Kate, who is expecting her third child, is suffering from severe pregnancy sickness and has missed two public events this week

By Simon Perry
September 06, 2017 02:27 PM

Like any proud parent, Princess Kate is looking forward to seeing her son Prince George off on his first day of school on Thursday.

But Kate – who revealed on September 4 she is expecting her third child — is suffering from severe morning sickness, Hyperemesis Gravidarum (HG), making her appearance at the school gates increasingly doubtful.

A source tells PEOPLE that there is a “fair chance that she will not be able to attend tomorrow.”

As planned, George will have dad Prince William to hold his hand as he walks into the private Thomas’s Battersea school, about four miles from the family’s home at Kensington Palace.

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Kate, 35, wasn’t able to go to the two engagements she had planned on Monday — the cancellation of which forced the palace to make the pregnancy announcement — and Tuesday, when she was slated to accompany William and Prince Harry as they met victims and those who helped out at the Grenfell Tower tragedy.

A royal source told PEOPLE earlier in the week, “Like any mother she would be keen to be there for the Prince George’s first day of school, but we will have to wait and see how she is and a decision will be made nearer the time.”