I would have thought it depends on the audience you were hoping to attract and in which country, as well as whether the sexual act was gratuitous, or something done to put over an important point or theme in the novel. In my own novel,
Secrets From The Dust, there is a scene with an implied sexual assault of an under-aged girl. It is never seen, but when she leaves the abusers room, the reader knows what has taken place:
In a previous scene the reader is told that the abuser uses a baton that she carries like a man thing. Then later:
“All the other girls were in bed long before Lilly slithered into the dormitory as if she were stepping onto hot coals, sniffing back tears. She climbed with halting spasms into bed, and with each movement to get there she belched out a sharp moan. Margaret got up and crept to stoop by her bedside. “You alright, Lilly?” There was no response. The moonlight rested on Lilly’s face, which was ashen and vacant, and her red eyes were swollen with tears. Her two hands rested between her legs like a broken shield, guarding that place.”
The other day the BBC World Service reported about teen novels in Uganda, which are extremely sexually explicit. One deals with two twelve year old boys having sex with a girl and contracting aids. Another with a rape in a taxi cab. One mother explained that the reason she bought that type of book for her teenaged daughter was because it enabled them to discuss subjects that were important to her protection and that they would not otherwise discuss.
So it depends on your scene and its purpose, just don’t make it gratuitous is my opinion.