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RedPowerLady's avatar

What makes a baby have a birth weight of 7lbs vs 10lbs?

Asked by RedPowerLady (12576points) October 18th, 2009

What causes babies to have high birth weights vs. ‘normal’ or ‘smaller’ birth weights? I am trying to research this online but am finding more information about extremely high or extremely low birth weights vs. a more typical range of between 5–10 lbs. I will be talking to my doctor about this at some point but I like to be able to form educated questions and having more information helps me do this.

At one point a midwife told me that if you eat a lot of sugar and dairy in your last month your baby will be ‘bigger’. Now of course I know people for whom this was very true and others for whom it was not.

Any ideas?

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31 Answers

ccrow's avatar

Well, you probably already know that of babies born to the same woman, later ones tend to be bigger than earlier ones. I assume from your post that you’re considering ‘high’ to mean more than 10 lbs? So if a woman had a first baby close to that weight, later ones would likely be higher than that…

hearkat's avatar

Very often, when babies have double-digit birthweights, the mother had gestational diabetes… but that is not always the case.

RedPowerLady's avatar

@ccrow I consider 10lbs to be high. But no I didn’t know that information thank you for sharing.

@hearkat Thanx for the response :) I’m hoping I won’t have to worry about that. I’m thinking about those who don’t have gestational diabetes. Or perhaps some moms don’t know they have it because they didn’t get proper prenatal care?

hearkat's avatar

@RedPowerLady: There is someone on Fluther with Ob experience, but I forget who it is – hopefully they’ll log in and get your Question soon. Has your physician commented that your baby might be larger than average? Do you have any other risk factors, like being over 35?

RedPowerLady's avatar

@hearkat No actually i’ve been seeing a midwife until my insurance kicks in on 11/1. It’s just one of those cases where all my friends say to me to make sure what I eat etc.. or I might have a big baby. They are causing me to worry. I’m not over 35 but I am in a high-risk pregnancy only because of my previous loss which does not relate to birth weight at all.

MagsRags's avatar

@hearkat I think that’s me.

Statistically, second babies do tend to be bigger than the first and continue getting bigger until #5 when they start getting smaller again. It seems to have something to do with placental perfusion. And boys tend to weigh about ½ pound more than girls.

Uncontrolled gestational diabetes does cause bigger babies, and they tend to be big in the shoulders and abdomen. It’s because the mother is running high blood sugars and the babies are being overfed through the placenta. Some women don’t meet the diagnostic criteria for diabetes but still run higher than average blood sugar and if they don’t pay attention to how they eat will have bigger than average babies.

Women who gain too much will tend to have a bigger baby and women who are obese before they get pregnant are more likely to have big babies even if they gain a normal amount.

And then there’s the genetic factor. Some babies are genetically prone to be bigger.

hearkat's avatar

@MagsRags: I thought so- but I didn’t want to guess incorrectly.

RedPowerLady's avatar

@MagsRags that is some good information, thank you

laureth's avatar

Side question. What’s wrong with bigger babies, besides the obvious “Ouch!” factor? Wouldn’t they have a better start in life than a smaller baby?

RedPowerLady's avatar

@laureth double digit babies are often take out via c-section and I am a proponent of vaginal birth when possible

laureth's avatar

GAH! Okay, I see your point! Thanks. :)

MagsRags's avatar

@laureth there are other issues as well. Babies with big shoulders are at risk for shoulder dystocia, where the shoulders get stuck with the head delivered. It’s a life threatening emergancy for the baby – the midwife or doctor has only a few minutes to get the shoulders unstuck to avoid brain damage or death, and in the process, sometimes the baby can get injured with a broken arm or collarbone..

MagsRags's avatar

The babies who are big from mom’s blood sugar being too high during pregnancy also have problems with hypoglycemia the first 24–48 hours after birth. Their pancreas is chugging along on hyperspeed to keep up with the flood of sugar through the umbilical cord – they’re born, the cord is cut, and their supply is cut off, but the pancreas keeps on pumping for awhile. The baby’s blood sugar can get low enough to cause severe distress, so they have to be monitored closely, checking their blood sugar frequently and intervening with IV blood sugar if necessary for the first few days.

