Ireland's Leona Maguire birdied three of her last four holes to take a one-stroke second-round lead on Friday in the Women's PGA Championship at rain-soaked Baltusrol.

Maguire, who started the day three off the pace, shook off a slow start that saw her par her first five holes before a bogey at the 15th. She responded with a birdie at the 17th and grabbed another at the fourth before a bogey at the fifth.

Then she cantered home with birdies at the sixth, seventh and ninth to card a three-under 68.

Her five-under total of 137 put her one clear of a group of three on 138: England's Mel Reid, Norway's Celine Borge and China's Lin Xiyu.

Reid carded a 67, Borge signed for a 69 and Lin shot an even par 71.

It was a further stroke back to Australia's Minjee Lee, who posted a 67, and overnight leader Lee-Anne Pace of South Africa, who posted a two-over 73.

"Really happy with how I played today," Maguire said. "Weather was a little bit trickier today, especially on the back nine when that rain came in."

"Didn't really hole any putts on the front side, but nice to get those three birdies coming in," added Maguire, who said a solid hybrid into the ninth gave her a comfortable seven-footer uphill putt to finish.

Maguire arrived in Springfield, New Jersey, riding the momentum of her second LPGA title at the Meijer Classic on Sunday.

Chasing a first major, however, requires a different mindset, she said.

"This is uncharted territory for me. Whatever happens this week, I'm sure I'll learn a lot, and just sort of taking it one day at a time," she said.

"I think this golf course demands that. I think you can't think more than one shot ahead, let alone a hole or a round ahead."

Maguire's European Solheim Cup teammate Reid was delighted to hit 18 greens in regulation on what she called a "beast of a golf course."

"The rough is really obviously thick," Reid said. "It's obviously a bit wet. I feel like that's OK for me because I'm one of the stronger players. I'm not really too scared about hitting it in the rough, so I feel like it's kind of freed my driver up."

Lin said she found the conditions even more challenging than Thursday's. She offset an opening bogey at the 10th with a birdie at 11 and followed a bogey at 15 with an eagle at the 18th.

"I've been trying to stay patient," Lin said. "I didn't really get angry with any of the bogeys I made, but then 18th hole I finally hit the fairway, so I was like, there's a good chance, and I hit that really good three-wood in the rain, and then it went up to like maybe 12-footer. When I made the putt, I was pretty pumped."