The royal is scheduled to fly back Down Under on Monday, 27 April to continue training with the Australian Army, before he undergoes an official tour of New Zealand.
It means he might not meet the royal baby until mid May.
Harry's sister-in-law Kate Middleton is widely believed to be overdue. She herself had previously said her second child was due mid to late April.
It was originally believed Harry would get to meet his niece or nephew shortly after the birth, as he flew into the UK to attend the London Marathon over the weekend.
Kate is due to give birth to her second child at the Lindo Wing. The St. Mary's Hospital in Paddington, London is the same place where she and Prince William welcomed son George in July 2013.
It's not known yet whether the baby will be a boy a girl.
This royal baby will be fourth in line to the throne behind grandfather Prince Charles, father Prince William and brother Prince George. The rules of succession were recently changed meaning the baby will remain fourth in line whether it is a girl or boy and whether any future royal children are male or female. Previously, a later male child would jump above an older female child in the line of succession.
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