You may have heard that BMI increases the chances of shoulder dystocia. But by how much?
Let’s look at the evidence and address the common misconception that risk is high when you’re old.
Please note that this article is not a substitute for professional medical advice. Address any questions or concerns with your care provider.
Also, BMI is commonly used in studies to categorize people based on their weight in relation to their height. We use BMI in this article to share information about the risks of shoulder dystocia, but we recognize that BMI is problematic and does not give a complete picture of one’s health.
What is shoulder dystocia?
During vaginal delivery, shoulder dystocia it happens when one or both of a baby’s shoulders get stuck behind the pubic bone. It is a rare but urgent medical emergency.
The good news? Most of the time, shoulder dystocia is treated safely and without complications, thanks to quick responses and special techniques in which the healthcare team is trained.
Occasionally, the baby may have minor injuries, such as a temporary weakness in the arm or, very rarely, a broken collarbone. For the person giving birth, there may be some tearing or bleeding. But keep in mind these complications are not typical.
What is associated with a higher risk for shoulder dystocia?
A study from 2023 examined shoulder dystocia in approximately 10 million vaginal births in the US from 2016 to 2019 (Youssefzadeh et al., 2023).
This data came from National Inpatient Hospital Samplewhich randomly collects information from 20% of hospital records at participating centers in the United States.
The study was designed to accurately represent the United States population by including people with different health conditions.
In the study, women aged 15 – 54 had various conditions such as diabetes (either before or during pregnancy), high blood pressure disorders and more. Some had complications during the birth, such as needing help with tools such as a vacuum cleaner or forceps.
Of all births studied, shoulder dystocia occurred in 228,120 cases. That’s 23 per 1,000 births or 2.3%.
The study found that having a big babydiabetes before or during pregnancy and use of a vacuum at birth were the main factors associated with shoulder dystocia.
Other factors that have been somewhat associated with an increased risk of shoulder dystocia:
- Older or younger age
- Black people (from systemic effects of racism)
- Lower income
- Chronic health conditions
- BMI > 30
- Term premature rupture of membranes
- High weight gain during pregnancy
- Birth after 40 weeks of pregnancy
- Inducing or increasing labor
What is the increased risk of shoulder dystocia with a BMI over 30?
When looking at the numbers in the study, people with a BMI of 30 or higher had a 3.4% chance (or 34 in 1000) of experiencing shoulder dystocia.
By comparison, those with a BMI below 30 had a 2.2% chance (or 22 in 1000).
As highlighted in our article on the increased pregnancy risks debate, let’s look at it from another angle.
Instead of dwelling on the 3.4% risk, let’s take a fresh perspective based on the data.
With a BMI over 30, there is a 96.6% chance of not experiencing shoulder dystocia during labor – and those odds sound pretty good!
Being plus size, you may encounter prejudice where people make unfair assumptions about your health and your chances of having a healthy pregnancy.
Such myths sometimes arise from concerns about shoulder dystocia or soft tissue dystocia. For example, hearing that someone’s vagina is too thick to give birth is scientifically incorrect and deeply hurtful.
Instead of letting misconceptions or negative comments weigh you down, keep the lines of communication open with your care provider. They can offer guidance and events tailored just for you.
Remember, as with the shoulder dystocia statistics, the overall increased risks are generally low during a plus size pregnancy.
Focusing on your wellness during pregnancy and linking it to a size friendly care provideryou set the stage for a more relaxed, positive experience with fewer worries.
bibliographical references
Special thanks to Anna Bertone for her assistance in researching this article.
- Davis DD, Roshan A, Canela CD, et al. Shoulder dystocia. [Updated 2022 Sep 4]. In: StatPearls [Internet]. Treasure Island (FL): StatPearls Publishing; 2023 Jan / ncbi.nlm.nih.gov/books/NBK470427/
- Youssefzadeh AC, Tavakoli A, Panchal VR, Mandelbaum RS, Ouzounian JG, Matsuo K. Shoulder dystocia incidence trends and associated risk factors: A national analysis in the United States. Int J Gynecol Obstet. 2023 Aug. 162(2):578-589. doi: 10.1002/ijgo.14699. Epub 2023 Mar 1. PMID: 36707062.
Jen McLellan is a certified childbirth educator, published author and founder of Plus Size Birth and host of the Plus Mommy Podcast. For over a decade, she has advocated for plus-sized people, and the National Institutes of Health supports her work. Jen has been featured in major publications including the New York Times, Glamor and the Huffington Post. She helps people navigate the world of pregnancy, shares tips for embracing your body, and laughs through the adventures of parenthood.