RedPowerLady's avatar

@MagsRags So how does one know if their blood sugar is high, is that done through a blood test, a urine test, or are there symptoms?

MagsRags's avatar

It used to be that women were screened if they had risk factors for gestational diabetes – age over 35, history of big babies, stong family history of diabetes, personal obesity. You pick up most diabetics that way, but will miss some. These days, most practices screen all pregnant women between 26 and 28 weeks. We have them dring 50 grams of glucose (the equivalent of 1½ cups of sweetened grape juice and measure blood sugar an hour later. If the level is 140 or higher, we send the woman on for a 3 hour glucose tolerance test to find out for sure.

casheroo's avatar

hello people! we went over this in this thread http://www.fluther.com/disc/55632/does-birth-weight-increase-with-each-successive-child/ stop trying to terrify me about giving birth again lol

@RedPowerLady I don’t know…but I ate a TON of sugar during my pregnancy with my son. Ice cream, candy, and chocolate daily…I didn’t not have gestational diabetes…I did gain 50lbs, which was more than I should have. My son was a healthy 7lbs 15oz. (21in)
To me, that just showed that what I ate didn’t affect the baby’s weight at all, but it affected MY weight. Because after the labor/delivery, I did lose the normal 13lbs instantly (baby plus placenta plus water weight) and it took more work to get rid of the rest of the weight (after the initial 25lbs)
And like @MagsRags said, you’ll get your GD test soon. Mine will be done at 27 weeks. Bring a book. It’s a born test. You drink this nasty stuff, and they take your blood afterwards.

So, don’t not eat because you’re afraid of having a big child. Genetics are genetics, I’d go by the weight of you and your husband, and even your parents at birth. I also had a midwife feel my son when he was full term (39 weeks) and she estimated his weight at 7lbs 10oz, she was super close! I trust a midwife with that more than an ultrasound…they can be off by A LOT.

MagsRags's avatar

@casheroo I trust the pregnant woman’s estimate even more if she’s had a baby before! There was actually a study that looked at accuracy of EFW estimated fetal weight comparing ultrasound, care providers like OBs and midwives, and the mother. The mothers won. By full term, the margin of error for EFW by ultrasound is +/- 10 to 15%. That’s more than a pound in either direction.

RedPowerLady's avatar

@MagsRags Thank you for telling me that. I’m going to make sure my OB gives me that test just to be safe.

@casheroo Thanx for the personal experience. I enjoy those stories.

MagsRags's avatar

@casheroo please don’t let us rattle you! Most healthy women grow babies that are the right size for them. Your body already knows what do do this time, and if this baby is a bit bigger, it should be fine. ((casheroo))

casheroo's avatar

@MagsRags That’s interesting to know! I definitely didn’t even know what to estimate with my first, but I know this time around once I’m bigger, that I’ll have a better feel for it. Also, the ultrasounds are showing this baby is smaller than my son was (just by the measurements of length and what not) so I’m thinking this baby got more of my husbands genes lol. I’m taller than my husband So, I think this baby will be close to the same birth weight as my first son, which IMO was perfect.

janbb's avatar

My son and daugther-in-law were each in the 7 pound something range. She was on a very healthy diet in France and had a very healthy pregnancy with no problems. Grandson Jake was 8 lbs. 13 oz. at birth(!); she had an easy delivery and he is a very healthy baby. Pay attention to diet, take the tests, but don’t fret.

hearkat's avatar

@casheroo: Regarding your weight gain and baby size, i want to clarify that relatively speaking, you were pretty young when you had Cash, weren’t you?

