阅读理解 2016考博英语 passage one

Helping the child develop good sleep habits in childhood takes time and parental attention, but it will have beneficial results throughout life. 请教，解析上说，让步状语从句helping……attention,中分词短语"Helping the child develop good sleep habits"做从句的主语，可这不应该是一个完整的句子吗，怎么算是分词短语？如果Helping the child develop good sleep habits是句子那和谓语动词"takes"之间是不是应该有连词？