Micronutrients, Bariatric Surgery, and the Obstetrical Patient

February 25, 2014

Women who have had bariatric surgery require special care during pregnancy, particularly with assessment of micronutrient deficiencies and appropriate replacement. Here’s one ob/gyn’s approach.

With the rate of obesity growing as rapidly as our waist lines, it’s no surprise that a recent National Health and Nutrition Examination Survey determined that more than one third of all women are obese, half of all pregnant women are either overweight or obese, and 8% of reproductive-age women are morbidly obese.1

The World Health Organization categorizes obesity into the following 3 classes based on body mass index (BMI), measured in kg/m2:

▪ Class 1: BMI 30 - 34.99.
▪ Class 2: BMI 35 - 39.99.
▪ Class 3: BMI ≥ 40 (morbid obesity).

Overweight and obese obstetrical patients are at increased risk for a number of pregnancy complications, including gestational diabetes mellitus, hypertension, preeclampsia, cesarean delivery, venous thromboembolism, infection, fetal growth abnormalities, premature delivery, and possibly congenital anomalies. Therefore, patients who are overweight or obese should be counseled to lose weight before becoming pregnant. If they are unable to lose weight before becoming pregnant, managing weight gain during pregnancy becomes critical. Current recommendations for weight gain for singleton pregnancies are 15 to 25 lb for overweight women and no more than 11 to 20 lb for obese women.1

It is important to encourage weight loss in all of our patients who are overweight and obese. Some women are able to lose weight with diet and exercise, but many women struggle with weight loss or have trouble maintaining a weight loss. A subset of women has turned to bariatric surgery to help lose weight, and it is this group of women that I’d like to discuss.

When Lifestyle Changes Don’t Work

Bariatric surgery is an effective therapy for morbidly obese women both for weight loss and improvement of many of the comorbidities previously mentioned. Women accounted for 83% of all bariatric surgery procedures among 18- to 45-year-olds between 1998 and 2005.2 It is no wonder that we are seeing these women in our practices seeking obstetrical care.

The 2 most common bariatric surgical procedures performed in the United States on reproductive-age women are Roux-en-Y (65% of cases) and gastric adjustable banding (24% of cases).

The Roux-en-Y is considered to be both “restrictive and malabsorptive,” because it restricts the amount of food intake as well as the absorption of food since part of the intestinal tract is bypassed in this procedure. Because of the potential for malabsorption, up to 50% of these women may experience “dumping syndrome,” which manifests as shaking, sweating, dizziness, increased heart rate, and diarrhea.

The gastric banding procedure is referred to as “restrictive,” because it limits food intake and reduces the available surface area of the stomach.

Most bariatric surgeons recommend that women wait 12 to 18 months after bariatric surgery, which is considered the rapid weight-loss period, before attempting pregnancy (more on this study here).However, it has been reported that short-term perinatal outcomes of women who conceived during their first year after bariatric surgery (n=104) compared with those of women who conceived after their first year following surgery (n=385) were similar.4 In fact, there were no significant differences in birth weight, anemia, or preterm delivery between the two groups.

Vitamin BRed blood cell formation, neurological function, and DNA synthesis
FolateSynthesis of nucleic acids (DNA and RNA) and metabolism of amino acids
Vitamin BConversion of carbohydrates into energy
 Vitamin AImmune function, vision, reproduction, cellular communication
 Vitamin DCalcium absorption for strong bones
 Vitamin EAntioxidant properties
 Vitamin KBlood coagulation
CalciumBlood flow, muscle function, nerve transmission, cellular communication, hormonal secretion
IronOxygen transport

Keep in mind that bariatric surgery may be an independent risk factor for premature delivery, although a recent study showed that this increased risk was only found in women who also had an early pregnancy BMI of 30 or below.5 Interestingly, women with a BMI of 35 or greater had no increased risk of premature delivery (more on this study here.)

Current ACOG guidelines suggest that pregnant women with a history of bariatric surgery should be evaluated for nutritional deficiencies, and women who have had a gastric band procedure should also be monitored by their general surgeon throughout their pregnancy because band adjustments may be needed.1 ACOG also advises that bariatric surgery is not itself an indication for cesarean delivery, although many women who have had surgery for weight loss deliver via cesarean section.


