Management and Outcomes of Pregnancy following Bariatric Surgery

| May 5, 2008 | 1 Comment

by Jane A. Alston and Giselle G. Hamad, MD, FACS

Ms. Alston is from University of Pittsburgh School of Medicine. Dr. Hamad is with University of Pittsburgh Department of Surgery, Division of Minimally Invasive Bariatric and General Surgery.

In recent decades, obesity has become an epidemic, particularly among women of childbearing age in America. Of all patients undergoing any form of bariatric surgery, females represent 72 percent, and the vast majority of them are of reproductive age.1 As such, obstetricians are seeing an increasing number of female patients who have undergone bariatric surgery, and may require guidance from bariatric surgeons to become more familiar with the unique issues involved in the patients’ care. A study of obesity in 2004 demonstrated that 33.2 percent of women 20 years of age or older were obese and 6.9 percent were morbidly obese in the United States.2 Many obstetric and gynecologic complications commonly arise in this patient population. First, obesity promotes infertility, and second, obese patients who do become pregnant are at a higher risk for complications such as preeclampsia, pregnancy associated hypertension, venous thromboembolism, gestational diabetes, shoulder dystocia, and fetal macrosomia, among many others.3,4 Fortunately, bariatric surgery gives morbidly obese women an opportunity for improved health and fertility.

Timing of Conception
Because of the dramatic weight loss following bariatric surgery, it is generally recommended that women avoid pregnancy until after the first 12 to 18 months, or until their weight stabilizes. This is a unique dilemma in the care of these women, since weight loss often results in regulation of the ovulatory cycle and increased fertility. Deitel, et al., found that of the 32 women (29%) who had infertility problems before undergoing bariatric surgery for morbid obesity, nine conceived postoperatively.5 In addition, there is considerable debate as to the ideal birth control method for these patients. Oral contraceptive pills are poorly absorbed following gastric bypass (GBP), and the transdermal contraceptive patch has decreased efficacy in patients greater than 90kg.6,7 Patel, et al., recommend the use of either intramuscular depomedroxyprogesterone injections or intrauterine devices in conjunction with regular condom use, although it should be noted that 1 in 3 women on depomedroxyprogesterone experience weight gain.8

Nutritional Deficiencies
The primary nutritional concerns include iron, vitamin B12, folate, and calcium deficiencies in post-GBP pregnancies.9 While there is a concern about postoperative protein deficiency, no data exist to demonstrate that pregnant post-GBP patients require any more protein than the 60gm recommended for either pregnant or post-GBP patients independently.10 Patel, et al., empirically began protein supplementation in patients who became pregnant within the first year of surgery, and recommend oral protein supplementation in patients experiencing weight loss or weight plateau during pregnancy or to those whose fetal growth falls below the 50th percentile.8,10

Folate deficiency is of even greater concern because neural tube defects (NTDs) can have devastating effects and can only be corrected surgically if the fetus survives. Haddow, et al., published data on three cases of NTDs among 35 pregnancies following GBP.11 Knudson, et al., debated the significance of this case report, given that pregnancies occurred 6 to 8 years postoperatively; of the three women reported, none were taking prenatal vitamins, two had low serum B12 levels, and only one had borderline low folate.12 Furthermore, in their own review of 77 post-GBP pregnancies, no NTDs were observed. While some contend that GBP patients require additional folate supplementation to decrease risk, there is little data to support this. At a minimum, these women should receive the 400mg of folic acid recommended for all women of reproductive age to reduce the risk of NTD. In addition, we now know that obese women are at significantly greater risk for NTDs when compared to women of normal body mass index (BMI). Their risk of NTD increases proportionately with maternal weight greater 70kg regardless of folic acid intake.13 Therefore, the perceived risks of NTD among post-GBP pregnancies must be weighed against the risks of obesity in pregnancy without surgery.

Gurewitsch, et al., published a case of a GBP patient presenting at six weeks gestation with significant iron and cobalamin deficiencies.14 Although the cobalamin deficiency was responsive to treatment, the iron deficiency did not respond to oral supplements and eventually required transfusion to correct the anemia. Post-GBP patients, particularly those trying to become pregnant, should be supplemented with 40 to 65mg of iron in the form of either ferrous sulfate or ferrous fumarate, which may have fewer gastrointestinal side effects than ferrous sulfate.15 Calcium should be supplemented in the form of 1,200 to 1,500mg of calcium citrate daily, and B12 may be given orally daily or intramuscularly monthly at doses between 350 and 1000mg.16,17

Recommendations that advise patients to delay pregnancy are primarily based on the concern for micronutrient and vitamin deficiencies; however, recent data comparing patients who became pregnant within their first postoperative year with those who delayed pregnancy until after one year revealed no significant episodes of malnutrition, adverse fetal outcomes, or pregnancy complications. Dao, et al., studied 34 patients, 21 who became pregnant within the first year and 13 who became pregnant after one year.18 Antenatal complications and fetal outcomes, including type of delivery, fetal birth weight, major complications (preeclampsia and miscarriages), and minor outcomes (preterm labor, hypertension, cholelithiasis, and iron deficiency) were comparable between the two groups. It is worth mentioning that there were significant variations in maternal weight between the two groups. The groups had similar average BMIs at the time of surgery, but the early group had a BMI of 35 at the onset of pregnancy, whereas the later group had a BMI of 28. As a result, the early group gained an average of only four pounds during pregnancy and the late group gained 34 pounds.

