3Santelli J, Roehat R, Kendra HT, et al. The measurement and meaning of unintended pregnancy. Perspeet Sex Reproduet Health, 2003,35(2) :94-101.
4Barrett G,Wellings K. What is a 'planned' pregnancy? empirical data from a British study. Social Sol Med, 2002,55 (4) :545-557.
5Hellerstedt WL,Pirie PL, Harry A Lando, et al. Differences in preconeeptional and prenatal behaviors in women with intended and unintended pregnancies. Am J Pub Heal, 1998,88 (4) : 663-666.
6Diaz H,Werler MM, Walker AM, et al. Folie acid antagonists during pregnaney and the risk of birth defeets. N Engl J Med, 2000,343(22) :1608-1614.
7Honein MA, Paulozzi LJ, Watkins ML. Maternal smoking and birth defects:validity of birth certificate date for effect estimation. Pub Heal Rep,2001,116(4) :327-335.
8Green-Raleigh K, Lawrence JM, Chen HC, et al. Pregnancy planning status and health behaviors among nonpregnant women in a ealifornia managed health care organization. Perspect Sex Reproduet Health,2005,37(4) : 179-183.
9Henshaw SK. Unintended pregnancy in the United States. Fam Plann Perspect, 1998,30 ( 1 ) : 24-29,46.
10Foster DG, Bley J, Mikanda J, et al. Contraceptive use and risk of unintended pregnancy in California. Contraception, 2004,70 ( 1 ) : 31-39.
