Small Pelvis? Big Baby? Here’s The Truth About CPD

Small Pelvis? Big Baby? Here's The Truth About CPD

“You’re really small. Are you planning a c-section?”

“Your baby bump is huge! Looks like a big baby is on the way. Are you sure he’ll fit?”

If you’re on the petite side, or if you’re expecting a larger baby or if you’re a first time mother-to-be, you might hear a great deal about babies being too big to fit through the pelvis or birth canal.

When a baby cannot fit through the pelvis, this is called cephalopelvic disproportion (or CPD for short). While we might hear this term every now and again, true cases of CPD are actually pretty rare.

In the 18th and 19th century, poor nutrition that resulted in rickets, and illnesses such as polio, lead to pelvic anomalies. These pelvic anomalies made CPD a somewhat common occurrence — one that resulted in loss of life during childbirth. As our nutrition and lifestyle have improved, pelvic anomalies have become rare.

Today, true cases of CPD are few and far between. In nearly every birth, the pelvis loosens and moves to make room for baby.

In the few cases where CPD does occur, it’s often the result of congenital abnormalities or severe injuries, for example, a pelvic fracture during a traffic accident.

If CPD Is Rare, Why Do We Hear About It So Often?

Unfortunately, while our lifestyle helped to reduce the rate of pelvic anomalies, our birth culture shifted to non-evidenced based practices.

These non-evidenced based practices led to many implied cases of CPD making it seem like a common concern. These implied, not truly diagnosed cases, are usually the result of other things like failure to progress, which is often simply failure to wait.

If you’re concerned about CPD, know that research has shown that it’s nearly impossible to diagnose CPD before labour has been well established. Unless you have a pelvic injury or congenital abnormality, it isn’t even easy to predict the risk of CPD before labour.

If there are sound concerns about CPD, waiting for spontaneous labour isn’t generally contradicted. In this case, you can go into labour naturally, and mother and baby can benefit from knowing baby is ready to be born.

With everything we hear about babies “not fitting”, it can be hard not to be concerned.

Here are 3 things you should know about birth and CPD:

#1: Neither Your Pelvis Or Your Baby’s Head Is A Fixed Object

The pelvis is not one solid bone. It is made up of several bones held together by ligaments. During pregnancy your body releases the hormone relaxin. Its release causes your ligaments and joints to loosen to facilitate baby’s movement through the birth canal. This hormone is why you might experience joint weakness and discomfort towards the end of pregnancy.

Baby’s skull is made up of separate bones that allow their head to mould and fit through the birth canal. These separate, not yet fused, bones is why babies have ‘soft spots’ known as fontanels.

#2: Your Position Makes A Big Difference

Being on your back or being in a semi reclined position during birth can narrow pelvic measurements by 30%! When you’re giving birth, 30% can make quite the difference. Squatting, side lying or being on all fours can create optimal space for baby to descend.

#3: Baby’s Position Is Important

Babies are designed to descend and navigate through the birth canal. They are an active participant in birth, moving and flexing through your pelvis. Occasionally babies are not in an optimal position making labor difficult, and sometimes making it impossible for baby to navigate the birth canal. In many cases, different things can be done to encourage optimal fetal positioning to facilitate a vaginal delivery. If baby simply can’t get into a proper position, a c-section might be necessary. In this case, a proper diagnosis of mal-positioning and not CPD can help mamas plan for a future VBAC.

Does A Previous Diagnosis Of CPD Mean Repeat C-Section?

Many cases of CPD are actually implied and not properly diagnosed. Reviewing your medical records and discussing them with a healthcare provider can help you understand why CPD was suspected.

In the absence of pelvic abnormalities, being that the pelvis isn’t a single fixed bone, it can have varying measurements from one birth to another.

Knowing the position of the baby can also help in understanding why labor didn’t progress. Did baby have any bruising or molding that indicated their head was tilted or flexed? What position were you in while laboring and pushing?

