SOUTHPORT, July 10, 2014 (AFP) - Windy conditions and deep rough set a stiff test but Uehara had five birdies in a four under par 68 and she led by one from American Mo Martin.
Uehara, a three-time winner on the Japanese Tour, made her only bogey at the long par four first, but she hit back with three birdies in the first half and more at the short 12th and long 18th.
Only nine players finished under par and the list included defending champion Stacy Lewis on 71.
But US Open champion Michelle Wie struggled from the tee and had to settle for a three over par 75.
Martin, who uses the long putter and is renowned with her accuracy from the tee, matched Uehara's haul of five birdies but dropped shots at the second and 12th.
Three players were on 70 -- Americans Morgan Pressel and Mina Harigae plus Australia's Sarah Kemp.
Now in her second season on the US-based LPGA Tour, pocket-sized Uehara has struggled to hit any sort of form this year and missed the cut in the first two majors.
"But today my putting was so good," said the world number 125 after holing a string of 15-foot efforts for the birdies.
"I come from Okinawa in Japan and so I am used to the wind. I'm so happy and excited to play well in a major and this is definitely my best round of the year. But there are another three days to go."
Lewis, the world number one and the winner at St Andrews last year, was happy to start with a number in red figures, even more so considering she was two over par after three holes.
"Anything under par is a good score today," she asserted. "The opening few holes are so tough and I bogeyed the first and third. But I knew I had to stay patient. The conditions were pretty horrible but I managed to make a few birdies "
Wie who finished third at Birkdale as a 15-year-old amateur in 2005, described her round as "a real battle".
After three bogeys and a solitary birdie at the second in the outward half she dropped further shots at the 14th and 16th before making a welcome four at the long 18th.
"I put myself in some pretty tough positions from the tee," she admitted.
"I was in too many pot bunkers and there was a lot of chipping out from the rough."
Leading first round scores Thursday at the Women's British Open USLPGA golf tournament (par 72):
68 - Ayako Uehara (JPN)
69 - Mo Martin (USA)
70 - Morgan Pressel (USA), Mina Harigae (USA), Sarah Kemp (AUS)
71 - Stacy Lewis (USA), Holly Clyburn (GBR), Ryu So Yeon (KOR), Amy Yang (KOR)
72 - Karrie Webb (AUS), Lexi Thompson (USA), Anna Nordqvist (SWE), Amelia Lewis (USA), Azahara Munoz (ESP), Park Inbee (KOR), Jessica Korda (USA), Suzann Pettersen (NOR), Ai Miyazato (JPN), Lydia Ko (NZL), Julieta Granada (PAR), Marina Alex (USA), Emma Talley (USA), Shin Jiyai (KOR)
73 - Gwladys Nocera (FRA), Charley Hull (GBR), Erina Hara (JPN), Feng Shanshan (CHN), Georgia Hall (GBR), Choi Chella (KOR), Lee Meena (KOR), Brittany Lang (USA), Shin Jenny (KOR), Jang Jeong (KOR), Pornaanong Phatlum (THA), Dori Carter (USA)