Welcome to HCM,
This is not safe way as even one drop enter into the vagina may produce pregnancy
Natural safe way is having sex on safe period i.e. roughly first and last week of menstrual period provided period of your wife is regular.
Go for using Condom which is safe.
Insertion of IUCD ( intra uterine contraceptive device ) is equally safe.
Best safe measure is going for Oral contraceptive pills
Ok and bye.