Stories Of CPD Experiences From Australian Midwives:

“I met a woman who told me she had had a caesarean section for CPD with 1st bub. Had a homebirth with 2nd, who was 2lb heavier. I believe CPD does occur, but is very rare.”

“Not really a story, but a lot of the cases of ‘CPD’ where I work, I notice the babies either have asymmetrical moulding, or bruising that is not right where it should be. Most of these babies are asynclitic presentations, it seems, and are being labelled as CPD, scaring the women into future caesarean sections without the facts.”

“There is a dishonesty and lack of true understanding of the abilities of women’s bodies, let alone birth, by those who readily use terminology like CPD to justify forceps and vacuum deliveries, not birth, in this instance! Where is the logic that the head will only fit when pulled out?”

If you’re concerned about CPD, here are some tips:

#1: Choose A Healthcare Provider You Trust

When deciding the type of healthcare provider you would like to work with, private midwife, midwife or obstetrician, ask questions. Find out how often they diagnose CPD, how they handle subsequent pregnancies after CPD and if they frequently diagnose CPD during pregnancy. Their answers can help you understand what kind of care you might expect. If they diagnose CPD often and before labor begins they might not be using evidenced based practices for diagnosing CPD.

#2: Learn About Optimal Fetal Positioning

As mentioned, baby’s position is important. While most babies get into proper position without any aid, occasionally some will settle into difficult positions. Our more sedentary lifestyle (most of us no longer walk and squat frequently throughout the day) can also lead to baby being posterior which is face up, instead of anterior which is facing mama’s spine. Reading the link above regarding optimal positioning is very helpful.

#3: Take An Independent Childbirth Education Class

Taking a childbirth class that builds your confidence, provides you with evidenced based information and portrays birth as the normal body process that it is, can help you prepare for a positive birth experience. When you know ways to prevent implied CPD, when you know signs of true CPD, you are better prepared to have a positive birth experience regardless of how labor unfolds. You will have the information and tools necessary to make informed decisions about your care.

#4: Hire A Doula

Having a doula improves birth outcomes. Antenatally, your doula provides you with evidenced based information and helps to build your confidence in your ability to give birth. You also have the emotional security of knowing you will have constant support. Many doulas can aid in facilitating optimal fetal positioning and encouraging your to give birth in an upright position. Both of which can help avoid a misdiagnosis of CPD.

#5: Get Another Opinion

If your provider mentions CPD during your first pregnancy, or you’re planning a VBAC after suspected CPD, seek a second (or even a third, or fourth) opinion. You deserve a provider that will listen to your concerns and one that uses evidenced based practices. If you’re feeling unnecessary pressure to plan for a c-section, get another opinion.

What If My Ultrasound Shows a Big Baby?

Ultrasound can be a wonderful diagnostic tool, but as with all things it has its limits. Ultrasounds are generally accurate for dating and measurements in the first trimester, but towards the end of pregnancy the accuracy is much less. It is important to note that the Australasian Society for Ultrasound in Medicine in their policy, ‘Statement On Normal Ultrasonic Fetal Measurements,’ states the following: “No formula for estimating fetal weight has achieved an accuracy which enables us to recommend its use.”

Recommended Reading

Read more about CPD and find links to CPD-related studies here.

Watch me!

A great clip on YouTube from ICAN about CPD:

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Maria Silver Pyanov is a mama of four energetic boys and one unique little girl. She is also a doula and childbirth educator. She's an advocate for birth options, and adequate prenatal care and support. She believes in the importance of rebuilding the village so no parent feels unsupported.


  1. Hello, your recommended reading and research link on the bottom of this blog redirects back to this exact page. When presenting this information to clients, it would be helpful to have actual studies cited within your blog and links to the history of cpd. I love this write up, I just need evidence based links to prove it to others. Thank you.

      1. Hi there
        The link still links back to the blog post. I would LOVE to use this in my studies for research papers (I am in an OB rotation in nursing school), but I can’t without citations and sources. I hope you’re able to post it.

