Your pelvis is a group of bones located in the lower part of your torso, between your lower back and your thighs. It has several important functions, including:

  • supporting the weight of your upper body
  • acting as a connection point for your lower limbs, as well as various muscles
  • helping you stand, walk, or run
  • protecting the organs located in or around the pelvic area

The shape of the pelvis often differs between males and females. A female’s pelvis is generally wider and more open than a male’s pelvis. This helps with vaginal childbirth.

Even among females, though, pelvis shape varies. Generally speaking, there are four main pelvis types. The type you have may affect whether you can give birth vaginally.

Keep reading to learn more.

Generally speaking, genetics and environmental factors determine the overall shape of your pelvis. In the 1930s, two researchers divided the pelvis into four different types.

They largely based these pelvis types on the shape of the pelvic inlet, which is the upper area of the pelvic cavity. During vaginal childbirth, the baby passes through the birth canal, which runs through your pelvic cavity. The pelvic inlet is at beginning of the birth canal.

The four different pelvis shapes are:

  • Gynecoid. This is the most common type of pelvis in females and is generally considered to be the typical female pelvis. Its overall shape is round, shallow, and open.
  • Android. This type of pelvis bears more resemblance to the male pelvis. It’s narrower than the gynecoid pelvis and is shaped more like a heart or a wedge.
  • Anthropoid. An anthropoid pelvis is narrow and deep. Its shape is similar to an upright egg or oval.
  • Platypelloid. The platypelloid pelvis is also called a flat pelvis. This is the least common type. It’s wide but shallow, and it resembles an egg or oval lying on its side.

Remember that these pelvis shapes are more like guidelines as opposed to rules. Pelvis shape can vary greatly among females around the world.

Now let’s talk about how the different types of pelvis shapes can affect childbirth:

  • Gynecoid. The gynecoid pelvis is thought to be the most favorable pelvis type for a vaginal birth. This is because the wide, open shape give the baby plenty of room during delivery.
  • Android. The narrower shape of the android pelvis can make labor difficult because the baby might move more slowly through the birth canal. Some pregnant women with an android pelvis may require a C-section.
  • Anthropoid. The elongated shape of the anthropoid pelvis makes it roomier from front to back than the android pelvis. But it’s still narrower than the gynecoid pelvis. Some pregnant women with this pelvis type may be able to have a vaginal birth, but their labor might last longer.
  • Platypelloid. The shape of the platypelloid pelvis can make a vaginal birth difficult because the baby may have trouble passing through the pelvic inlet. Many pregnant women with a platypelloid pelvis need to have a C-section.

In the past, doctors used X-rays to determine the shape of a pregnant woman’s pelvis. While this typically isn’t done anymore, your doctor will still examine your pelvis to get an idea of how it’s shaped.

Another thing to keep in mind: Though the overall shape of your pelvis doesn’t change, hormones released during pregnancy cause some of your pelvic joints and ligaments to relax. This helps with labor and delivery.

Your pelvis and the surrounding tissues have evolved for pregnancy and childbirth. Plus, other factors besides pelvis shape can influence whether you’re able to give birth vaginally. These include situations where:

  • the position of your baby is abnormal, such as feet first (breech) or sideways (transverse)
  • you’re carrying multiples
  • your cervix doesn’t dilate enough
  • there are dangerous changes in the baby’s heart rate (distress)
  • the baby’s umbilical cord is compressed or prolapsed
  • there’s a problem with the placenta, such as placenta previa
  • you’ve had a C-section in the past

The pictures below can help you better visualize the different pelvis types. The pelvic inlet marks the beginning of the birth canal.

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Four common types of female pelvis shapes. Illustration by Diego Sabogal

Several health conditions can affect your pelvis and the surrounding muscles. Some examples include:

  • Pelvic floor dysfunction. This is when the muscles of your pelvic floor have trouble coordinating to help you go to the bathroom. It can lead to incontinence and pain in your pelvis or lower back. Pregnancy is a common cause.
  • Pelvic organ prolapse. Prolapse can happen when the muscles of your pelvic floor weaken. As a result, pelvic organs — like your uterus — can drop or even press out of your vagina. Common causes are childbirth, menopause, and aging.
  • Sacroiliitis. Sacroiliitis is when the joint that connects your pelvis to the lower part of your spine becomes inflamed and painful. It can happen during pregnancy or due to an injury or arthritis.
  • Osteitis pubis. Osteitis pubis happens when the joint in the front part of your pelvis becomes inflamed and painful. It’s often caused by repeated stress to the area through activities like playing sports.
  • Pelvic fractures. This is when there’s a break in one of the bones of your pelvis. Pelvic fractures are often caused by injuries or accidents. Some may require surgery to repair.

If you’re pregnant or planning to become pregnant and have concerns about how your pelvis shape might affect childbirth, speak with your doctor. They can examine your pelvis to help get an idea of how it’s structured.

Remember that many other factors besides the shape of your pelvis can affect whether you give birth vaginally. As with the type of pelvis you have, many of these things are out of your control.

But you should make an appointment with your doctor if you experience any of these symptoms:

  • pain or pressure in your pelvic area that’s persistent, recurring, or interfering with your daily activities
  • problems with urinary or fecal incontinence
  • pain that happens during sex, while inserting a tampon, or while using the bathroom
  • feeling like something is coming out of your vagina or seeing something bulging out of your vagina

While pelvis shape can vary widely among females, there are four general types: gynecoid, android, anthropoid, and platypelloid. The shape of your pelvis may affect whether you can give birth vaginally.

The gynecoid pelvis is the most common pelvis shape in females and is favorable for a vaginal birth. Other pelvis types, such as the android and platypelloid shapes, may lead to a more difficult vaginal birth or the recommendation of a C-section.

But pelvis shape alone doesn’t determine how you give birth. Other factors, such as the position of the baby or if you’re carrying multiples, could also lead to your doctor recommending a C-section.

Regular checkups and communication with your doctor are an important part of promoting a healthy pregnancy and delivery. Always attend all of your prenatal appointments and never hesitate to talk to your doctor if you have any questions or concerns about your pregnancy or delivery.