No they are implants. When she crossed over into pop and became a media superstar in the late 1970s, she was significantly overweight, although her small frame and costuming made her appear average in size everywhere except the breasts, which were very large and quickly became the target of late-night talk show host jokes. At the time, whenever asked if her breasts were real, she said they were real. In the mid-1980s, she lost a considerable amount of weight. In interviews afterward, she avoided answering whether her breasts had been augmented, referring to any procedure as only a "lift." In 2002, however, she admitted for the first time in separate interviews with The Irish Independent and The Daily Mirror that after the weight loss in the 1980s, she lost a great deal of breast size and subsequently obtained breast implants to bring them back to a similar size as she had prior to the weight loss. Since then, she has made ample jokes in media interviews about their not being natural.
She even once joked by saying "Yep they are mine! Bought and paid for!".