GI in Pregnancy: GI in Pregnancy: IBD and Gastric Bypass

0:00Welcome to Board Pearls. This is episode six of six, the last episode of the GI in Pregnancy chapter, in the Special Populations and Acute or Supportive Care module. This episode is inflammatory bowel disease in pregnancy, then pregnancy after gastric bypass. The first patient is a woman with Crohn disease who's planning a pregnancy. Her case shows why active disease is a greater danger than the drugs that control it, which drugs continue and which must stop months before conception, why one anti-tumor necrosis factor, TNF, drug crosses the placenta and another doesn't, how she's monitored and delivered, and what her baby's vaccines and her breastfeeding depend on. The second patient is a woman with severe abdominal pain late in pregnancy after a gastric bypass. Her case shows the surgical emergency that pain can mean, why the glucose tolerance test is avoided after bypass, and what her nutrition requires.

0:51Here's the first patient. A twenty-nine-year-old woman has ileocolonic Crohn disease, in remission for a year on adalimumab and azathioprine, with a normal fecal calprotectin. She wants to start trying for a baby and asks whether she should stop her medicines first to protect it.

1:07She has inflammatory bowel disease, IBD, in remission, and the answer to her question is no, because the principle behind every IBD decision in pregnancy is that active disease, not active medicine, is the greatest risk. A large prospective registry of completed pregnancies found no increase in congenital malformations, miscarriage, preterm birth, low birth weight, or infant infections with thiopurines, biologics, or the two combined, while higher disease activity at conception was linked to adverse outcomes. Active disease at conception roughly doubles the chance of active disease during pregnancy, in ulcerative colitis and in Crohn disease. Patients in remission at conception relapse during pregnancy in about fourteen percent. So keeping her in remission on the regimen that achieved it is safer than stopping her drugs for a fetal benefit no one has shown.

1:58Both of her drugs are on the list that continues through pregnancy. Mesalamine, oral and topical, sulfasalazine, azathioprine, 6-mercaptopurine, and corticosteroids are safe to continue. Azathioprine and 6-mercaptopurine are safe because they're prodrugs and the fetal liver lacks the enzymes that convert them to active metabolites, so the fetus sees little active drug, despite the old category D label. Sulfasalazine needs folic acid, two to three milligrams a day, because it blocks intestinal folate absorption and its sulfa component acts as a folate antagonist, raising the risk of neural tube defects. The anti-TNF agents, infliximab, adalimumab, golimumab, and certolizumab pegol, are safe to continue. Vedolizumab and ustekinumab have growing favorable data and are compatible with pregnancy, and vedolizumab's gut-selective action limits any systemic effect on the fetus. She continues adalimumab and azathioprine.

2:56Had she been on a different drug, the plan would start before conception. Methotrexate is absolutely contraindicated, because it inhibits dihydrofolate reductase and arrests DNA synthesis in dividing fetal tissue, making it teratogenic and abortifacient. It's stopped at least three to six months before conception, and the new regimen is confirmed to hold remission before she tries. Tofacitinib and upadacitinib are avoided, because broad Janus kinase, JAK, inhibition during organogenesis raises concern for fetal immune and blood cell development, with limited human data. Ozanimod, thalidomide, and rifaximin are avoided as well.

3:36Her adalimumab does reach her baby, and the mechanism explains how she's dosed. Antibodies of the immunoglobulin G, IgG, class, which include infliximab, adalimumab, and golimumab, are actively carried across the placenta in the late second and third trimesters. The neonatal Fc receptor, FcRn, on the syncytiotrophoblast binds the Fc region of IgG and transports it to the fetus. Transport speeds up after week twenty-two, so at term the baby's cord blood level can exceed the mother's. Certolizumab pegol is a PEGylated Fab-prime fragment with no Fc region, so FcRn can't bind it, and it doesn't cross the placenta in significant amounts. That's the distinction among the anti-TNF agents that's tested.

