You can use perfectly to emphasize an adjective or adverb, especially when you think the person you are talking to might doubt what you are saying. 完全地 (尤用在认为对方有疑虑时以示强调)
adverb [程度副词]完美地,极佳地;绝对地,完全地
There's no reason why you can't have a perfectly normal child. 没有理由说明你生不出一个完全正常的孩子。