Micronutrients: Screening and Managing Deficiencies

Micronutrient deficiencies in women who have had bariatric surgery continue to be a real concern, especially in women with a history of malabsorptive gastric surgery. The nutrients in which these women are most likely to have deficiencies are iron, vitamin B12, folate, vitamin D, and calcium, although deficiencies in other micronutrients are possible (Table 1).

To help ensure that both mother and baby are receiving adequate nutrition, it is recommended that these obstetrical patients receive the following screening tests each trimester: 

Calcium citrate1200 – 2000 mg/d
Folic acid400 µg/d
Vitamin B350 µg/d PO or 1000 µg IM monthly
Multivitamin1 daily
Vitamin D400 - 800 IU/d
Elemental iron40 - 65 mg/d

▪ Vitamin B12.
▪ Folate.
▪ CBC count.
▪ Iron/Ferritin.
▪ Calcium.
▪ Vitamin D.

Although rare, there have been reports that micronutrient deficiencies may have resulted in fetal complications, such as neural tube defects, decreased birth weight, and even rickets.6 In addition, maternal vitamin K deficiency in women who have had bariatric surgery has been linked to severe neonatal intracranial bleeding resulting in death of the newborn.7 Regular screening may avert these complications.

Care should be taken when performing the diabetic screen for gestational diabetes in Roux-en-Y patients because of the “dumping syndrome.” Therefore, a glycosylated hemoglobin test or a fasting blood sugar test may be better alternatives.

Which Supplements Work Best?

Chewable and liquid preparations of supplements will be better absorbed by patients who have had bariatric surgery. These patients tend to have decreased stomach acid, so calcium citrate, which does not rely on stomach acid for absorption, is a good option for a calcium supplement. Vitamin C improves stomach acid and should be given with iron supplements to improve absorption. With diminished gastric surface area, there is a diminution of intrinsic factor, which is essential for the absorption of vitamin B12. Therefore, intramuscular injections of vitamin B12 are often necessary to overcome this deficiency.

There is very little data on the ideal doses of micronutrient supplementation in pregnancy after bariatric surgery. The best we can do is extrapolating the suggested nutrient supplementation after bariatric surgery in the nonpregnant women to our pregnant patients (Table 2).

If our obstetrical patients who have had bariatric surgery are monitored and managed appropriately, we can expect a reduction in maternal morbidities associated with untreated obesity and also see a reduction in fetal complications associated with malabsorptive obesity treatments.


1. American College of Obstetricians and Gynecologists. Committee opinion no. 549: obesity in pregnancy. Obstet Gynecol. 2013;121:213-217.

2. Yermilov I, McGory ML, Shekelle PW, et al. Appropriateness criteria for bariatric surgery: beyond the NIH guidelines. 2009;17;1521-1527.

3. Khan R, Dawlatly B, Chappatte O. Pregnancy outcome following bariatric surgery. The Obstetrician & Gynaecologist. 2013;15:37-43.

4. Sheiner E, Edri A, Balaban E, et al. Pregnancy outcomes of patients who conceive during or after the first year following bariatric surgery. Am J Obstet Gynecol. 2011;204:50.e1-6. doi: 10.1016/j.ajog.2010.08.027.

5. Roos N, Neovius M, Cnattingius S, et al. Perinatal outcomes after bariatric surgery: nationwide population based matched cohort study. BMJ. 2013;347:f6460.

6. Hezelgrave NL, Oteng-Ntim E. Pregnancy after bariatric surgery. J Obes. 2011;2011:501939. doi: 10.1155/2011/501939.

7. Eerdekens A, Debeer A, Van Hoey G, et al. Maternal bariatric surgery: adverse outcomes in neonates. Eur J Pediatr. 2010;169(2):191-196.

8. Society for Maternal-Fetal Medicine, assisted by Johnson D. Assessing nutritional needs in pregnant patients with prior bariatric surgery. October 1, 2013. Available here.