@article{Ventura2004,
author = {Ventura, S. and Abma, J.C. and Mosher, W.D. and Henshaw, S.},
title= {Estimated pregnancy rates for the United States, 1990-2000: An update},
year = {2004},
journal = {National Vital Statistics Reports},
volume = {52},
number = {23},
pages = {1--9},
}