I was 24 when I had my son, and I was at least 40 lbs. overweight. I was a little worried about gaining a lot, but I believe that our bodies know what they need, so I trusted my hunger and cravings and ate whatever I wanted. I fortunately did not have much nausea, and the day before I delivered I had gained 26 pounds. My son weighed 8 lb. 9 oz, and my old-school Ob/gyn (he delivered most of the kids I grew up with) had predicted over 8 pounds a couple weeks prior to delivery.

casheroo's avatar

@hearkat Yes, I was 20 when I had my son. My OB were the people who were up my butt about my weight gain. I didn’t gain any weight until 17 weeks, and then I just kept gaining (upwards of 7lbs in a week sometimes) My OB said I should gain no more than 30lbs, having been underweight prior to getting pregnant. I felt at that point, being like a pound or two from 30lbs and no where near done the pregnancy, that the weight gain was just going to happen. I never worried about it, although I don’t want to gain as much this time because I do think it had a play into my very long hard labor, and recovery. I’ve been eating healthier this time, but not denying myself…I think there’s definitely a happy medium.

hearkat's avatar

@casheroo: I was relating more to the fact that Cash was an average weight despite your own weight gain. I wonder how much maternal age effects those stats :-/
Thanks for sharing that, and I am glad that things are going well for both you and @RedPowerLady!

Darwin's avatar

My mother was a smoker, and her babies became smaller. I was 9 lbs something, my brother 8 lbs something, and my sister barely 7 lbs, even though she was born “late.” The doctor told her it had to do with not enough oxygen getting to the babies as she continued to smoke.

And yes, gestational diabetes ends up allowing the baby to be “overfed” in the womb and thus end up larger.

Simone_De_Beauvoir's avatar

this might be a tangent, but bigger babies are nothing to fear delivering…our bodies are quite powerful…the idea that some babies are too big is a very modern concept supported by the medical community who doesn’t want to bother

RedPowerLady's avatar

@Darwin that is a good point to consider, my mother had smaller babies as well and was also a smoker.

@hearkat Thank you for the good thoughts.

@Simone_De_Beauvoir Actually the fear is more about the doctors thinking a c-section is necessary as they often do with bigger babies (often unjustly). I believe in the power of a woman’s body and that vaginal birth should be given more consideration. It is scary that 1 in 3 deliveries end up as a c-section.

casheroo's avatar

@RedPowerLady Try not to stress too much. Just prepare yourself as if you’re going to have a vaginal birth, but a c-section can be a life-saving alternative. I’m terrified of having any surgery, especially a c-section but I know it is there in case we need it. I believe we’ve talked about this before, about staying firm and having an outline of your birth plan with you. But, if a doctor told me I need a c-section because of the baby’s size, I’d laugh in their face. My friend just had her third baby, and she usually makes big babies (over 8lbs…that’s big to me) they kept telling her this new baby would be over 10lbs and convinced her to get a c-section…of course the baby was a normal 8lbs and I believe 13oz. They said they made her incision in a good spot for a VBAC, but she could have easily tried to give birth IMO. Doctors (mainly OBs can be such bullies sometimes)

RedPowerLady's avatar

@casheroo Doctors (mainly OBs can be such bullies sometimes) Ya that is what I’m worried about, lol :) I think most of my anxiety is due to our loss and me having a hard time believing everything can go right. But you give some good advice especially about having a firm birth plan. I will make sure to do that!

janbb's avatar

Just to speak up on the other side, you shouldn’t rule out an emergency c-section if that’s what’s called for at the time. With my first son, I went through natural childbirth and did not take any medication for pain. After 19 hours of labor and 3 hours of pushing, I had an emergency s-section because his head wasn’t crowning, and delivered a 7 lbs. 10 oz. beautiful baby. Did I do something wrong? I don’t think so.

I always advise people that you can have a firm birth plan but you don’t know what’s going to happen and how you will actually feel. It’s not a contest; the object is to get a healthy baby out. Certainly, I didn’t want to surgery and I would never schedule a c-section for convenience sake. I was in pain after, but my baby nursed just fine and now is finishing up a Phd (there were some intervening years!) I thhink the most important thing is probably to have a doctor or midwife you trust and certainly to make your wishes known, but be open to change if the situation changes.

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