Final answer:
The nurse practitioner should inform the patient to wait 4 weeks before trying to conceive after receiving the varicella vaccination to ensure safety for the potential fetus.
Step-by-step explanation:
The nurse practitioner should advise the 29-year-old female patient that she needs to wait 4 weeks before conception after receiving the varicella vaccination. This precautionary waiting period is recommended to avoid any potential risk to the fetus, as the varicella vaccine contains live, attenuated virus. It is crucial for women of childbearing age to ensure their vaccinations are up-to-date to protect themselves and their future offspring from vaccine-preventable diseases.