DUBLIN (Reuters) - The number of births outside marriage in the Irish republic hit 4,275 in January-March this year, its highest level since detailed records began in 1976. Of 13,388 births registered in the first three months of this year, 32 percent were to unmarried parents. The number has risen steeply since 1976, when there were 640 births outside marriage in the first quarter out of 17,000 live births, the data showed. It has more than doubled in the past decade, from 1,670 in January-March 1989. The total number of births in the republic has fallen from around 70,000 in 1976, representing a rate of 21 births per 1,000 people, to around 52,000 or 14 per 1,000 last year.