4:21So her biologic continues without interruption, with the option of timing the last dose six to ten weeks before her expected delivery, typically between thirty-two and thirty-eight weeks, so she delivers at a drug trough and her baby's cord level is lower. Her biologic resumes twenty-four hours after a vaginal delivery, or forty-eight hours after a cesarean, if there's no infection.

4:43Her disease activity is followed with tests that stay reliable in pregnancy. Fecal calprotectin remains a dependable marker of activity, while C-reactive protein, CRP, rises normally in pregnancy and can mislead. Clostridioides difficile is more common in pregnant patients with IBD and is tested for in any flare, because its symptoms overlap with active disease, so diarrhea at twenty weeks would bring a C. difficile test and a calprotectin. Ultrasound is safe, magnetic resonance, MR, enterography is preferred over computed tomography, CT, enterography, and gadolinium is avoided. Unsedated flexible sigmoidoscopy is safe, and colonoscopy with anesthesia and fetal monitoring is reserved for indications that can't wait until after delivery, ideally in the second trimester.

5:35Her pregnancy care adds two preventive measures. Low-dose aspirin, eighty-one to one hundred fifty milligrams daily, started by week eleven, is recommended in IBD pregnancy to prevent preeclampsia under the twenty twenty-five global consensus, so she starts it before week eleven. Venous thromboembolism prophylaxis is appropriate after delivery, because pregnancy and IBD are both prothrombotic.

5:59Her Crohn disease decides how she delivers only if it involves the perineum. Vaginal delivery is generally appropriate, and cesarean is indicated for active perianal disease, to avoid trauma to the sphincter or a fissure, or for a rectovaginal fistula. Without perianal disease, she can plan a vaginal delivery.

6:18Her adalimumab also affects her baby's first vaccines. Live vaccines are avoided in the first six to twelve months in infants exposed to biologics in utero, except after certolizumab, which didn't cross. The vaccine of concern is rotavirus, a live attenuated vaccine that could cause vaccine-strain disease while the infant's blood still holds maternal anti-TNF, which stays detectable for months. The twenty twenty-five consensus now allows rotavirus vaccine in infants of mothers on anti-TNF agents, interleukin-23 inhibitors, or vedolizumab, based on accumulating safety data, although many practices remain conservative. Measles, mumps, and rubella, MMR, and varicella vaccines at one year are safe, because drug levels are negligible by then. Her discharge summary names her adalimumab so her baby's pediatrician can plan.

7:10She can breastfeed on her regimen, because breastfeeding depends on molecule size. Mesalamine, thiopurines, and biologics continue, because large molecules pass minimally into milk and are broken down by the infant's stomach acid and proteases. Tofacitinib and methotrexate aren't used during breastfeeding, because small molecules cross into milk readily and could immunosuppress the infant.

7:35Now the second patient. A thirty-four-year-old woman had a Roux-en-Y gastric bypass three years ago and is thirty weeks pregnant. Her team avoided a glucose tolerance test earlier in pregnancy. Tonight she has sudden severe abdominal pain, mostly right upper quadrant, with vomiting, and she isn't in labor.

7:54Her pain is an internal hernia until proven otherwise, the surgical emergency to exclude in pregnancy after Roux-en-Y. The operation leaves gaps in the mesentery: Petersen space behind the Roux limb, the mesenteric defect at the jejunojejunostomy, and the transverse mesocolon defect if the limb was brought up behind the colon. Late in pregnancy, the enlarging uterus displaces bowel and changes intra-abdominal pressure, letting bowel herniate through those gaps, and incarcerated bowel can become necrotic within hours. The catastrophic error is calling her pain labor or hyperemesis. She gets a CT with shielding and prompt surgical exploration, because maternal deaths have followed a missed hernia.

