Treating constipation during pregnancy

Abstract

Question Many of my patients experience constipation during pregnancy, even after increasing dietary fibre and fluids. Are there any safe treatments I can recommend to them?

Answer Although the recommended first-line therapy for constipation includes increasing fibre, fluids, and exercise, these are sometimes ineffective. Therefore, laxatives such as bulk-forming agents, lubricant laxatives, stool softeners, osmotic laxatives, and stimulant laxatives might be considered. Although few of the various types of laxatives have been assessed for safety in pregnancy, they have minimal systemic absorption. Therefore, they are not expected to be associated with an increased risk of congenital anomalies. However, it is recommended that osmotic and stimulant laxatives be used only in the short term or occasionally to avoid dehydration or electrolyte imbalances in pregnant women.

It has been estimated that approximately 11% to 38% of pregnant women experience constipation,¹ which is generally described as infrequent bowel movements or difficult evacuation.² Pregnancy predisposes women to developing constipation owing to physiologic and anatomic changes in the gastrointestinal tract. For instance, rising progesterone levels during pregnancy and reduced motilin hormone levels lead to increases in bowel transit time.^2,3 Also, there is increased water absorption from the intestines, which causes stool to dry out. Decreased maternal activity and increased vitamin supplementation (eg, iron and calcium) can further contribute to constipation.³ Later in pregnancy, an enlarging uterus might slow onward movement of feces.⁴ Constipation can result in serious complications such as fecal impaction, but such complications are rare. It is important to note that constipation negatively affects patients’ daily lives and is second only to nausea as the most common gastrointestinal complaint in pregnancy.^2,4

Treatment

Many patients find relief from constipation with an increase in dietary fibre and fluids, as well as daily exercise. Probiotics that alter the colonic flora might also improve bowel function.³ If these are ineffective, laxatives are the second line of therapy (Table 1).^2,5,6 In general, there are insufficient data on the use of laxatives in pregnancy; however, limited studies have been performed for specific laxatives, and the safety of others can be inferred from information about their systemic absorption (Table 2).^7–16

Table 1.

Types of laxatives

TREATMENT	MECHANISM OF ACTION	EXAMPLES
Bulk-forming agents	Luminal water binding increases stool’s bulk, making it easier to pass5	Psyllium, bran
Stool softeners	Stimulates net secretion of water, sodium, chloride, and potassium and inhibits net absorption of glucose and bicarbonate in the jejunum6	Docusate sodium or calcium
Lubricant laxatives	Decreases surface tension of bowel’s liquid contents so that more liquid remains in the stool, thereby facilitating evacuation and decreasing straining2	Mineral oil
Osmotic laxatives	Increases osmolar tension, resulting in increased water collection, distention, peristalsis, and evacuation2	Salts (eg, sodium chloride, potassium chloride), magnesium sulfate or citrate, lactulose, sorbitol, polyethylene glycol
Stimulant laxatives	Acts locally to stimulate colonic motility and decrease water absorption from large intestine5	Bisacodyl, senna

Data from West et al,² Tack et al,⁵ and Moriarty et al.⁶

Table 2.

Studies examining safety in pregnancy and systemic absorption of commonly used laxatives

DRUG	TYPE OF STUDY	DETAILS	OUTCOMES
Psyllium	Surveillance	100 > N < 199 during first trimester	No increased risk of malformations7
Docusate sodium	Prospective	N = 116 anytime during pregnancy	No increased risk of malformations8
	Surveillance	N = 473 during first trimester	No increased risk of malformations (1/473 = 0.2%)7
	Surveillance	N = 319 during first trimester	No increased risk of malformations (3/319 = 0.9%)9
	Surveillance	N = 232 during first trimester	No increased risk of malformations (9/232 = 3.9%)10
Lactulose	Pharmacokinetics	N = 6 adults given lactulose	Systemic bioavailability < 3%11
Polyethylene glycol	Pharmacokinetics	N = 11 adults given polyethylene glycol	Not absorbed12
Bisacodyl	Pharmacokinetics	N = 12 adults given oral and rectal bisacodyl	Minimal absorption13
	Pharmacokinetics	N = 16 adults given bisacodyl suppository	Systemic bioavailability < 5%14
Senna	Case-control	N = 506 cases (260 during first trimester)	No increased risk of malformations (OR 0.8; 95% CI 0.4–1.4) or adverse pregnancy outcomes15
	Pharmacokinetics	N = 937 control (500 during first trimester); N = 10 adults given senna	Systemic bioavailability < 5%16

OR—odds ratio.

Data from Jick et al,⁷ Heinonen et al,⁸ Aselton et al,⁹ Briggs et al,¹⁰ Carulli et al,¹¹ Wilkinson,¹² Roth and Beschke,¹³ Flig et al,¹⁴ Acs et al,¹⁵ and Krumbiegel and Schulz.¹⁶

Bulk-forming agents

Bulk-forming agents are not absorbed⁴ or associated with increased risk of malformations⁷; therefore, they are considered safe for long-term use during pregnancy. However, they are not always effective and might be associated with unpleasant side effects such as gas, bloating, and cramping.⁴

Stool softeners

Docusate sodium has not been associated with adverse effects in pregnancy in a number of studies, and it is thus also considered safe to use.^7–10 There is one case report of maternal chronic use of docusate sodium throughout pregnancy, which was associated with symptomatic hypomagnesemia in the neonate.¹⁷

Lubricant laxatives

Mineral oil is poorly absorbed from the gastrointestinal tract¹⁸ and does not appear to be associated with adverse effects.¹⁹ There is controversy about whether prolonged use reduces the absorption of fat-soluble vitamins, although this appears to be a theoretical rather than actual risk.²⁰

Osmotic laxatives

Lactulose and polyethylene glycol are poorly absorbed systemically.^11,12 Their use has not been associated with adverse effects; however, individuals might experience side effects such as flatulence and bloating.³ Theoretically, prolonged use of osmotic laxatives might lead to electrolyte imbalances.³

Stimulant laxatives

Absorption of bisacodyl is minimal as it has poor bioavailability.^13,14 Senna does not appear to be associated with increased risk of malformations¹⁵ and is not readily absorbed systemically.¹⁶ However, women might experience unpleasant side effects such as abdominal cramps with the use of stimulant laxatives.² Similar to osmotic laxatives, prolonged use might theoretically lead to electrolyte imbalances.³

Conclusion

The first line of therapy for constipation includes increasing dietary fibre and water intake and moderate amounts of daily exercise.³ If these are ineffective, laxatives are the second line of therapy. Because most laxatives are not absorbed systemically, short-term use has not been, and is not expected to be, associated with an increased risk of malformations. However, as with the general population, it is recommended that osmotic and stimulant laxatives be used only in the short term or occasionally to avoid dehydration or electrolyte imbalances and the theoretical risk of “cathartic colon.”²¹

MOTHERISK

Motherisk questions are prepared by the Motherisk Team at the Hospital for Sick Children in Toronto, Ont. Ms Trottier and Dr Erebara are counselors and Ms Bozzo is Assistant Director of the Motherisk Program.

Do you have questions about the effects of drugs, chemicals, radiation, or infections in women who are pregnant or breastfeeding? We invite you to submit them to the Motherisk Program by fax at 416 813–7562; they will be addressed in future Motherisk Updates.

Published Motherisk Updates are available on the Canadian Family Physician website (www.cfp.ca) and also on the Motherisk website (www.motherisk.org).