient monitoring and substitution/supplementation such as protein intake, including management of supplementation and when parental nutrition should be considered

78Optimal micronutrient monitoring and substitution

79Prevention and treatment of dumping and PPH

80Monitoring of fetal growth

81Screening and treatment for GDM

82Screening and treatment of surgical complications

83Mental health and substance abuse

84This review summarizes current recommendations on the periconception, antenatal, and postnatal care of women following BS. Recommendations on the care of these patients are summarized in Table 3 and presented in a print‐friendly format for practical use in the clinical setting (Figure 1). Our work highlights the paucity of studies on the optimal care for this growing group of women and identifies research gaps in this field. The publication of these guidelines will be the first step in a research collaboration which will address these unanswered questions.

85The Institute of Advanced Studies (IAS) provided financial support of the international workshop organized at the University of Surrey, UK. RD received a fundamental clinical investigatorship from FWO Flanders (1803311N). The authors declare no conflict of interest.