  2. Yesterday I assisted a woman giving birth to a 5410 grams baby. Labor was induced because of the estimated fetal weight. It was her second delivery, the first being 10 years ago and of normal weight. When my shift started, my colleagues wished me luck and made some remarks expressing their fears, relieved their shift had ended. I understand, but it also irritates me, when people are being so pessimistic and full of fear up front. Let’s just see how it goes, and let’s try not to worry until it’s necessary. Of course I know the risks and I’m on my guard, looking for the signs, but unless I see such signs I’m optimistic.
    She soon reached full dilatation, but without urges to push. She was complaining she couldn’t find a position she was comfortable in, so I suggested to her to lay on her side – that wasn’t it – standing – that didn’t do it for her either – sitting on the toilet – but still she wasn’t comfortable… She said she wanted to lay flat on her back. I was a bit stunned… and a bit on guard because of what it could do to the baby’s oxygen supply, but given the fact we were monitoring the baby anyway, I agreed to give it a try. Bingo! She was finally comfortable and the baby was fine with it! Now she wanted to push and she did an excellent job! She pushed for 68 minutes when the head was born up to the eyebrows. I was trained to deliver the baby within the same contraction the head is born (15 years ago), but I know better now, thanks to international colleagues. Fearing dystocia didn’t make it easy on me to keep calm and wait, and then the fetal heart rate dropped to 60, making it even harder to calmly wait for the next contraction – I calmed myself knowing that the baby’s heartrate had been splendid until that moment, so we would have some time. The next contraction came, the head slowly came, it slowly turned and only then I helped the shoulders by moving the head down a bit. No dystocia at all. The signs of distress quickly faded as I dried and stimulated his body on his mothers belly, without a need for extra oxygen or extra care. Within half an hour he latched onto his mothers breast.
    A glorious victory!
    My advise: never act out of fear.

  3. I am 5ft 4, & 57kg (pre-preg) 2 days ago I had my beautiful bonnie 9lb 11oz boy!! We had a quick 2hr labour, and he was born at home!! I had a small graze. I was so worried about his size but he came out fine!! Just believe in your body and your baby, you can do it!!!

  4. I am 5’1″ and birthed 2 babies over 8 lbs 1oz. Pre pregnancy, I was a size 5, 138 lbs after my first son was born my hips expanded up to a size 12 and 157 lbs right before childbirth. The woman’s body can transform for child birth. I’m amazed that my body went through that much of a change, just for childbirth. I’ve noticed that when a woman’s pelvis goes through this drastic change, that most women restrict the pelvis ability to expand for clothes preparation for childbirth. I mean come on, I went through 7 sizes for childbirth! Your body knows what to do, don’t restrict it..

  5. I am a midwife and practiced squatting from 1985 when I started midwifery until 1992 when my first baby was due. I had a posterior, 4kg baby and laboured for 24 hours before being caesared for deep transverse arrest at 8cms. I was active during labour and kneeled over a bean bag on the floor until being talked into an epidural after 15 hours, so I did not lie down until then. I am 5ft 2 in (158cm) height and my husband was 6 ft 3 (195 cms). After I had my daughter, they wanted me to have a pelvimetry to get an idea of the size of my pelvis for hte next baby, which I didn’t do and regret. The next baby was a boy and I knew he was bigger so asked my obstetrician if I could still try for a natural delivery as I thought I would have a chance if he was anterior. As I couldn’t be induced due to a previous C/S, I waited and waited to go into labour, but his head was so big (37cms) that it didn’t even enter into the pelvic inlet, let alone go through the pelvis. He was 4835 gms! So, even though I know that it is the excuse used many times for unnecessary c/s, I know that I certainly did have true CPD.

    1. I did also. You would never think it by looking at me but my baby girl ended up being an emergency csection after 17 hours of labor. I could feel her there, I was fully dilated and the top of her head could be seen but she just could not pass and eventually went into distress. Scary for a first time mother. My son 14 years later was a scheduled c-section.

