Gastrointestinal (GI) disorders represent some of the most frequent complaints during pregnancy. Some women have GI disorders that are unique to pregnancy. Other pregnant patients present with chronic GI disorders that require special consideration during pregnancy. Understanding the presentation and prevalence of various GI disorders is necessary to optimize care for these patients. [1, 2] This article focuses on common GI symptoms during pregnancy and the common GI diseases that can be challenging to manage during pregnancy.
Nausea and Vomiting
Nausea, with or without vomiting, is common in early pregnancy, usually self-limiting [3, 4] and occurs in 50-90% of pregnancies, whereas vomiting is an associated complaint in 25-55% of pregnancies. Risk factors for nausea in pregnancy include youth, obesity, first pregnancy, and smoking. Nausea tends to recur in subsequent pregnancies, though it may be shorter in duration.
Nausea in pregnancy occurs in 91% of women in the first trimester, generally in the first 6 to 8 weeks. In its mild form, nausea is known as morning sickness. The pathophysiology of this condition is debatable but has been attributed to hormonal fluctuations, GI motility disorders, and psychosocial factors. Persistence of nausea and vomiting into the second or third semester should prompt a search for other causes.
Other causes of nausea in pregnancy include urinary tract infections, gastroenteritis, peptic ulcer disease, pancreatitis, biliary tract disease, hepatitis, appendicitis, adrenal insufficiency, and increased intracranial pressure. In later pregnancy, considerations also include hydramnios, preeclampsia, and onset of labor.
Management of symptoms
The severity of symptoms dictates the approach to therapy in a pregnant patient with nausea. Mild symptoms can be managed by reassurance, avoidance of precipitating factors, and changes in diet (eg, smaller, more frequent meals; increased carbohydrate intake; low fat intake).
For more severe and intractable symptoms, pharmacotherapy with antiemetics can be offered. Meclizine (class B) or promethazine (class C) can be used. Adverse effects to the human fetus have not been reported, but meclizine and promethazine are not recommended for routine use in pregnancy.
Metoclopramide (class B) can be used in pregnancy. It has not been shown to induce teratogenic effects, but it crosses the placenta and produces substantial fetal blood alcohol effects.
Data on the harmful fetal effects of other antiemetics (eg, prochlorperazine [class C], diphenhydramine [class C], trimethobenzamide) preclude their use in pregnancy. Pyridoxine (vitamin B-6) is an alternative therapeutic agent in patients with severe nausea or vomiting. 
The prognosis for the mother and child is generally good. In fact, women with mild nausea and vomiting in pregnancy have better pregnancy outcomes compared with women without these symptoms.
Hyperemesis gravidarum occurs in 3 to 10 cases per 1000 pregnancies and is characterized by intractable nausea and vomiting that occurs in early pregnancy, leading to fluid and electrolyte imbalances. [6, 7, 8] This condition may be considered to be at the severe end of the spectrum of nausea and vomiting in pregnancy, but the pathogenesis of hyperemesis gravidarum is poorly understood. Hormonal and psychologic factors may play a role. Risk factors associated with this condition include obesity, nulliparity, multiple gestations, and trophoblastic disease
Hyperemesis gravidarum occurs early in the first trimester, usually within weeks 4 through 10. Symptoms usually resolve by weeks 18 to 20. The symptoms of hyperemesis gravidarum include intractable vomiting; ptyalism; weight loss of >5% of body weight; possible malnutrition; abdominal pain (not common); possible ketosis, hypokalemia, and metabolic alkalosis; possible abnormal liver enzyme levels; and possible mild hyperthyroidism.
Management of metabolic imbalances, diet, and symptoms
Treatment of hyperemesis gravidarum focuses on replenishing fluids, electrolytes, vitamins, and minerals.  Thiamine supplementation is recommended for women who have had vomiting for longer than 3 weeks. It is important for the patient to avoid environmental triggers. In addition, patients should eat frequent, small, high-carbohydrate, low-fat meals to assist in managing this condition. Gut rest may be needed in some cases. Parenteral or enteral nutrition can be beneficial in some cases.
Antiemetics and pyridoxine can be used to alleviate nausea and vomiting. Corticosteroids have been tried in severe and refractory cases.
The prognosis with hyperemesis gravidarum is good. No differences in birth weight or birth defects have been observed in pregnancies affected by this condition.
Gastroesophageal Reflux Disease
Gastroesophageal reflux disease (GERD), generally known as heartburn, is common in pregnancy and is experienced by 45-80% of pregnant women [10, 11, 12, 13, 14, 15, 16, 17, 18] Fifty-two percent of pregnant women first experience GERD in their first trimester, 24-40% experience it in their second trimester, and 9% in their third trimester.
Both mechanical and intrinsic factors are involved in GERD. Abnormal esophageal motility, decreased lower esophageal sphincter (LES) pressure, [19, 20, 21, 22, 23, 24, 25] and increased gastric pressure contribute to GERD in pregnancy. Increased intra-abdominal pressure from the gravid uterus and displacement of the LES also contribute to GERD in pregnancy.
Pregnant women with GERD present similarly to individuals in the general population; heartburn and regurgitation are the cardinal symptoms. The diagnostic evaluation consists of a thorough patient history and physical examination; diagnostic studies are rarely needed. Endoscopy may be indicated in patients with complications of GERD, and 24-hour ambulatory pH studies can be useful in patients with atypical presentations (eg, cough, wheezing, sore throat) and refractory symptoms.
