For babies, the journey down the birth canal and into your open arms isn't always an easy one. One roadblock that might occur during labor and delivery is shoulder dystocia.

Here's what you should know about this — thankfully uncommon — complication.

What is shoulder dystocia?

Shoulder dystocia

Shoulder dystocia is when one of the baby's shoulders get "stuck" behind the mother's pelvic bone as the baby begins to be born. The head will deliver, but the birth progresses no further. (The word "dystocia" means slow or difficult labor or delivery.)

How common is shoulder dystocia?

Only about 1 percent of babies born vaginally have shoulder dystocia, although this number may be higher for larger babies — those born over 8 pounds, 13 ounces — and for mothers with diabetes.

What are the signs of shoulder dystocia?

Shoulder dystocia is unpredictable, and it can occur even in women and babies who don't have any risk factors.

If your doctor thinks you might experience shoulder dystocia during your delivery, he or she might recommend a C-section, particularly if your baby weighs more than 11 pounds or if you have diabetes and your baby weighs more than 9 pounds, 15 ounces.

Who is most at risk for shoulder dystocia?

It's hard for doctors to predict which women will experience shoulder dystocia during pregnancy.[1] There are some known risk factors, however, including:

  • Having a baby with macrosomia (i.e., a weight of more than 8 pounds, 13 ounces at birth). Most larger babies don't experience shoulder dystocia, however. In fact, most of the cases of shoulder dystocia are in babies with normal birth weights — which is one reason why shoulder dystocia is hard to anticipate.
  • Having diabetes
  • Having had shoulder dystocia before
  • Being overweight
  • Gaining more weight during pregnancy

Some labor and delivery factors also increase the risk of shoulder dystocia, including:[2]

  • A long pushing phase with slow descent of the baby
  • A forceps delivery, in which a pair of curved, tong-like devices are used to help the baby out of the birth canal
  • A vacuum delivery, in which a suction cup is placed on the baby's head to help guide her out of the birth canal 

Despite these increased risks, most cases of shoulder dystocia occur in women who don't have diabetes and babies who have a normal birth weight.

What are potential complications of shoulder dystocia?

Both you and your baby are at risk for complications of shoulder dystocia, almost all of which come as a result of the maneuvers that might need to be taken to dislodge your baby from the birth canal. Luckily, these complications are rare, and both mothers and babies usually make a good recovery.

Some of these complications include:

  • Nerve injury to the baby
  • Breaks and fractures in the collarbone or arms of the baby
  • Lack of oxygen to the baby (rare)
  • Postpartum hemorrhage (PPH) in the mother
  • Significant tearing of your perineum (the area between the vagina and rectum)
  • Uterine rupture, or a tear to the uterus (rare)

How is shoulder dystocia treated?

If you do have shoulder dystocia during labor, your practitioner may try to change your position to open your pelvis wider, which will allow your baby's shoulders to emerge.

For example, your doctor may ask you to hyperflex your knees up to the abdomen (called the McRoberts maneuver), apply pressure to the top of your pelvis or turn you over so that you're on your hands and knees. He or she may also reach into your vagina to try to manually turn your baby.

Less commonly, you might receive an episiotomy (an incision made in the perineum) or a C-section.

Is there anything you can do to prevent shoulder dystocia?

Unfortunately, shoulder dystocia is often unpredictable — and unpreventable.[3] During pregnancy, try to keep your weight gain within the recommended range. This way, your baby may be less likely to have trouble maneuvering her way through the birth canal.

If your doctor thinks that shoulder dystocia may occur during your labor, he or she may recommend that you deliver via C-section.