  6. I had my two boys through c/s because of the same case of small pelvis. The first one,the Dr did not even allow me go into labour nd the 2nd one,the baby was actually bigger,I got into Labour,but the Dr said the baby’s head was not descending. He said it’s only if the baby weighs like 2.5kg downwards that it can pass through my pelvis. I’m now pregnant nd worried. Please what can I do to avert another c/s? Thanks for your concern.

  7. My daughter recently went through labor and her provider did not correctly diagnose CPD and the baby died. Just because it is rare doesn’t mean it doesn’t exist. I believe in birth options. I also believe it is in every baby’s birth plan to be born alive.

  8. My concern is for my daughter who is at 38 weeks and the baby is large as shown through sonogram. She has always had small hips and now a huge belly and is concerned about labor. Her provider is at a naval base and she is not sure if he has diagnosed CPD. She has been told by someone (related by marriage) who says also has small hips and has had four children with no problem and “all women have the same equipment ” so not to worry.
    When my daughter was born, she had myconian fluid and her head was placed in an oxygen (bubble) and IVs in her head – my labor over 24 hours as I took very long to dialate. What advice should I be giving my daughter?

  9. Although I’m sure it’s over diagnosed it is possible. I’m 5’0 and had a C/S with my daughter after laboring for 17 hours because I never dialated. Her shoulders got stuck at my hip bones. She was only 6lbs. With this baby he is measuring in the 50th percentile and he isn’t even able to be head down and engaged. He is crookade and his head is near my left hip. Apparently my hips turn inward a little so my kids can’t fit through at all.. my daughters shoulders had bruises and her head was bruised because of her resting right on my bones. So I wasn’t as crazy as I thought! I’m 34 weeks with this one and pretty miserable. Excited to meet him none the less!

  10. Great article. My wife had two emergency c-sections after attempting vaginal deliveries. Our eldest was breached and had a very large head and weighed 8 lbs, 10 oz,, the OBGYN stopped the vaginal labor for an emergency c-section baby was distressed. He was born healthy, via c-section. Our daughter was in position, weighed just north of 7 lbs, larger head, wife was in labor 30 hours after her water broke. My wife fully dilated but our daughter’s head would not fit through her pelvis. She became very distressed, heart rate dropped really low several times, they put an oxygen mask on my wife, and for hours we had a team of RNs and the OBGYN’s concerned faces to stare at periodically, this OBGYN was very committed to a VBAC but warned that the baby was at risk if we continued as she was extremely stressed “she is not going to fit” and I strongly recommend a section delivery asap. I okayed the emergency c-section when the baby’s heart beat was fading, a special pediatric ER team was called in as a precaution, I was in the OR, baby was born not breathing or moving, with a very low heart beat, color was way off. It took the Pediatric team 2 minutes of resuscitation to get my baby responsive, another hour for her temperature to hold, her Apgar was a 1 (since she had a low heartbeat she got her only score that wasn’t a zero). Scariest moment of my life. A member of the pediatric team came to me after 30 minutes of the birth, I thank her for saving my baby, she said… “I’m not going kid you, she had all of us very concerned, she was very distressed but she’ll be alright now”. Our daughter is 1yr 4 months old now, healthy with no lasting effects from her rough start.

    We still recommend VBACs to our friends, but the OBGYN told my wife that she will not be able

    A little bit of background: wife is very healthy, organic diet, home cooked meals, gym 5 days a week, 5’3″ with small hips, currently weighs 123 lbs. She’s in her late 30’s. I am 6’3″, 205 lbs, healthy, larger head size. I was born via c-section, my mom had 3 emergency c-sections, also small pelvis and large babies with larger heads (she was 4’11” and weighed 120 lbs when she became pregnant with me, I weighed 10 lbs at birth with a huge head) I was born back when c-sections were rare here in the US, less than 10% of deliveries and Mom was in labor for 40+ hours. Genetics play a role in all of this.

  11. I totally agree. My first baby and second were c sections. Narrow pelvis and large babies will do that. Had long labour with first then felt awful felt wonderful after second which was planned. Good for u.

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