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The Society of Maternal-Fetal Medicine on managing pregnant patients who have had gastric banding or gastric bypass surgery.
A 31-year-old woman presents for a routine first prenatal appointment. She has had bariatric surgery.
The obstetrician should determine the type of weight loss surgery that was performed. Bariatric surgery can cause weight loss through intake restriction, food malabsorption, or a combination of these. The 2 most common bariatric procedures performed in the United States in reproductive-age women are Roux-en-Y gastric bypass (65%) and adjustable gastric banding (24%).1 Roux-en-Y gastric bypass restricts intake and food absorption, whereas adjustable gastric banding limits only food intake.
Other bariatric surgeries are performed but are much less common. Today, biliopancreatic diversion is rarely performed because it is associated with a higher mortality rate and more significant nutritional deficiencies.2,3 Vertical banded gastroplasty and sleeve gastrectomy are both restrictive surgeries.
Nutritional deficiencies are frequently encountered in patients who have undergone bariatric surgery and they can be amplified during pregnancy. Malabsorptive procedures are associated with more nutritional deficiencies than is restrictive surgery, as outlined in Table 1.3
Nonpregnant patients who have had bariatric surgery are commonly prescribed a variety of nutritional supplements because of nutritional deficiencies. Table 2 outlines examples of some of these routine supplements.
When a patient who has undergone bariatric surgery becomes pregnant, a detailed history should be obtained at the first prenatal visit. Patients with prior bariatric surgery may have unique nutritional deficiencies that are not routinely considered in healthy obstetric patients. These deficiencies may cause health problems. Persistent complaints such as muscle pain or cramps, easy bruising and/or skin and mucosal changes in a pregnant patient may be symptoms of vitamin or micronutrient deficiencies.4 These may be more relevant if the patient is still in the rapid-weight-loss phase following her bariatric surgery.
Current guidelines suggest checking serum levels of vitamin B12 and folate during pregnancy in women with prior bariatric surgery,5 along with a complete blood count, iron, ferritin, calcium, and vitamin D levels; measurement every trimester has been suggested.6 Longitudinal nutritional data are not available or limited, however, regarding vitamin supplementation and other supplementation during pregnancy in women who have had bariatric surgery. Therefore, the recommendations are based on expert opinion.
In patients who have had bariatric surgery, stomach pH is altered and the surface area for absorption decreases. These changes may warrant manipulation in the preparation, route, or dose of nutrient replacements. Liquid or chewable vitamins are better absorbed than tablets.7 Calcium carbonate depends on acid for absorption, whereas calcium citrate does not; therefore, calcium citrate is the recommended replacement.8 Administration of iron simultaneously with vitamin C improves iron absorption because the vitamin C helps to acidify the stomach. 9
Absorption of oral vitamin B12 depends on intrinsic factor produced by the parietal cells of the stomach, and production of intrinsic factor may be significantly altered when a part of the stomach is surgically removed. Therefore, even with adequate oral supplementation in a patient with malabsorptive surgery, a nutritional deficiency in vitamin B12 may not be corrected and intramuscular injections may be required.4 Because of reduced drug absorption, periodic monitoring of nutritional levels is suggested to ensure adequate replacement.
Some women with malabsorption resulting from bariatric surgery may have vitamin A deficiency. High levels of vitamin A intake have been associated with fetal anomalies.9 Currently human evidence is insufficient to establish a safe threshold for daily intake. The maximum amount of vitamin A recommended for pregnant women is 8000 to 11,000 IU per day or not more than 5000 IU in supplements.6,10
Bariatric surgery patients are at particular risk of anemia, which is also common during pregnancy. If common causes of anemia like iron deficiency, vitamin B12 or folate deficiency, and hemoglobinopathy are excluded, clinicians should consider less-common causes of nutritional anemia, such as copper deficiency.
Care should be taken when administering screening tests for gestational diabetes. In about 50% of patients who have Roux-en-Y gastric bypass, dumping syndrome can occur. It is characterized by symptoms including a shaky, sweaty, dizzy sensation accompanied by a rapid heart rate and, occasionally, by severe diarrhea.11 Alternative methods, such as home glucose monitoring or hemoglobin A1C measurement, may be considered.
Patients who undergo bariatric surgery, especially malabsorptive procedures, are at increased risk of nutritional deficiencies (Table 1). Pregnancy may make some of these nutritional deficiencies more severe by increasing demand or decreasing intake, especially if a patient has nausea and vomiting. The evidence for monitoring of nutritional deficiencies and for supplementation is insufficient to make any strong recommendation, and more research is needed. Patients should continue to receive monitoring and supplementation as needed, in collaboration with the bariatric surgery team and medical specialists, and the ob/gyn should remain vigilant for signs and symptoms of nutritional deficiencies. With careful monitoring, women with bariatric surgery are likely to have normal pregnancy outcomes.
Dr. Johnson is Professor, Department of Obstetrics and Gynecology, Medical University of South Carolina, North Charleston.
This opinion was developed by the Publications Committee of the Society for Maternal-Fetal Medicine with the assistance of Donna Johnson, MD, and was approved by the Executive Committee of the Society on August 7, 2013. Neither Dr. Johnson nor any member of the Publications Committee (see the list of 2013 members at www.smfm.org) has a conflict of interest to disclose with regard to the content of this article.
Disclaimer: The practice of medicine continues to evolve and individual circumstances will vary. Clinical practice also may vary. This opinion reflects information available at the time of acceptance for publication and is not designed nor intended to establish an exclusive standard of perinatal care. This publication is not expected to reflect the opinions of all members of the Society for Maternal-Fetal Medicine.
To download this patient education handout, go to http://contemporaryobgyn.net/pregnant_after_bariatic_surgery.pdf.
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