Bumbo seat should be avoided as it has the risk of topple when baby is sitting in it. http://www.dailymail.co.uk/news/article-2188714/Four-million-Bumbo-Baby-Seats-recalled-dozen-reports-skull-fractures-infants.html
If you decided to let baby sit in Bumbo please monitor closely and do not leave the baby alone.
Expertise advises not to sit up the baby. We should let baby develop their motor skills at their own pace. You may read up more on this article to understand more and how to provide a right environment for baby to learn to sit. http://activebabiessmartkids.com.au/articles/please-sit/
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