@article{Ventura2012,
author = {Ventura, S.J. and Curtin, S.C. and Abma, J.C. and Henshaw, S.K.},
title= {Estimated pregnancy rates and rates of pregnancy outcomes for the United States, 1990-2008},
year = {2012},
journal = {National Vital Statistics Reports},
volume = {60},
number = {7},
pages = {1--21},
}