Common medical issues in the antepartum period Medication use in pregnancy

Throughout the world, medical practitioners became alerted to the potential dangers of medication use in pregnancy with the occurrence of congenital limb defects associated with thalidomide use. Following these events, physicians became much more cautious in using any medication in pregnancy. Several largescale studies were conducted in the USA by the Collaborative Perinatal Project and the CDC that collected information on drug exposures and outcomes for a large number of medications in many thousands of women. More recently, a number of drug registries have been established to study anti-epileptic drugs (AEDs), asthma medications, and antidepressants in pregnancy. Ongoing medication surveillance and information services provide both public educational service and data collection, such as the Motherisk program in Toronto. Studies of medication use during pregnancy demonstrate that between 20 and 50% of women receive medication other than vitamins and minerals in pregnancy. 20 The most frequently used medications include antibiotics and anti-nausea medications. The appropriate use of medication in pregnancy hinges on several important clinical principles.
Firstly, practitioners must determine that treatment of an illness or symptoms of an illness is beneficial to the mother and beneficial to the fetus, or that the risk to the fetus is justified by the potential benefits of treating the mother.
Secondly, accurate information must be available to assess the risk of congenital malformation or other negative impact upon the fetus or pregnancy. Experts vary in recommendations about medication. Some conservative viewpoints express concern, not only about teratogenesis, but also about the risk of long-term subtle effects on neurodevelopment.21 Caution must be balanced, however, with the risk of untreated disease or the intolerability of untreated symptoms. Some medications do not appear to cause malformations, but may be associated with other poor outcome, such as restricted fetal growth, presumably caused by their effects on the uteroplacental circulation. Some medications are risky only at certain periods of time within the pregnancy, such as the effect of non-steroidal anti-inflammatory medications on fetal renal function or the risk of kernicterus caused by bilirubin displacement from albumin-binding sites by sulfonamides. Specific knowledge of the mechanism and timing of risk may enhance the clinician’s effective utilization of medications in pregnancy. Two systems of classification currently exist for medication use during pregnancy.
Table 9.3 depicts the Food and Drug Administration’s (FDA) classification system. This system has been criticized for providing insufficient information about the risks of medications in pregnancy. The requirements to achieve a category A rating are stringent, difficult to achieve, and extremely costly to pharmaceutical industries;22 many medications undergoing FDA approval are not submitted for consideration of category A status because of financial issues. A number of medications that are currently classified as “B” are poorly studied in human pregnancy (e.g. leukotriene receptor antagonists) and should be used only if treatment benefits are clear. Other medications currently classified as category C are frequently used in pregnancy and have good safety records.
The Swedish catalogue of registered pharmaceutical specialties (FASS) uses a different system to categorize medication, included in Table 9.4.
The TERIS protocol for cataloguing teratological information utilizes all available sources of information and assigns ratings of teratogenic risk of “none,” “minimal,” “small,” “moderate,” “high,” and “undetermined.” A 1990 overview of this resource demonstrated that approximately half of the commonly prescribed medications had insufficient information to assess teratogenic risk. Of the drugs that could be rated, over 90% were rated as minimal risk or less.23
Important initiatives underway include drug registries regarding medication for common chronic illness, such as epilepsy and asthma. It is to be hoped that these projects will provide better information for clinicians about the treatment of medical illness in pregnancy. Between 20 and 50% of women receive medication other than vitamins and minerals during pregnancy.

Posted in: Health,Medical care and pregnancy