36 weeks with second but measuring 37 1/2

This is what I was told at my appointment- they said it just means that she will be a bigger baby but that honestly scares me a little bit... what does that even mean? My first was born at 37 weeks and five days weighing 6 pounds, so I'm a little bit scared of giving birth to an eight or 8 1/2 pounder! She also said that I was only dilated to a one in my cervix was still high.... at this point with my son I was already 3 cm dilated and 90% effaced! Does that mean that she will probably stay in longer than he did?