Wikstrom, who had six birdies and three bogeys in heavy rain at the Kingston Heath course, was confined to indoor practice in Finland before the tournament.
'I haven't played outside for a month until I came here,' Wikstrom said. 'On a couple of holes we got pretty hard rain. It's OK, I come from Scandinavia.'
The rain eased in the afternoon, when New Zealand's Sarah Nicholson, South Korea's Park Hee-young and Australia's Katherine Hull all shot 71s.
Defending champion Karrie Webb had a 1-under 72 and was a stroke further back in a group of six.
'It was not the nice, sunny day you'd like to play for your first round of the year but I'll take 1-under,' Webb said. 'I am pretty happy with the way things turned out.'
England's Laura Davies (74) was among a group of 12 at 1-over.
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