# What will your baby's weight at birth be?

1298 Views 16 Replies 10 Participants Last post by  CalebsMama05
I found the neatest formula on the web and have put it into an Excel spreadsheet. It looks at a number of factors, including weight gain in the third trimester. I will happily enter your data and post the results, just post the following information: (You need to be past 26 weeks for this to work!)

1. Getational age (how old is your baby in days) or the date of your LMP :
2. Sex of the baby (if you know):
3. Your height (feet and inches):
4. Your weight at 26 weeks:
5. Third trimester weight gain
a. number of pounds gained :
b. number of days that occured in :
(So from week 27 on, how much have you gained in how many weeks - so if you are 28 weeks, and gained 5 lbs, that would be 5 lbs in 7 days)

6. Number of previous births:
__________________________________________________ ______________

I'm not there yet but I have been playing with the formula, if I keep gaining at my current pace my data would look like this on May 15th:
1. Gestational age: 225 days
2. Height: 5 foot 4 inches
3. Sex of baby: girl
4. Weight at 26 weeks: 163
5. 4 lbs in 28 days
6 previous births: 0

And the formula spits out that with that data my baby would be 6.065 lbs at birth!

I know it is a little early to do this, but since you need to know your weight from 26 weeks on for it to work, I thought I should post this now!
See less See more
1 - 17 of 17 Posts
I'll play!

1. Getational age (how old is your baby in days) or the date of your LMP :
October 1st LMP
2. Sex of the baby (if you know):
male
3. Your height (feet and inches):
5'6"
4. Your weight at 26 weeks:
154
5. Third trimester weight gain
a. number of pounds gained : 0
b. number of days that occured in : 0
(So from week 27 on, how much have you gained in how many weeks - so if you are 28 weeks, and gained 5 lbs, that would be 5 lbs in 7 days)

6. Number of previous births: 0

I guess it would probably be best to do this later when I can calculate how much I've gained in the 3rd trimester. If it makes a difference all 13 lbs that I've gained was in the 2nd trimester.
See less See more
Well assuming you don't gain a pound in the third trimester -
The magic formula says 5.42 lbs! I'll happily run it again for you in a month or two once you know how much more baby you gain!
See less See more
1. Getational age (how old is your baby in days) or the date of your LMP : 09/27/05
2. Sex of the baby (if you know): male
3. Your height (feet and inches): 67.5
4. Your weight at 26 weeks: 165
5. Third trimester weight gain
a. number of pounds gained : predict 15-20 lbs
b. number of days that occured in : 90ish?

Or you could plug in 10 lbs in 45 days?

6. Number of previous births: 3
See less See more
Ooh what fun!!!

1. the date of your LMP :9/29/05
2. Sex of the baby :Male
3. Your height (feet and inches):66
4. Your weight at 26 weeks:202
5. Third trimester weight gain
a. number of pounds gained :1.5
b. number of days that occured in :7

6. Number of previous births:0
See less See more
Ooh, count me in!!!

1. Getational age (how old is your baby in days) or the date of your LMP : I'm guessing since i haven't had one snce i got pg with Emma..so, I am 195 days pregnant.
2. Sex of the baby (if you know):girl
3. Your height (feet and inches):5'6"
4. Your weight at 26 weeks: 198
5. Third trimester weight gain
a. number of pounds gained : 2
b. number of days that occured in :7
(So from week 27 on, how much have you gained in how many weeks - so if you are 28 weeks, and gained 5 lbs, that would be 5 lbs in 7 days)

6. Number of previous births:2
__________________________________________________ ______________
See less See more
Okay - realized I need to adjust the gestational age a bit when we are "predicting" into the third trimester! So here goes:

***************************
PancakeGoddess / Amy:

Going forward 45 days with your weight gain estimate of 10 lbs it comes up with 7.909 lbs.
************************
Maxine45:

As of today (with only one week of weight gain data) is says 6.100 lbs.

**************************
ksjhwkr:

As of today (with only one week of weight gain data) is says 6.212 lbs.

Ladies the more I play with this formula, it seems to put a great deal on emphasis on the gestational age in relation to the weight gain - so those numbers should increase as we get further along. If I adjust the gestational age by a month most of the estimates go up about a pound!

So I just ran my own, using my due date as "today's date", so full term, with my full predicted weight gain - and instead of 6.065 lbs, it came back with 8.09!
See less See more
yea, this is a strange formula,but very interesting. I think previous babies' weights should be a factor. If I have a baby that small I'll be thrilled.
Quote:
 Originally Posted by Heather_in_LasVega Okay - realized I need to adjust the gestational age a bit when we are "predicting" into the third trimester! So here goes: ksjhwkr: As of today (with only one week of weight gain data) is says 6.212 lbs. Ladies the more I play with this formula, it seems to put a great deal on emphasis on the gestational age in relation to the weight gain - so those numbers should increase as we get further along. If I adjust the gestational age by a month most of the estimates go up about a pound!
Well, with Emma I gained 76 lbs (that's right, 76!!!) and she was 7.8, with Seth, I gained 42 and he was 9.3!!! So, I doubt that this kiddo will only be 6.2. It will be fun to see what it is as I get further along. This is fun though!!!
See less See more
I found the formula and LOL it said 13.5 lbs. Um. I'll check again after I've reached the third trimester and I'm not simply guessing at numbers. Pretty cool though!
Is it possible to test with previous babies to see how accurate it is? I would need to find out my third trimester info but that sounds like a good way to test it out...
I can probably find all of my info to volunteer from last time to test it out, if you'd want to.
See less See more
ooh here's my info from caleb you can tell me what it said...

1. Gestational age: lmp June 3, 2004
2. Height: 5 foot 7 inches
3. Sex of baby: boy
4. Weight at 26 weeks: 158
5. 25lbs in 13wks
6 previous births: 0

his actual birth weight was 9lbs 10oz. i'm interested to know if it was right!
The way things are going, dd1 was 7,5 dd2 was 8,5. So i imagine that this dc will be about 9,5lbs.
:
See less See more
CalebsMama05 - Well the formula kicked out 8.077 lbs.

So not an exact science here - but still interesting!
If anyone wants to run it on your own I thought I would post the formula, you will quickly see why I put it into Excel!

Birth weight (g) = gestational age (days) x (9.38 + 0.264 x fetal sex + 0.000233 x maternal height [cm] x maternal weight at 26.0 weeks [kg] + 4.62 x 3rd-trimester maternal weight gain rate [kg/d]] x [number of previous births + 1]).

Perform all multiplications before the additions.
Gestational age is the stage of your pregnancy in days, or days since the onset of your last normal menstrual period plus 14.
For fetal sex, use 1 for a boy, -1 for a girl, or 0 if sex is unknown.
For mother's height, inches multiplied by 2.54 gives you centimeters.
For the mother's weight, pounds divided by 2.2 gives you kilograms.
For the baby's birth weight, take the number from your calculation and divide by 453 to get your baby's estimated weight in pounds.
See less See more
wow. I wish i had excel lol.

i might actually have gained 30lbs my last trimester. all i really remember from my pregnancy was that i gained a LOT of weight (79lbs altogether)
1 - 17 of 17 Posts