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Human reproduction 人类繁衍 Life begins at 45 45岁也能生娃 Hope for older mothers 高龄母亲的福音 WHEN it comes to reproduction, men have it easy. 讲到繁衍，男人表示压力很小。 Almost to the end of their lives most have an ample supply of sperm. 大多数人直到去世前都拥有充足的精子。 Women are not so lucky. 女人可就没这么幸运了。 They are born with a supply of eggs that typically runs out when they reach middle age. 人到中年，她们就会耗尽出生时携带的卵子。 That could be about to change, however. 不过，这一情形很快就能得到改变。 Researchers have confirmed that women harbour ovarian stem cells, and that these cangive rise to new eggs. 研究者们证实，女人拥有卵巢干细胞，而这种细胞能成为新的卵细胞的来源。 Stem cells have the ability to divide continuously and to change into different types of cells. 干细胞具有不断分裂的潜力，可以分化成许多种类的细胞。 Stem cells from adults can produce a variety of cell types, in addition to those that makeup the tissue in which they are found. | 
