If you are planning to become pregnant, you should not take simvastatin. It is thought to have the potential to cause birth defects.
I personally wouldn't recommend taking a statin unless you really need it for high lipids. Statins have risks of serious side effects, like liver or muscle damage. I have been on statins for a year and I have to have my liver function checked regularly. All of those risks are very small, but in my opinion I would want to see if they posed the same risks to people without high lipids. I don't know if there are any studies of Zocor or Vytorin (another lipid-lowering drug that contains simvastatin) in people without high lipids.
Here is a page about the possible risks of Zocor:
http://www.druginfonet.com/pi_mfr/pp...ocor/zocor.htm