Prenatal Screening Tests in Bariatric Surgical Patients
Screening for gestational diabetes is recommended in all pregnancies; however, post-GBP patients may be unable to tolerate either the classic 50-gram glucose challenge or the 100-gram oral glucose tolerance test due to dumping syndrome. Dumping syndrome occurs because rapid gastric emptying of hyperosmolar contents directly into the small bowel after GBP leads to fluid shifts into the bowel lumen, resulting in distention.19 In early dumping syndrome, patients present with abdominal cramping, bloating, nausea, vomiting, and diarrhea. Later, a subsequent release of excessive insulin causes subsequent hypoglycemia. Therefore, late dumping syndrome patients present with tachycardia, palpitations, agitation, and diaphoresis.

Landsberger, et al., suggested using modified glucose testing. They recommend obtaining a fasting blood glucose level and a two-hour postprandial level after consuming the most carbohydrate-loaded breakfast the patient can tolerate.20 If fasting and two-hour postprandial glucose levels are less than 95mg/dL and 120mg/dL respectively, they are considered normal. Landsberger also recommends following hemoglobin, hematocrit, serum iron, ferritin, erythrocyte folate, methylmalonic acid, albumin, prealbumin, serum calcium, phosphate, and 25-hydroxy vitamin D levels. They assert that erythrocyte folate is a better indicator of true deficiency, whereas serum folate merely reflects recent oral intake, and that methylmalonic acid is more sensitive in detecting vitamin B12 deficiency. Finally, Wax, et al., recommend that second trimester maternal serum a-fetoprotein and ultrasound screening be offered, even if current data reflects that the risk of NTDs is theoretical.21

Decreased Antenatal Morbidity after Bariatric Surgery
Up to this point, we have focused primarily on the risks of pregnancy following bariatric surgery; however, it is important to weigh those risks against the risks of pregnancy among obese patients. Skull, et al., identified women who had had successful laparoscopic adjustable gastric banding (LAGB) surgery and compared their postoperative pregnancies to their preoperative pregnancies.22 Of the 44 women (80 pregnancies), the postoperative pregnancies had a significantly lower mean maternal weight gain (3.7kg vs. 15.6kg in the non-LAGB group), and significantly fewer total number of complications (including diabetes, pregnancy-induced hypertension, preeclampsia, and eclampsia). Fetal weights were not significantly different, nor were there differences in delivery methods between the two groups. Patel, et al., reported similar reductions when comparing their Roux-en-Y GBP patients against both non-obese and obese women.8 Ducarme, et al., reported that in their patient population, the incidence of preeclampsia, gestational diabetes mellitus, low birth weight, and fetal macrosomia were each significantly lower in the LAGB group when compared to obese controls.23 Dixon, et al., compared first post-LAGB pregnancy patient data with data from their penultimate pre-LAGB pregnancy and a matched obese cohort.24 Post-LAGB pregnancies had a significantly lower incidence of pregnancy-induced hypertension and preeclampsia compared to the other two groups. In addition, they had significantly fewer instances of gestational diabetes when compared to the matched obese cohort.

Obstetrical Outcomes following Bariatric Surgery

Post-bariatric surgery patients have been shown to have higher occurrences of cesarean section. Sheiner, et al., compared 298 deliveries after bariatric surgery to 158,912 control deliveries that occurred during the same time period.25 He found a significant association between bariatric surgery and cesarean section, even when controlled for possible confounders (including previous cesarean delivery, obesity, fertility treatments, premature rupture of membranes, labor induction, diabetes mellitus, hypertensive disorders, and fetal macrosomia). Patients who had undergone bariatric surgery had a 25.2-percent rate of cesarean compared with 12.2 percent in the control group (p<.001). This study included patients who had undergone any type of bariatric procedure (open or laparoscopic; restrictive or malabsorptive) and found no difference in outcomes between these groups. Associations were also found between bariatric surgery and macrosomia, premature rupture of membranes, and induction of labor; however, it should be noted that Sheiner’s control group had significantly lower BMIs than his post-bariatric surgery group (p<.001). Although a significant association between bariatric surgery and cesarean has been found, there is no physiologic explanation for this link; therefore, some postulate that it is merely due to provider bias.

Roux-en-Y gastric bypass. GBP may lead to serious gastrointestinal complications during pregnancy, most notably, internal hernia resulting in small bowel obstruction. Pregnant patients may be at increased risk for hernia due to increased intra-abdominal pressure.26 A review of the literature reveals eight such cases.27-33 Five resolved after surgical intervention with reduction and repair of the internal hernia or small bowel resection (some also involved cesarean section with or without bilateral tubal ligation). One case was further complicated by maternal deep vein thrombosis and endometritis, another resulted in maternal death, and the last resulted in both maternal and fetal death despite emergency cesarean section to deliver the 31-week-old fetus. Finally, Wax, et al., described a case complicated by intussusception, which was subsequently reduced with no further complication to mother or fetus.34 The interval between surgery and conception in these patients ranged from four months to two years.

