1Singh S Sedgh G, Hussain R. Unintended pregnancy: worldwide levels, trends, and outcomes. Stud Fam Plann, 2010, 41 (4) : 241-250.
2Qian x, Tang S, Garner E Unintended pregnancy and induced abortion among unmarried women in China: a systematic review. BMC Health Serv Res ,2004,4( 1 ) : 1.
3Cheng Y,Gno X, Li Y, et al. Repeat induced abortions and contraceptive practices among unmarried young women seeking an abortion in China. Int J Gynaecol Obstet, 2004, 87 (2) : 199-202.
4Zhang K, Li D, Li H, et al. Changing sexual attitudes and behaviour in China: implications for the spread of HIV and other sexually transmitted diseases. AIDS Care, 1999, 11 ( 5 ) : 581-589.
5Ma Q, Ono-Kihara M, Cong L, et al. Early initiation of sexual activity: a risk factor for sexually transmitted diseases, HIV infection, and unwanted pregnancy among university students in China. BMC Public Health, 2009,9:111.