16744
However , several studies have raised concerns regarding pharmacokinetic alterations in pregnancy , particularly in the third trimester , which results in suboptimal drug concentrations and a theoretically higher risk of virologic failure and perinatal transmission .
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Please list all entity words in the text that fit the category.Output format is "type1: word1; type2: word2". 
Option: Chemical 
Text: {0} 
Answer:
 None