I think premarital sex can greatly effect a marriage, negatively.
Sex is important in a marriage, but it is not the only thing that holds a marriage together. Therefore, I don't agree that you have to be 'practiced' in order to have a healthy marriage.
The baggage a person can bring into marriage from having multiple partners before their monogamus marriage can be really detrimental to the health of a marriage.
Emotional, physical and mental baggage.
Sex for woman is based on trust, and security. If she has had various negative and emotional encounters with other men, she carries that into her marriage, affecting her willingness to "trust" her husband, and sex becomes a chore.
A man, on the other hand, has an ingrained mental image of his 1st sexual encounters. That first "hit", so to speak, is recorded into his mind and body, he spends the rest of his sexual life trying to fulfill that high again. This creates a unrealistic expectation on sex with his wife.
For example, if one night stands were a common sexual release for the man, then in marriage he sees sex as a non committal act, to release himself, therefore, disappointing his wife with his emotionless approach to intimacy.
So no, I do not think pre-marital sex is safe for the man or the woman, physically, mentally, or physically.