Obgyno Wino Podcast Episode 68 - Shoulder Dystocia
Updated: Apr 3
"The price one pays for pursuing any profession or calling is an intimate knowledge of its ugly side." - James Baldwin
PB#178 - Published May 2017 (Reaffirmed 2016)
Neonatal complication risk is overall low (5%), including brachial plexus injuries, clavicle fracture, humerus fracture. HIE/death are also possible, but extremely unlikely.
The faster that a shoulder dystocia is resolved, the less likely HIE/death.
It's nearly impossible to predict shoulder dystocia, but risk seems to be higher with larger fetuses and diabetic mothers.
Insufficient evidence to conclude that early induction of labor when fetal macrosomia is suspected decreases the risk of shoulder dystocia.
Steps to resolving shoulder dystocia per ACOG: stop pushing, McRobert's maneuver w/ head traction, suprapubic pressure, rotational maneuvers, then posterior arm delivery. My advice? Get her on all fours way before any of the other maneuvers (Gaskin maneuver).
What is it?
- baby's anterior shoulder gets caught on the maternal pubic symphysis
- posterior shoulder can also get caught up on the sacral promontory
- especially common with fetal macrosomia (wide shoulders relative to biparietal diameter) and precipitous labor (adequate rotation of the shoulders doesn't occur during passage through the birth canal)
- incidence is 0.2-3%
- look for the "turtle sign", in which the fetal head retracts into the vagina slightly instead of continuing outward during expulsion at the end of 2nd stage of labor (may be suggestive of an impending shoulder dystocia)
- increased risk for postpartum hemorrhage (10%) - *unrelated to maneuvers to relieve dystocia
- increased risk for 4th degree laceration (4%) - *unrelated to maneuvers to relieve dystocia
- symphysial separation and femoral cutaneous neuropathy may result from extreme hyperflexion of the hips (<1%)
- if any fetal manipulation is required, there's an increased risk for obstetric anal sphincter injuries (OASIS) (unknown incidence as diagnosis is difficult)
- if you're a maniac and you attempt the Zavanelli manuever (replacing the fetus baby into the uterus and rushing to c-section) or symphysiotomy carry high incidence of cervico-vaginal lacs, uterine rupture, bladder laceration, and urethral injury
- overall low absolute risk (5%)
- increased risk for brachial plexus injuries (Erb's palsy and Klumpke's plasy) and clavicle/humerus fractures
- unclear if brachial plexus injuries have long-term effects
- some evidence that injuries involving fewer nerve roots recover faster (e.g. injury to C5-C6 versus C5-T1); though >50% of brachial plexus injuries occur in uncomplicated vaginal deliveries
- also some reports of radial fracture
- increased risk for hypoxic-ischemic encephalopathy (HIE), especially if >5 maneuvers were required (1% in diabetic mothers, <1% in non-diabetic mothers)
Note: There's always a lot of conversation about time from identification of the dystocia to delivery. Jury is still out because data is mixed. Higher risk of HIE if interval is >10 minutes. Of cases in which the newborn died, in ~50% the interval was <5 min. Only 20% had an interval >10 minutes. Also, fetal compromise was suspected prior to delivery in 25% of cases. Who knows...faster is probably better, though.
We stink at predicting shoulder dystocia
- higher risk among diabetic patients and larger fetuses
- however, by the numbers, most cases are still seen in non-diabetic women with normal-sized fetuses
- history of prior dystocia is a risk factor (estimates vary, but likely >10%), but not a contraindication to vaginal birth by a long shot
- poor predictors? excessive maternal weight gain, obesity, operative vaginal delivery, oxytocin use, multiparity, epidural use, differences in ultrasound discrepancy between biparietal diameter and abdominal circumference, precipitous and prolonged 2nd stage of labor
Inducing labor for suspected fetal macrosomia
- first of all, ACOG doesn't recommend induction of labor at <39 wks unless medically indicated
- a large European study recruited >800 women at 37-38 wga with fetuses measuring >95%tile and randomized the women to expectant management or IOL within 3 days of diagnosis: shoulder dystocia was 1% in the IOL group versus 4% in the expectant management group, no difference in brachial plexus injury or c-section rates
- a meta-analysis including this trial and some others (n= 1190) came to the same conclusions
- another study looked at IOL for diabetic patients at 38-39 wga with suspected macrosomia, and the shoulder dystocia risks were lower in patients who underwent IOL at 38-39 wga (1.4%) versus those expectantly managed beyond 40 wga (10%) (no differences in c-section rate or macrosomia)
- universally ultrasound women in the 3rd trimester is also very challenging, given that fetal growth ultrasound is historically inaccurate late in pregnancy (+/- a pound in the 3rd trimester!), and even more inaccurate if complicated by maternal obesity
- ACOG's official stance: insufficient evidence to conclude that early induction of labor when fetal macrosomia is suspected decreases the risk of shoulder dystocia
C-section for prevention of shoulder dystocia
- number needed to treat (NNT) = 3,695 cesarean deliveries to prevent a single permanent brachial plexus injury if fetus >4500 gm
- NNT = 443 if mom is diabetic
- conclusion: reasonable to offer elective c-section if fetal weight is estimate to be >5000 gm in a non-diabetic mom or >4500 g in non-diabetic mom
Preparations prior to the birth if you have a hunch
- reminder everyone to be calm, but tell your helpers that you anticipate dystocia might be coming (you'll have a hunch if you've seen enough dystocias)
- have a stool in the room for a nurse or other birth attendant to be better suited to assist with maneuvers, especially if you work in a hospital with the tall hospital beds
- anticipate need for uterotonics given the increased risk for hemorrhage
- notify peds/NICU staff if available in your facility
How to resolve shoulder dystocia
**If you have the opportunity to practice these maneuvers in simulation on a mannequin, you'll do your patients a huge service.
Step 1: assuming you've already tried some additional traction on the head, ask the patient to stop pushing (1 sec)
Step 2: assess quickly to determine if the anterior or posterior shoulder is stuck and direct the traction in the opposite direction (5 sec)
Step 3: extreme McRobert's (hips flexed) (10-20 sec)
Step 4: fundal pressure applied from the side opposite to the direction of the fetal gaze (feel for the baby's eye sockets to know for sure); the idea here is to compress the bisacromial diameter) (10 sec)
Step 5: relax and breathe. If that shoulder is still stuck, try the Wood's screw or Rubin maneuvers. The former is done by applying suprapubic pressure while applying pressure with your fingers to the anterior aspect of the posterior shoulder. The latter is done by applying pressure to the posterior aspect of the posterior shoulder (reverse Wood's screw). (20-30 sec)
Step 6: relax and breathe. Reach in and pull the posterior arm out. This will reduce the bisacromial diameter drastically, but it can be very hard to do and may result in (or require) humeral or clavicular fracture. (20-30 sec)
Step 7: Start over. The use of these maneuvers will result in safe delivery in under 4 min 95% percent of the time. Episiotomy may be helpful in performing the maneuvers if you are unsuccessful on first pass. Breathe.
Note: After Step 2, I will generally position the patient into Gaskin's maneuver, which is simply having her get into all fours. This is often enough to resolve any dystocia. Thanks midwife mentors!