Lifestyle modifications and pharmacologic management
Lifestyle modifications are the first line of management in pregnant women with GERD. To reduce symptoms and increase comfort related to GERD, advise pregnant patients to elevate the head of the bed; avoid bending or stooping positions; eat small, frequent meals; and refrain from ingesting food (except liquids) within 3 hours of bedtime.
With regard to medications, antacids or sucralfate are safe in pregnancy, because they are not systemically absorbed. Note, however, that antacids may interfere with iron absorption.
Histamine 2 (H2) blockers are preferred over proton pump inhibitors (PPIs), because more data are available on the safety of H2-blocker use in pregnancy. However, a recent large cohort study found that exposure to PPIs in the first trimester of pregnancy was not associated with increased risk of birth defects.  Cimetidine, ranitidine, and famotidine can be used in pregnancy (class B drugs), but they can cross the placental barrier. Lansoprazole is the preferred proton pump inhibitor in pregnancy (class B).
The outcome for pregnant patients with GERD is good. However, this condition tends to recur with subsequent pregnancies.
Pregnancy is associated with an increased risk of gallstone formation, which in turn is an important cause of pancreatitis in pregnancy. Cholecystectomy is the second most common nonobstetric surgical procedure in pregnancy, exceeded only by appendectomy. 
The exact mechanism of gallstone formation in pregnancy is not known, but 31% of women develop biliary sludge during pregnancy, and 2% develop new gallstones. The risk for these conditions is highest in the second or third trimester and during the postpartum period. Possible contributing factors are an increased lithogenicity of bile, increased stasis of bile, and decreased gall bladder emptying.
Pregnant women with cholelithiasis may present with right upper quadrant or epigastric pain, fever, vomiting, jaundice, tenderness in the right upper quadrant that may be difficult to elicit because of an enlarged uterus, and/or pancreatitis. 
Medical and surgical management
Severe biliary colic can be managed conservatively with hydration, narcotics, antibiotics, and dietary modifications. Endoscopic retrograde cholangiopancreatography (ERCP) may be needed in cases of cholangitis, biliary obstruction, or pancreatitis.
Cholecystectomy is indicated in the presence of persistent or recurrent symptoms, significant nutritional compromise, and weight loss. This procedure is required in less than 0.1% of cases. The second trimester is the best period for surgery in affected pregnant women.
Peptic Ulcer Disease
Peptic ulcer disease (PUD) is uncommon during pregnancy, with a reported incidence rate of 0.005%, although this is probably underestimated. PUD is believed to improve during pregnancy as a result of decreased gastric acid secretion. Risk factors for PUD in pregnancy include smoking, alcoholism, stress, socioeconomic status, and previous history of PUD or Helicobacter pylori gastritis. Nonsteroidal medications are not a common risk factor for PUD in pregnancy.
The clinical features of this condition in pregnant women are similar to those in the nonpregnant state. Symptoms include dyspepsia, epigastric pain, nausea, vomiting, and heartburn. GI bleeding and perforation are rare complications of PUD in pregnancy. PUD does not cause increased maternal or fetal morbidity and mortality.
H2-receptor antagonists (eg, cimetidine, ranitidine, famotidine) are the first choices of treatment for peptic ulcer disease. Treatment for Helicobacter pylori gastritis should be initiated after the pregnancy and breastfeeding periods are complete, because some of the recommended medications are relatively contraindicated in pregnancy. Lansoprazole has been reported to be safe in pregnancy.
Diarrhea occurs in up to 34% of pregnant women, and its causes in pregnancy mirror those of the nonpregnant state, with the most common being infectious agents (eg, Salmonella, Shigella, and Campylobacter species; Escherichia coli; protozoans; viruses). Food poisoning, medications, and irritable bowel syndrome are other common causes. Exacerbations of inflammatory bowel disease can also occur in pregnancy.
Evaluation and management
Conduct a routine laboratory evaluation with stool studies for bacterial culture, ova, parasites, fecal leukocytes, and stool assay for Clostridium difficile infection. For persistent diarrhea, flexible sigmoidoscopy can be performed, as it is safe in pregnancy.
Conservative management is the mainstay of treatment for diarrhea in pregnancy. Administer fluid replacement, and administer medications to control the diarrhea, if needed. Nonsystemic medications should be tried first, and the underlying cause should be treated.
Treat patients with irritable bowel syndrome by instituting a high-fiber diet and administering stool-bulking agents. Avoid antidepressants. Anticholinergics/antispasmodics are not recommended.
The incidence rate of constipation in pregnancy is 11-38%. [29, 30] The etiology is multifactorial, with decreased small bowel motility, decreased motilin level, decreased colonic motility, increased absorption of water, and iron supplementation as possible contributory factors.
Evaluation and management
Extensive clinical evaluation is seldom warranted for constipation during pregnancy. The evaluation should include a careful history, including the presence of preexisting constipation, dietary habits, current medications, and the use of laxatives. Perform a digital rectal examination to exclude fecal impaction.
The results of blood studies can be useful to exclude hypothyroidism, diabetes mellitus, hypercalcemia, and hypokalemia as possible causes. If rectal bleeding is present, anoscopy or flexible sigmoidoscopy can be performed to exclude anorectal lesions. [31, 32, 33]
Conservative treatment is the mainstay of therapy for diarrhea in pregnancy and includes the following instituting dietary changes, increasing physical activity, performing Kegel exercises (may be useful), and using bulking agents (eg, psyllium, safe in pregnancy).
Few data are available on the safety and efficacy of medications in pregnancy. Stool softeners such as sodium docusate are probably safe. Stimulant laxatives are probably safe for intermittent use, but these agents should not be used regularly. Castor oil and mineral oil should not used in pregnancy.