The nurse's question most likely foreshadows that what the nurse is about to share may have very serious consequences.
The Nurse was the one who had looked after Juliet since her birth. She was a person with whom Juliet would share all her affairs with. She was the one who wanted Juliet to get a man who would provide her with all the worldly happiness. Though she wants Juliet to get a husband of her choice but is afraid of the sacrifices that the love will bring to her. She questioned Romeo of his seriousness of love towards Juliet and then approved them of moving ahead. She was scared of the consequences which the marriage will bring to the family.