8:37A marginal ulcer is also on her list. Ulcers at the gastrojejunal anastomosis are driven by smoking, nonsteroidal anti-inflammatory drugs, NSAIDs, and Helicobacter pylori, acting on jejunal mucosa that isn't adapted to acid. NSAIDs are avoided after Roux-en-Y for that reason, and an ulcer is treated with a proton pump inhibitor, PPI, and reversal of the risk factors. Her vomiting tonight also puts her at risk of thiamine deficiency, so she's given thiamine, as episode one explains.

9:09Her bypass explains why her team avoided the glucose tolerance test. The standard seventy-five or one-hundred-gram oral glucose tolerance test for gestational diabetes is avoided after Roux-en-Y, because without a pylorus to meter carbohydrate into the small bowel, the rapid sugar load causes dumping. Early dumping brings fluid shifts, hypotension, palpitations, and nausea, and late dumping brings reactive hyperinsulinemic hypoglycemia one to three hours later, which makes the test both uncomfortable and impossible to interpret. Fasting glucose with home glucose monitoring is used instead.

9:45Her timing and nutrition were planned around the same anatomy. Conception is delayed twelve to twenty-four months after bariatric surgery, because caloric restriction during the rapid weight-loss phase raises the risk of low birth weight and growth restriction, and nutritional repletion isn't complete. Roux-en-Y causes malabsorption of vitamin B12, iron, folate, calcium, vitamin D, and the fat-soluble vitamins, A, D, E, and K, because it bypasses the duodenum and proximal jejunum, where iron and calcium absorption peak, and because the small pouch exposes little food to intrinsic factor, limiting B12 absorption. Thiamine becomes deficient when vomiting occurs. Sleeve gastrectomy causes less malabsorption but still impairs B12 absorption, through loss of parietal cells, and thiamine with vomiting.

10:38So supplementation with monitoring of micronutrient levels is mandatory in pregnancy after either operation, and it continues through breastfeeding, because the same malabsorption applies, with the infant's B12, vitamin D, and calcium monitored.

10:54Here are the traps the boards set in these patients. Stopping IBD therapy to protect the pregnancy. Conceiving with active disease. Continuing methotrexate, or stopping it less than three months before conception. Using JAK inhibitors or ozanimod in pregnancy. Forgetting folic acid with sulfasalazine. Saying certolizumab crosses the placenta like the other anti-TNF agents. Monitoring with CRP instead of calprotectin. Giving live vaccines by reflex to an infant exposed to biologics. Choosing cesarean without perianal disease. Using a glucose tolerance test after gastric bypass. Conceiving within a year of bariatric surgery. And calling severe abdominal pain after gastric bypass labor.

11:39So, start to finish. IBD is kept in remission through pregnancy, because active disease harms pregnancy more than the drugs do. Mesalamine, thiopurines, anti-TNF agents, vedolizumab, and ustekinumab continue. Methotrexate stops at least three months before conception, and JAK inhibitors and ozanimod are avoided. Anti-TNF IgG antibodies cross the placenta late in pregnancy, while certolizumab doesn't. Activity is monitored with calprotectin rather than CRP, low-dose aspirin starts by week eleven, live vaccines are delayed in biologic-exposed infants, with rotavirus now permitted by recent consensus, and cesarean is reserved for active perianal disease or a rectovaginal fistula.

12:22After bariatric surgery, pregnancy waits twelve to twenty-four months, micronutrients are supplemented throughout, and gestational diabetes is screened with glucose monitoring rather than a tolerance test. Severe abdominal pain in pregnancy after gastric bypass is an internal hernia until proven otherwise, and it needs CT and early surgery.

12:42That completes chapter thirty-five. Chapter thirty-six is hereditary gastrointestinal cancer syndromes.

12:49For the full chapter, the practice vignettes, and the topic-tagged question bank, head to board pearls dot com. You'll find the rest of the series on Apple Podcasts, Spotify, or wherever you listen to podcasts. That brings us to the end of episode six of six of chapter thirty-five, and I'll see you in the next one.