What’s Worse: Provider’s Suspicion or a Big Baby?

It’s believed by many OB-GYNs and some midwives (especially hospital-trained ones in the U.S.) that shoulder dystocia is more likely to occur with a big baby. Shoulder dystocia is when the baby’s anterior shoulder gets stuck on the pubic symphysis and requires hands-on maneuvers to release the shoulder after gentle downward traction has failed.

The American College of Obstetrics and Gynecology states, “As birth weight increases, the likelihood of labor abnormalities, shoulder dystocia, birth trauma, and permanent injury to the newborn increases.” [1]. But what does the research say? And do we have a reliable way to know if a baby will be big?

What Are Big Babies?

A big baby or “macrosomia,” some consider 8lbs 13oz and others believe to be 9lbs 15oz at birth. Furthermore, an “extremely large” baby is known to be 11lbs+ [2].

1 in 10 babies in the U.S. are born big, although 1 in 3 pregnant women are told by their practitioner that their baby may be too big. This leads to 67% of women being medically induced and the remaining 37% trying to naturally induce labor.

What Creates a Provider’s Suspicion of a Big Baby?

The short answer: flawed assumptions.

These assumptions include:

1. Big babies are at a higher risk of shoulder dystocia
2. Big babies are at a higher risk for other birth problems
3. We can accurately tell if a baby will be big
4. Induction keeps the baby from getting any bigger, which decreases the risk of cesarean
5. Elective cesareans are beneficial and outweigh the risks. Click here to check out, “The Truth About Elective Cesarean Birth Safety“

The Truth About Big Babies:

1. 7-15% of big babies have difficulty with the birth of their shoulders, but most cases are handled by an obstetrician or midwife without harmful consequences.
2. The risk of complications with a big baby increases along a spectrum depending on the baby’s size. A provider’s suspicion of a big baby carries its own set of risks [3].
3. Both physical exams and ultrasounds are equally bad at predicting whether a baby will be big at birth [4].
4. There is conflicting evidence about whether induction for suspected big babies can improve the health of mothers and babies [5].
5. No researchers have ever enrolled women in a study to determine the effects of elective cesarean for suspected big babies. 

Using Ultrasound to Guess Fetal Weight

Evaluation of fetal weight using ultrasound is not very accurate. This study looked at ultrasounds done soon before the mother gave birth and found newborns with lower birth weights were more frequently overestimated, and newborns with higher birth weights were frequently underestimated [6]. This study also resulted in an increased risk for cesarean birth and no difference in perineal tear grades, shoulder dystocia, postnatal depression, and neonatal acidosis.

Therefore, estimating fetal weight soon before birth did not improve maternal and fetal outcomes and is not recommended. Furthermore, if nothing is going wrong on NSTs and BPPs, even if a baby is measuring a bit behind or a bit ahead, more and more maternity professionals aren’t seeing the benefit of using ultrasound to estimate the weight of a baby at all. 

For more information on fetal ultrasounds, check out: “The Truth About Baby Ultrasounds.”

Is the Provider’s Suspicion More Harmful Than Having a Big Baby?

Which is more harmful: Having a big baby at birth with the provider’s suspicion of a big baby beforehand? Or having a big baby at birth without the provider’s suspicion?

Well, this research study looked at just that and found:

• Induction rate: 42% vs 14% [7]
• Cesarean: 57% vs 17% [7]
• Maternal complications included postpartum hemorrhage (PPH), wound infection, wound separation, fever, and need for antibiotics: 17% vs 4% [7]
• Shoulder dystocia: no difference in the rates of shoulder dystocia in either group [7]. And another study found least half of all cases of shoulder dystocia happen in smaller or normal-sized babies [8].

This result was also supported by another study published in 2015 [9]. Therefore, providers who suspect big babies are far more dangerous for birth than having a big baby. 

However, when suspicions arise, likely in the third trimester of a big or even a small baby, it’s good to utilize an NST and BPP to check how the baby is doing, but if those are good, we shouldn’t treat these pregnancies any different than normal, because that’s what the baby is still telling showing us. 

Lastly, in these situations, educating women on how to kick count is greatly beneficial to ensure the baby is still healthy and happy in the womb, even if they seem a bit larger or smaller than usual. 

If you’re interested, click here to check out my labor and birth story of being induced for a suspected small baby. 

You are encouraged, educated, and empowered! Talk soon, mama. 

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Sources:

[1] ACOG: Macrosomia

[2] U.S. Vital Statistics, 2019.

[3] Beta, J., Khan, N., Khalil, A., et al. (2019). Maternal and neonatal complications of fetal macrosomia: a systematic review and meta-analysis. Ultrasound Obstet Gynecol. [Epub ahead of print]. Click here.

[4] Declercq, Sakala et al. 2013

[5] Boulvain M, Irion O, Dowswell T, Thornton JG. Induction of labour at or near term for suspected fetal macrosomia. Cochrane Database Syst Rev. 2016 May 22;2016(5):CD000938. doi: 10.1002/14651858.CD000938.pub2. PMID: 27208913; PMCID: PMC7032677.

[6] Stubert, J., Peschel, A., Bolz, M. et al. Accuracy of immediate antepartum ultrasound estimated fetal weight and its impact on mode of delivery and outcome – a cohort analysis. BMC Pregnancy Childbirth 18, 118 (2018). https://doi.org/10.1186/s12884-018-1772-7

[7] Sadeh-Mestechkin D, Walfisch A, Shachar R, Shoham-Vardi I, Vardi H, Hallak M. Suspected macrosomia? Better not tell. Arch Gynecol Obstet. 2008 Sep;278(3):225-30. doi: 10.1007/s00404-008-0566-y. Epub 2008 Feb 26. PMID: 18299867.

[8] Nath RK, Avila MB, Melcher SE, Nath DK, Eichhorn MG, Somasundaram C. Birth weight and incidence of surgical obstetric brachial plexus injury. Eplasty. 2015 Apr 28;15:e14. PMID: 25987939; PMCID: PMC4415516.

[9] Peleg D, Warsof S, Wolf MF, Perlitz Y, Shachar IB. Counseling for fetal macrosomia: an estimated fetal weight of 4,000 g is excessively low. Am J Perinatol. 2015 Jan;32(1):71-4. doi: 10.1055/s-0034-1376182. Epub 2014 May 16. PMID: 24839149.

DISCLAIMER: This post is not intended to be a substitute for professional medical advice, diagnosis, or treatment. Always seek the advice of your physician or other qualified health provider with any questions you may have regarding you or your baby’s health. Please read my Medical Disclaimer for more info