How big is a big baby?
A big baby or a baby with Macrosomnia is defined as a baby with a birth weight that is more than 8lbs 13oz(1). 89.6% of babies are born weighing 8lbs 13oz or less. This means that even though macrosomia is somewhat uncommon, it’s still frequently suspected.ย
How is big baby or macrosomia diagnosed?
Because of the inaccuracies of ultrasound, ๐ญ/๐ฏ ๐๐ผ๐บ๐ฒ๐ป ๐ฎ๐ฟ๐ฒ ๐๐ผ๐น๐ฑ ๐๐ต๐ฎ๐ ๐๐ต๐ฒ๐ถ๐ฟ ๐ฏ๐ฎ๐ฏ๐ ๐๐ถ๐น๐น ๐ฏ๐ฒ ๐ฏ๐ถ๐ด. One of the big reasons for the inaccurate fetal weight prediction is because different sonographers can use different equations to predict birth weight. The equation that has had the most accuracy is when the babyโs abdominal measurement is used.
Technology can NOT accurately predict a big baby.
Factors linked to macrosomia
Your baby being suspected of macrosomia increases risks
Why is it so important to know that fetal ultrasound weight predictions are so inaccurate?
Because there are ๐บ๐ผ๐ฟ๐ฒ ๐ฟ๐ถ๐๐ธ๐ ๐ณ๐ผ๐ฟ ๐ฏ๐ฎ๐ฏ๐ถ๐ฒ๐ who are ๐ฆ๐๐๐ฝ๐ฒ๐ฐ๐๐ฒ๐ฑ ๐ผ๐ณ ๐ฏ๐ฒ๐ถ๐ป๐ด ๐ฎ ๐ฏ๐ถ๐ด ๐ฏ๐ฎ๐ฏ๐ ๐๐ต๐ฎ๐ป ๐ฏ๐ฎ๐ฏ๐ถ๐ฒ๐ ๐๐ต๐ผ ๐ฎ๐ฟ๐ฒ ๐๐๐ง๐จ๐๐๐๐ฌ ๐๐๐! Remember, ๐ญ/๐ฏ ๐๐ผ๐บ๐ฒ๐ป ๐ฎ๐ฟ๐ฒ ๐๐ผ๐น๐ฑ ๐๐ต๐ฎ๐ ๐๐ต๐ฒ๐ถ๐ฟ ๐ฏ๐ฎ๐ฏ๐ ๐๐ถ๐น๐น ๐ฏ๐ฒ ๐ฏ๐ถ๐ด. When babies are suspected to be big, they have higher rates of โstalledโ labor, higher induction rates, and ๐ฎ-๐ฏ๐ ๐ต๐ถ๐ด๐ต๐ฒ๐ฟ ๐ฐ๐ฒ๐๐ฎ๐ฟ๐ฒ๐ฎ๐ป ๐๐ฒ๐ฐ๐๐ถ๐ผ๐ป ๐ฟ๐ฎ๐๐ฒ compared to babies who are born big without the prior diagnoses or suspicion!
๐จ๐น๐๐ฟ๐ฎ๐๐ผ๐๐ป๐ฑ๐ ๐ต๐ฎ๐๐ฒ ๐ฏ๐ฒ๐ฒ๐ป ๐ณ๐ผ๐๐ป๐ฑ ๐๐ผ ๐ข๐ฉ๐๐ฅ ๐ฒ๐๐๐ถ๐บ๐ฎ๐๐ฒ ๐ฎ ๐ฏ๐ฎ๐ฏ๐โ๐ ๐๐ถ๐ด๐ต๐ ๐ณ๐ฌ% ๐ผ๐ณ ๐๐ต๐ฒ ๐๐ถ๐บ๐ฒ
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Yet, Nondiabetic women only have aย 7.6%ย chance of having a big baby(5)! How crazy is it that SO many birthing people are told that their baby is going to be large when such a small amount actually have large babies? Studies have found that only 1.3% of babies are born weighing more than 9lbs 15oz.
