* Total sales in 11 weeks to March 28 up 5.6 percent
* UK like-for-like sales up 3.7 percent
* International sales up 40 percent
* Sees margin pressure in 2009/10 due to currency
* Shares down 5.7 percent at 0822 GMT (Adds further details, CEO, analyst comments, shares)
By James Davey
LONDON, April 2 (Reuters) - Mothercare Plc, the British mother and baby products retailer, reported better than expected fourth-quarter sales but cautioned on the outlook for margins in its new financial year, sending its shares lower.
The firm, which trades from over 1,000 stores worldwide, said on Thursday total sales increased 5.6 percent in the 11 weeks to March 28.
Sales at UK stores open at least a year increased 3.7 percent -- a 15th consecutive quarter of like-for-like growth.
This compares with analysts' forecasts of a flat to slightly positive outcome and a 1.1 percent increase in like-for-like sales in the third quarter.
Sales in the 51-country international division increased 40 percent, following a 49.1 percent rise in the previous quarter.
Mothercare said its gross margin was in line with expectations but it cautioned margins would come under pressure in the 2009/10 year due to the weakness of sterling, partly offset by currency gains in the international division.
"Overall we're saying that there will be a decline (in gross margin) beyond and above this year (2008/09) because of the collapse of sterling," Chief Executive Ben Gordon told reporters.
Analysts at Singer Capital Markets estimated the effect on UK gross margins could be in the range of 75 to 100 basis points.
Shares in Mothercare, which have risen 13 percent in the last six months, were down 22.5 pence, or 5.7 percent, at 378.75 pence, at 0822 GMT, valuing the business at 312 million pounds ($447.6 million)s
Group sales for the full year increased 6.9 percent and the group remains debt free
Before Thursday's update, analysts were forecasting an underlying pretax profit of 35.2 million to 38.7 million pounds for the year ended March 28, according to Reuters Estimates, compared with 38.6 million pounds in the previous year.
Many UK retailers are struggling as cash-strapped consumers rein in spending amid rising unemployment, falling house prices and fears of a long and deep recession.
But Mothercare has bucked the trend as parents continue to spend money on their children even if they have stopped spending on themselves.
"We feel that our (UK) market is resilient but by no means immune to a trading downturn," said Gordon.
The firm is also benefiting from its aggressive international expansion, a fast-growing Internet business and the continuing integration of the Early Learning Centre brand it purchased in 2007.
The CEO was upbeat on the outlook for the international division despite the slowdown in growth from quarter three to four and the global economic downturn.
"The Mothercare business is quite immature in most of the markets that it's in, so there's still opportunity to grow stores and like-for-like sales," he said.
The group plans to open at least 100 overseas stores every year for the foreseeable future, focusing on the Middle East, Eastern Europe, China and India.
(Editing by Greg Mahlich; Editing by Rupert Winchester)