Which factor does NOT affect drug clearance in pregnant women?

The factor that does not affect drug clearance in pregnant women is placental size. Drug clearance primarily depends on the physiological changes that occur during pregnancy, such as increased blood volume and changes in kidney function.

In pregnancy, blood volume significantly increases, which can enhance the distribution and clearance of certain medications. Alterations in kidney function, including increased glomerular filtration rate, also play a crucial role in the clearance of drugs.

While age can influence drug metabolism and clearance generally, its impact is less direct compared to the physiological changes specifically associated with pregnancy. The size of the placenta does not directly influence how drugs are cleared from the mother's system. Instead, it is more involved in the transport of substances between maternal and fetal circulation rather than affecting clearance rates directly.