United Kingdom, Feb. 1 -- Charlie McDowell has hit back at social media users who posted "unkind messages about surrogacy".

The 41-year-old screenwriter and Lily Collins, his wife, recently announced that they've welcomed a baby girl via a surrogate, and Charlie has now taken to Instagram to defend their decision.

He wrote on the photo-sharing platform: "Thank you for all the kind messages and love. We are overjoyed and very grateful. In regards to the unkind messages about surrogacy and our path to having a baby - it's OK to not be an expert on surrogacy.

"It's OK to not know why someone might need a surrogate to have a child. It's OK to not know the motivations of a surrogate regardless of what you assume. And it's OK to spend less t...