Children don't complete their set of 20 baby teeth until they are two to three years old.

孩子到两三岁时才长齐20颗乳牙。

《柯林斯英汉双解大词典》

WHO recommends exclusive breastfeeding until a baby is six months old, and continued breastfeeding with the addition of nutritious complementary foods for up to two years or beyond.

WHO建议给婴儿用母乳喂养到6个月大，然后继续用母乳和添加了营养的补充食物喂养至2岁或更大些。

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The maternal uncle, Feng, and the young boy led the party, followed by the mother, riding with the elder maid, Bluehaze, who was holding a baby of two years old.

冯舅爷和一个年轻小伙子领头儿，随后车上是太太跟大丫鬟青霞，青霞怀里抱着一个两岁大的小孩儿。

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The Family Nurse partnership scheme sees nurses or midwives regularly visit first-time mothers under the age of 20 until their baby is two years old.

BBC: More help for disadvantaged mothers