Final answer:
The best nursing intervention would be to refer the client to a family planning clinic to receive appropriate counseling and guidance.
Step-by-step explanation:
The best nursing intervention at this time would be to refer the client to a family planning clinic. This is important because the client has multiple sex partners and is unsure of the identity of the baby's father. By referring her to a family planning clinic, she can receive appropriate counseling and guidance regarding contraception, sexually transmitted infections (STIs), and prenatal care.