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Upon completion of the chapter, the reader will be able to:
Explain the principles of embryology and teratology.
Identify known teratogens and drugs of concern during lactation.
Compare the main sources of drug information relevant to pregnancy and lactation.
Evaluate and communicate the risks of a drug when taken during pregnancy or lactation.
Apply a systematic approach to counseling on the use of drugs during pregnancy and lactation.
Recommend the appropriate dose of folic acid to prevent congenital anomalies.
Describe physiologic changes during pregnancy and their impact on pharmacokinetics.
Choose an appropriate treatment for common conditions in a pregnant or lactating woman.
This chapter will provide general principles to understand the scientific data on medication use during pregnancy and lactation, to choose appropriate treatment and adjust their dosage for a variety of conditions prevalent during pregnancy, and to counsel women in a helpful and supportive way.
EPIDEMIOLOGY AND ETIOLOGY
Background Risks of Anomalies in Pregnancy
Table 47–1 describes the baseline risks of congenital anomalies and some obstetrical complications. This information is essential to evaluate risks associated with medication use and to counsel pregnant women.
Table 47–1Occurrence of Some Obstetrical Complications and Risk of Congenital Anomalies in the General Population1-3 |Favorite Table|Download (.pdf) Table 47–1 Occurrence of Some Obstetrical Complications and Risk of Congenital Anomalies in the General Population1-3
| ||Risk of Occurrence in Population (%) |
|Spontaneous abortion/miscarriage (pregnancy loss that occurs after the pregnancy is known and before 20 weeks of GA; risk increases with higher maternal age) ||10–15 |
Congenital anomalies (percentage of live births):
|Preterm birth (< 37 completed weeks gestation)a ||9.6 |
|Low birth weight (< 2500 g)a ||8.0 |
Causes of Congenital Anomalies
Although the risk of drug-induced teratogenicity is of concern, the actual risk of birth defects from most drug exposures is small. Medications are associated with less than 1% of all congenital anomalies, although they may also interact with genetic factors.3,4 It is important to evaluate and optimize drug use in pregnant women and women planning a pregnancy.
Other causes of anomalies include genetic causes in 25% of cases (inherited disease, gene mutation, chromosomal disorder), maternal infections (1%), maternal conditions (1%–3%; eg, pregestational diabetes, obesity), multifactorial heredity (23%–50%), and unknown causes (34%–43%).3 Theoretical concerns regarding paternal exposure to genotoxic medication are reported, but currently no medication taken by a man has been proven teratogenic.4