Chapter 17: Principles of Drug Therapy in Pregnancy and Lactation

LEARNING OBJECTIVES

1. Discuss the principle of drug transfer across the placenta to the fetus.

2. Describe the principles of drug transfer into breast milk and subsequent factors affecting drug transfer to the infant.

3. Compare and contrast the classification of drugs during pregnancy and lactation.

4. Understand how to use resources for information regarding drug effects during pregnancy and lactation.

INTRODUCTION

The use of medications in pregnant and breastfeeding (or breast-pumping) women has risen significantly over the last few decades. It is estimated that between 40% and 90% of pregnant women take at least one medication during pregnancy.^1,2 The increased frequency of medications used during pregnancy is likely the result of more extensive clinical experience and the perception of a clearer safety profile for many therapeutics.

Although the majority of these medications are prescribed by the patient’s health care provider, many mothers still use over-the-counter medications, often without seeking medical advice. Even more often, women may consume some medication before the realization that they are pregnant.³ Most recent information available from the Pregnancy Risk Assessment Monitoring System (PRAMS) from 2009 indicates that only 18.4% received preconception care and 29.7% took daily folic acid supplementation during the month prior to conception.⁴ A similar 2004 PRAMS assessment revealed that 30% of women reported seeking advice from a health care provider regarding preparation for a healthy pregnancy and infant.⁵

Information from one population-based study conducted during 1998 to 2002 found that although the prevalence of medication use decreased from 72% before pregnancy to 56% during pregnancy, it returned to 78% in the postpartum period.⁶ The most commonly used medications during pregnancy in this population included antibiotics (75%), oral contraceptives (45%), and nonsteroidal anti-inflammatory drugs (NSAIDs; 17%). In the postpartum period, the most commonly used medications were NSAIDs (56%), oral contraceptives (53%), and antidepressants (13%). Another study has indicated that antiemetics, tranquilizers, antihistamines, and diuretics are additional frequently used medications during pregnancy.⁷

An assessment of prescription drug use in Hawaii from 2009 to 2011 surveyed women with recent live births and found that 14.2% reported prescription drug use before pregnancy and 17.6% reported prescription drug use during pregnancy.⁸ The most commonly reported types of prescription medications used during pregnancy in this report were anti-infectives, pain relievers, and gastrointestinal drugs. Of those women who reported prescription use during pregnancy and attending prenatal care, 10.3% reported that they did not receive counseling regarding safe medication use during their prenatal care.

Ultimately, the use of medications during pregnancy and lactation involves a level of complexity not usually encountered by most health care providers when prescribing drugs. Contrary to the most typical situation, in which a health care provider’s risk benefit analysis involves only the patient, pharmacotherapeutics involving pregnant and lactating women must take into account both the patient (ie, the mother) and the ...