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Paul Sancya, Associated Press
Michael and Lauren Whiteley, from left, check on their identical triplets Alexander, Timothy and Nicholas at their home in St. Clair Shores, Mich., Wednesday, Feb. 25, 2015. The brothers were born at 34 weeks via C-section on Jan. 25. About 4,300 triplet births are recorded each year in the U.S., according to the Centers for Disease Control and Prevention. But these births are rarer because the triplets were conceived naturally, without fertility drugs.

ST. CLAIR SHORES, Mich. — A suburban Detroit couple who have two older children are adjusting to life after becoming parents to identical triplets — a multiple birth a doctor calls rare.

The Whiteley family of St. Clair Shores is celebrating the one-month birthdays Wednesday for Alexander, Nicholas and Timothy.

Lauren Whiteley says it "was the shock of a lifetime" when an ultrasound revealed three fetuses. She wasn't taking fertility treatments, which wouldn't play a role: identical siblings are only born through natural conception.

She and her husband, Michael, say triplets don't run in their families. Their older sons are 3 and 2.

Dr. Savitri Kumar at Henry Ford Hospital in Detroit, where the triplets were born, says data on triplet births by natural conception is "very variable" but one-in-a-million is "the most commonly quoted."