Is having a big baby dangerous?
Most of the concern around big babies is that people have become cultured to believe birthing a big baby is more dangerous for the birthing person and baby. Letโs talk about each potential risk.
Still Birth
Some care providers will stress that big babies have a higher chance of being born stillborn. The evidence does not show this. It is actually the babies on the small extreme that are more likely to be stillborn(4).
Shoulder Dystocia
Shoulder dystocia is the prolonged delivery of a babyโs head to the delivery of their shoulders. While diabetic mothers are more likely to have shoulder dystocia, there is no possible way to predict shoulder dystocia. Statistically, only 0.65% of babies who are born weighing treated than 8lbs 13oz experience shoulder dystocia. The risk of these babies receiving nerve damage from shoulder dystocia is 0.009%. Learn more about shoulder dystocia by reading my blog about Shoulder Dystocia Here.
Birth Fractures
It is rare for a baby, even a big baby, to experience birth fractures. Only 0.54% of big babies have fractures during birth compared to 0.08% that smaller babies do(6).
Interventions for Suspected Big Babies
The suspicion of a woman having a big baby doubles her chances of having a cesarean section even though there is no evidence of improved outcomes for mom and baby. It is important to remember that C-sections come with their own risks as well.
When babies are suspected to be big, they have higher rates of โstalledโ labor, higher induction rates, and ๐ฎ-๐ฏ๐ ๐ต๐ถ๐ด๐ต๐ฒ๐ฟ ๐ฐ๐ฒ๐๐ฎ๐ฟ๐ฒ๐ฎ๐ป ๐๐ฒ๐ฐ๐๐ถ๐ผ๐ป ๐ฟ๐ฎ๐๐ฒ compared to babies who are born big without the prior diagnoses or suspicion!
Multiparous women with a previous delivery of a macrosomic infant were at lower risk of maternal complications (3)
Care Providers may use Macrosomnia as a reason for Induction. As of 2018, the American College Of Obstetricians & Gynecologists (ACOG) doesย NOTย recommend induction in cases of macrosomia (2). Although induction is not recommended, care providers of 2/3 of the women who were told they were going to have a big baby discussed induction and/or cesarean section. Can you see how many women are undergoing induction or planned cesarean for macrosomia when ACOG doesnโt recommend it and when big babies cannot be diagnosed by technology?ย Less than half of women whose Care providers counseled them about big babies gave birth vaginally. Letโs remember again that birthing people only have a ๐ต.๐ณ% chance of having a big baby!
Weighing the Risks of having a big baby
As an expecting parent, you can look into the potential risks and weigh your options. Does your baby potentially being big really pose a threat? Do we have any of the risk factors that are linked to big babies? Are the risks of having a big baby higher than the risks of a planned induction or cesarean? To aid you in your decision-making process, I have included several resources below!
If you are needing additional guidance and support, please donโt hesitate to book a free consult with me about providing doula services byย Clicking Here. Want to continue to learn more about your options in pregnancy and birth? Check out my other blog postsย Here.
Resources about Big babies
Macrosomia Definition
Practice Bulletin No. 173: Fetal Macrosomia
What are the birth implications for a suspected big baby? Evidence-Based Bith Podcast
Maternal and neonatal complications of fetal macrosomia: systematic review and meta-analysis
Birth weight percentile and the risk of term perinatal death
Risk factors for recurrent macrosomia and child outcomes
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Jenni Jenkins โ Sekine is an Oklahoma Bereavement, Birth, & Postpartum Doula and Child Birth Educator who serves her Central Oklahoma community. She is also a midwifery assistant with Holistic Birthing Services and began her journey as a student midwife with the Midwives College of Utah in 2022.
Jenni is also the creator & facilitator of the Kaleidoscope OKC LGBTQ Family Support Group & the Nurture Oklahoma Live Interview Series.
To learn more about Jenni, please click here.
