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. The purpose of this kind of agreement is primarily to encourage discussion and negotiation in advance, and then to document that understanding for the benefit of all parties. The loose and direct camera work often includes tight shots of the genitalia, unlike some traditional porn. These are often gay twinks fake. Threesome or 3some pornography features one man and two women . The most common male masturbation technique is simply to hold the penis with a loose fist and then to move the hand up and down the shaft. The Girls Gone Wild momsex series is one example. The cover is open while the submissive lies down on his back and places his head in the box. Medical pornography involves sexualized medical, often fake, including gynecological pelvic examinations, rectal examinations, and pelvic or gynecological ultrasounds. Such works have also often been subject to censorship and other legal restraints to publication, display or possession. The introduction of the home video and Internet saw a boom in the worldwide porn industry that generates billions of dollars annually. To avoid soreness from this resulting friction, some may prefer to use a personal lubricant, masturbation cream or saliva during masturbation. By comparison, gonzo pornography puts the camera right into the action, often with one or more of the participants both filming and performing sexual acts, without the usual separation between camera and performers seen in conventional porn and cinema. A woman can use a secondary vibrator, between the dildo and her genitals, to get pleasure from pegging. The precise definition of roles and self-identification is a common subject of debate, reflection, hentai movies and discussion within the community.