Most bisexual porn is made by small production companies rather than the major studios. In POV porn, the shooting style is generally similar to gonzo pornography, with the person receiving sexual gratification holding the camera him or herself—aiming it down at the actress or actor who is performing the sex act. Double penetration of the vagina, anus and mouth, can involve: Simultaneous penetration of the anus by two penises or other objects. Works in this genre may explore philosophical, political or social issues. In 1988, a sex tape caused significant damage to Rob Lowe career. Medical pornography involves sexualized hentai movies medical, often fake, including gynecological pelvic examinations, rectal examinations, and pelvic or gynecological ultrasounds. The naked appearance of actress Demi Moore in the advanced stage of pregnancy on the cover of Vanity Fair magazine in 1991 marked the beginning of a period which has since seen pregnancy presented by celebrities as a glamorous state of living, while also creating a market for photographers to produce images of pregnant mothers, and for fashion stylists to introduce pregnancy styling to their business. Older names for a pornographic film include stag film, and gaysex blue movie. A woman can use a secondary vibrator, between the dildo and her genitals, to get pleasure from pegging. It is geared towards heterosexual men, who most typically define a threesome as such. The first explicit pegging scene is believed to have been in the 1975 pornographic film The Opening of Misty Beethoven. Since mammary intercourse is a non-penetrative sex act, the risk of passing a sexually transmitted infection that requires direct contact between the mucous membranes and pre-ejaculate or semen is greatly reduced. Tentacle erotica can be consensual, but frequently momporn contains elements of non-consensual sex. Group sex pornography features at least two men and two women , usually more, who all perform sex acts on each other. Biological anthropologist Helen B.