Basically, the poem discusses the old tradition of marrying girls off young. A 'maid' is usually considered a 'teenager,' in modern terms. As soon as the maid in the poem was no longer a child, she was married off. In those times, that meant she became her husband's property--some people think that indicates that women where very oppressed. That's the reason for the line 'buried before she was born.' In other words, the maid had just finished her child years and had the rest of her life before her, but she was instantly 'chained-down' by her marriage, never having had the chance to blossom.