Northwestern attained the No. 1 ranking with its win over Penn, coupled with Penn State's triple overtime win over then-No. 1 Princeton.
The Lions were down and out early, as the Wildcats jumped out to a 6-0 lead with just less than 10 minutes remaining in the first half, before a goal by Penn State junior Shari Maslin ended the shutout bid.
When Penn State failed to capitalize on any momentum gained by the score, Northwestern re-established control with two quick goals. The Lions didn't get on the board again until a free position goal by junior Lauren Bryan with 43 seconds left in the first half.
A slightly more successful second half saw the Lions net four goals, but Northwestern added six for the 14-6 final score. Maslin and freshman Jessi Lieb led Penn State scorers with two goals apiece in the losing effort.
Penn State's all-time career saves leader Lee Tortorelli had seven saves on 29 shots, as she constantly faced pressure from the Wildcats offense.
"Their attack is the best attack we've seen this year," Penn State coach Suzanne Isidor said. "They do a great job of moving the ball and they've got some great shooters. Our defense and Tort were under a lot of pressure all game."
Northwestern held advantages in every major statistical category. The Wildcats won 13-of-22 draws, controlled 13 groundballs to Penn State's eight, and outshot the Lions 29-20.
"It's just one of those games where everything that could go wrong went wrong and it was not the best day to do have that happen," Isidor said. "We needed to play one of our best games to beat Northwestern and we played one of our worst."
Northwestern improved to 13-0 on the season with the win.
The Lions have until Friday to correct their problems and lick their wounds as they host No. 20 Ohio State at 7 p.m. in the first of two games on the weekend. Sunday, Ohio comes in to Happy Valley for an afternoon contest.
Keeping the loss in perspective Isidor said that her Lions have gone 2-1 against No. 1-ranked teams and Northwestern has yet to fall this year.
"We were disappointed we didn't play better, but they're a team that has the opportunity to win the national championship," Isidor said.