In case you don't know what a baby pool is, or what it looks like, it is a game where everyone in your office guesses the date that they their pregnant co-worker will have her baby. Sometimes it includes the baby's weight and length, too. The person who comes the closest to guessing the correct date, wins!
Recently, my SO's office did a baby pool and he texted me to ask me what a good baby weight to guess might be. (I told him I'd guess between 7 and 8 pounds) He brought home a copy of the calendar with everyone's date (and length and weight) guesses on it so that I could see how much he knew about labor/birth from listening to me - he did not guess on the moms' actual EDD, but guessed a due date after the mom's due date. But what was interesting to me about the calendar is that every single person in the office guessed before the due date except my SO and one other gentleman who had 3 kids. However, the latest guess was only a couple days past the EDD. So I wrote on the calendar the latest guess date - exactly her 41 week mark. And I was right!
So, here are some tips for guessing in a Baby Pool, based on my knowledge of pregnancy and childbirth in the United States if your pregnant co-worker is a First Time Mother:
1. Weight: Go with 7.5 lbs.
I even asked a perinatal epidemiologist about this one - for a first time mother this is the average. This is the hardest to guess, though - babies at term can range anywhere from 5.5 pounds to 10 pounds.
2. Length: Go with 21 inches.
I'd say that the babies I've seen born have been between 19 and 22 inches, with the most common at 21 inches.
3. Due Date: Guess exactly at their 41 week mark (one week after the estimated due date).
A. Most first time mom's have their babies past their due date.
B. Most obstetricians get trigger happy and will find a reason that mom must be induced at 41 weeks. This is certainly true of the doctors in my area. Despite the fact that you're not "post dates" until after 42 weeks, and most first time moms have longer pregnancies, and induction on a first timer doubles the chance of a c-section, and many of the reasons give are not evidence-based (i.e. suspected "big baby"), most OB's will convince most mothers to agree to an induction at 41 weeks.
Another bonus: Sometimes a mom who has her induction scheduled for the next day will spontaneously go into labor the night before.