New Zealand shares fell ahead of an interest rate announcement, with Fisher & Paykel Healthcare Corp, Summerset and Xero moving lower.

The S&P/NZX 50 Index dropped 45.3 points, or 0.7 per cent, to 6,750.41. Within the index, 32 stocks fell, 10 rose and seven were unchanged. Turnover was $223.7 million.

"We've had a couple of weak days. We have definitely come off the boil after a pretty strong run," said Mark Lister, head of private wealth research at Craigs Investment Partners.

The Reserve Bank's OCR update tomorrow has kept investors nervous, he said, with the US Federal Reserve and the Bank of Japan also due to make announcements.


"Markets have no idea what the Reserve Bank's going to do. They're quite split on whether they'll cut or hold fire, so the fact that there's a lot of uncertainty about the approach they'll take is probably weighing," Lister said. "Whenever it's a tough one to call, markets get a little bit nervous. People are going to be a little bit gun-shy until they get clarity."

F&P Healthcare fell furthest, down 3.3 per cent to $9.13. The breathing device manufacturer has high exposure to the New Zealand dollar's movements against the US dollar, with the US its biggest market.

"The Kiwi dollar has come off its highs but is still up pretty strongly against the US dollar," Lister said. "FPH coming off a bit is probably related to a stronger currency, and the shares have had a good run."

In addition, F&P Healthcare's ASX-listed competitor ResMed announced its quarterly results, which Lister said had disappointed the market with margins lower than expected.

Summerset Group dropped 3 per cent to $4.51, Xero fell 2.9 per cent to $16.50, and Air New Zealand shed 2.4 per cent to $2.64. Orion Health rose 2 per cent to $4.18. The health systems software company announced a contract with a Canadian province, enabling healthcare providers to create and share care plans for complex high needs patients amongst a patient's healthcare team.

The shares rallied to $4.20 earlier in April, a nine-month high, after the company announced a series of new deals.

"The stock's been exceptionally strong through March and April. It's seen a 60-plus percent return over the past six or eight weeks," Lister said.

Meridian Energy gained 2 per cent to $2.58, having fallen for four consecutive sessions.

Sky Network Television advanced 1.8 per cent to $5.16, and has gained 10.5 per cent this year.

"Sky has had a pretty good run, from being out of favour through December, January, February as people worried about Netflix and the threat of technological change in the sector - that seems to have faded a little bit," Lister said.

Z Energy rose 0.3 per cent to $7.25. The Commerce Commission's decision on whether to approve Z's application to buy Chevron New Zealand's service station chain is due on Friday, having been delayed multiple times.

"People are obviously expecting a green light on that front," Lister said.

Outside the main index, Veritas Investments rose 38.7 per cent to 43 cents, a three-month high. The food and beverage company affirmed its annual earnings guidance and said its three divisions are all showing signs of improvement.

Stripping out one-off and significant costs, profit from continuing operations is expected to be between $3 million and $3.5 million in the 12 months ending June 30. Abano Healthcare gained 5.8 per cent to $8.15.

The medical and dental centre investor has received an unsolicited approach to buy a 50 per cent stake in audiology company Bay International for almost three times book value.