While newborns vary in size and shape as much as adults do, full-term babies tend, on average, to weigh between 5 pounds, 11 ounces and 8 pounds, 6 ounces. They're usually between 19 and 21 inches long, with a head circumference of about 13 1/2 inches.
Your baby is more likely to be on the larger side at birth if:
- You and your partner are larger than average
- Your baby is a boy
- You developed gestational diabetes during pregnancy
- Your baby was overdue
Your baby is more likely to be on the smaller side at birth if:
- You and your partner are smaller than average
- Your baby is a girl
- You suffered from high blood pressure or asthma during pregnancy
- You had poor nutrition habits during pregnancy
- You smoked, drank, or used drugs during pregnancy
- You gave birth to multiples
As you can see, there are many contributors to birth size. Thus, it's not possible to accurately predict childhood or adult size from how big or small your baby was at birth. A tiny newborn won't necessarily be a petite adult, and a large baby isn't guaranteed to grow up to be a football player.