Starting in 1996, Alexa Internet has been donating their crawl data to the Internet Archive. Flowing in every day, these data are added to the Wayback Machine after an embargo period.
Prematurity Statistics The Perinatal Data Center at the March of Dimes has a number of statistical resources regarding preterm labor and birth and other perinatal topics:
The Prematurity Profile: A Statistical Overview for the United States presents a snapshot of data illustrating different aspects of prematurity, including the number of preterm births, the increase in preterm births and associated risk factors.
State data regarding prematurity can be found at PeriStats, your online source for perinatal statistics from the March of Dimes.