This is really, really confusing as the literal meaning of "don't have a baby" — being pregnant or give birth to a child — does not fit the context at all.
My guesses are:
Don't act like a baby, be brave and face it.
Do nothing else, so as not to cause any further troubles , since we are already in great mess.
Other meaning that I don't know.
Could anyone help with this epic mystery here? And if possible, but not necessary, show me some similar examples?
The context is:
"I" am Louisa's sister. Louisa is a carer of a quadriplegic, Will，rich and young, who is going to do euthanasia. Now the tabloids get this information from Lou's ex boyfriend Patrick, and they besieged our house, trying to get "my sister's side of story of Will."
Here is the sentence:
‘I’m from The Globe. I wondered if I could have a quick word?’
I could hear the confusion in Lou’s voice.
‘The newspaper?’ I stepped behind my sister. I saw then the notepad in the woman’s hand.
‘Can I come in? I’d just like to have a little chat with you about William Traynor. You do work for William Traynor, don’t you?’
‘No comment,’ I said. And before the woman had a chance to say anything else, I slammed the door in her face.
My sister stood stunned in the hallway. She flinched as the doorbell rang again.
‘Don’t answer it,’ I hissed.
I began to push her up the stairs. God, she was impossibly slow. It was like she was half asleep. ‘Granddad, don’t answer the door!’ I yelled. ‘Who have you told?’ I said, when we reached the landing. ‘Someone must have told them. Who knows?’………
‘Does this mean he’s dead?’ Her eyes had filled with tears.
‘No, it just means some arse is trying to cash in.’ I thought for a minute.
‘Who was that, girls?’ Mum’s voice came up the stairwell.
‘No one, Mum. Just don’t answer the door.’
I peered over the banister. Mum was holding a tea towel in her hands and gazing at the shadowy figure visible through the glass panels of the front door.
‘Don’t answer the door?’
I took my sister’s elbow. ‘Lou . . . you didn’t say anything to Patrick, did you?’
She didn’t need to say anything. Her stricken face said it all.
‘Okay. Don’t have a baby. Just don’t go near the door. Don’t answer the phone. Don’t say a word to them, okay?’
Me Before You by Jojo Moyes