The important lesson to be learned from these cases is that the presentations of many of these patients were subtle and were easily confused with more common, benign obstetrical complaints such as “morning sickness,” Braxton-Hicks contractions, hyperemesis, and gastroesophageal reflux. In the case report of the mother and fetus who died, physicians mistook her initial presentation for pancreatitis. Many patients present with nausea, decreased appetite, and mild, intermittent, abdominal pain; few complain of vomiting. Connolly, et al., conducted a study of the causes of intestinal obstruction during pregnancy and found that the majority (55%) were due to adhesions from previous surgery.35 Pregnant patients are most susceptible to obstruction at three separate times during the pregnancy: mid-pregnancy when the uterus becomes an abdominal organ, third trimester when the fetal head descends, and immediately postpartum when there is an acute change in the size of the uterus.36 It is important for bariatric specialists, patients, and their obstetricians to be aware of these possible complications and the timeline in which they are most likely to occur, particularly because the presentation can be subtle and delaying the diagnosis of internal hernia and bowel ischemia may be fatal.

Laparoscopic adjustable gastric banding. LAGB offers additional flexibility in managing weight gain during pregnancy. Some bariatric practices choose to be most conservative, deflating all of their bands when their patients are first diagnosed with pregnancy and experiencing nausea. Weiss, et al., deflated the bands in all seven pregnancies (average BMI of 34.8) to relieve nausea and vomiting; however, this did not improve symptoms. Of the five successful births, patients gained an average weight gain of 5.9kg.37 Dixon, et al., removed fluid from all bands at the onset of pregnancy (n=22) and then added fluid as need to manage weight gain at 14 weeks. Bands were deflated at 36 weeks per protocol, and this strategy resulted in an average weight gain of 8.3kg.38 They also reported three patients who had their bands emptied and did not undergo further management until after delivery: Two of those three pregnancies resulted in excessive weight gain (19kg and 26kg). Skull, et al., set a goal for minimal maternal weight gain and of the 49 LAGB pregnancies, adjusted only 18 percent (primarily band deflation or complete emptying, although one patient had fluid added to the band).22 They did not discuss in detail the reasons for adjustment, but their management resulted in an average weight gain of only 3.7kg, with no difference in the neonatal complication rate when compared to the control group.

The most common complications following LAGB were band leakage and band migration. Each of these studies included at least one instance of each. None of these complications resulted in adverse outcomes to either mother or fetus, although they did require surgical correction. There are also case reports of more serious complications in pregnancy following LAGB. Skull, et al., reported two cases of gastric prolapse that required laparotomy and band removal; however, both patients had peri-gastric band positioning, which is associated with higher risk of gastric prolapse than the pars flaccida technique.22,39 Dixon reported one woman who suffered hyperemesis; her band had not been deflated until late in the pregnancy because of distance.38 She was induced and the band was deflated after delivery due to unresolved vomiting. Another woman developed cholelithiasis complicated by pancreatitis during her third trimester. Her band was completely deflated after the diagnosis of biliary colic, and despite overall weight loss during pregnancy, she had an uncomplicated delivery followed by an uncomplicated cholecystectomy at six weeks post-partum. Finally, Erez, et al., reported a case in which a woman presented at 35 weeks with vomiting and abdominal pain.40 She was induced, but two hours later developed an acute abdomen with signs of fetal distress and required laparotomy with cesarean delivery for a perforated ulcer at the band site. Both mother and fetus survived.

Summary of Recommendations
There are many complex issues involved in the care of obstetric patients who have undergone bariatric surgery. Therefore, it is crucial that a multidisciplinary approach is undertaken, with open communication between patient, bariatric surgeon, obstetrician, and dietitian. Optimally, a discussion about the patient’s desire for future pregnancy should occur before the decision is made to undergo bariatric surgery. This ensures that patients have proper contraception in place during their period of rapid weight loss to decrease the risk of unintended pregnancy. Once pregnant, a dietitian should be involved to monitor for and treat deficiencies throughout the course of the pregnancy. Special obstetric screening may be advised, including modified glucose testing, second trimester maternal serum a-fetoprotein, monthly ultrasound to monitor appropriate growth, and anatomic ultrasound. In mid- to late pregnancy, obstetricians and bariatric surgeons must be aware of serious complications such as internal hernia, even for fairly common complaints such as nausea and vomiting.

While there are clearly distinct advantages to bariatric surgery, particularly when compared to the risks of obesity in pregnancy, much remains unknown. This is likely to change as the number of reproductive-aged women undergoing bariatric procedures increases. Larger studies are needed to develop definitive protocols for contraception, prenatal screening, prenatal band management, and delivery guidelines for these patients, but the preceding is a collection of current knowledge from which we can expound.

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