As a Doula, Childbirth Educator and Holistic Pregnancy Bodyworker, there is hardly a week that goes by when I don’t hear from women or see comments online from women who are nearing the end of their pregnancy and are being told by Drs and Obstetricians that their baby is too big to be able to fit through their pelvis. Women are incredibly vulnerable to fear-based messaging during pregnancy because nobody wants to put their precious baby in danger, and so they will usually err on the side of caution, at the suggestion or recommendation from their Dr.

This fear mongering, often based on ultrasounds that can be up to 15% inaccurate (so an estimated 4kg baby could be just 3.4kg!), activates their dominant stress response of Fight, Flight, Freeze or Fawn (usually the latter if like most women, they have grown up to be a people pleaser or “good girl”). This continues the grooming process (which often starts with the antenatal testing process) to hand over their power to the “experts” who will then talk them into being induced early or undergo planned caesarean to avoid baby getting stuck – either with obstructed labour (when baby’s descent through the pelvis is arrested) or shoulder dystocia (when baby’s head is out and their shoulders get stuck), even if these inductions and caesareans are risky procedures in themselves! Once this “fear grooming” process in pregnancy occurs, it is much easier to keep the fear activated when the woman is even more vulnerable during labour and birth – leading to even more unnecessary medical interventions and a higher caesarean rate!

I am a petite 160cm / 5ft 3, and before both of my babies were born, I weighed about 50kg. Having been a doula for 3 years before having my babies and knowing what kind of model of care and birth I did (and didn’t) want, I planned homebirths for both of my babies. With a gestation of 41 weeks and 6 days for my firstborn baby, he weighed a healthy (approximately) 4kg – I say approximately because in our baby bliss we skipped having Jetsun weighed until day 2, which was 3.9kg.

But baby #2 was looking even bigger from the beginning of my pregnancy. My belly popped out super early and at about 12 weeks I remember crying to my husband that I knew I was carrying twins which terrified me – not about the birth, but about having 3 kids under 3 (my sister had twins with numbers 3 and 4, so she had 4 kids under 6, so my fears were well founded!). Fortunately for me, it wasn’t twins, I was just carrying a big baby. I remember as I approached my due date, I asked my private midwife if my baby was big and she just smiled with a twinkle in her eye and said bub was going to be a “healthy size”! If only all maternity care providers displayed this kind of trust and reassurance to their clients about baby size, we would be having far less anxiety, inductions and caesareans! (Side note: I am not sure if there is any research to support this but i hear from my homebirth midwife friends that planned home birthed babies are usually bigger on average because they are much less likely to be induced for perceived large size or post dates, compared to hospital babies!)

 

 

< At a gestation of 40 weeks and 2 days, Keanu ended up being a “healthy” 4.49kg who I birthed like a boss and didn’t even tear! I like to do a “humblebrag” to any pregnant woman or expectant dad who will listen that, given I had a pre-pregnancy weight of 50kg, I gave birth to a baby who was almost 10% of my (then) usual bodyweight. (Extrapolate that to the average woman’s non-pregnant weight of 72kg, and that would be around a 7kg baby! Not saying that would be possible, but it certainly makes food for thought!)

 

 

 

This brings me back to the question: How DO Babies Fit Through Pelvises?

Well this is a 3 way combination of the wisdom of hormones, flexibility and biomechanics of the woman’s body; the flexibility of the newborn baby’s head; and the wisdom of the mother/baby dyad’s blood circulation!

#1. When a woman is pregnant, she produces the hormone Relaxin, which allows the ligaments that hold her pelvic joints together to be extra stretchy. When she is in natural labour, this hormone is boosted, and when she is upright or on all fours (ie. not flat on her back with an epidural causing weight bearing on the pelvic bones that would keep them fused together!), her pelvis can open up to 28% larger ,as her pelvic ligaments stretch open at the Pubic Symphysis at the front, her Sacro-Iliac Joints at the diagonals, and her Coccyx swings outwards at the back. (See below for how you can do Pelvic Mapping* to measure your pelvic outlet!)

#2. The average newborn baby’s head circumference is around 34.4cm which is a diameter of 10.95cm, while the diameter of the cervix is around 10cm. So how does a bigger head get through a smaller hole? The skull plates overlap when the baby is coming through the cervix and vagina which reduces the head circumference by around 10%. (My babies both had 37cm heads so their head circumferences would have reduced by even more to fit through a 10cm hole!) This is why the baby’s head looks like a walnut when it is crowning, as the head’s reduced circumference causes folds in the extra available skin.

#3. Up to 1/3 of the baby’s blood supply is still in the mother’s circulation and placenta until after the birth, which would obviously reduce the chunkiness of the baby’s body as it comes through the mum’s body. (This is why we don’t want to clamp and cut the cord until after that blood supply has caught up to the baby after birth. Don’t forget to insist on delayed cord clamping in your birth plan! Wait for the cord to go limp and turn white – ie “Wait for White”, before clamping and cutting. Or even better, wait until after the placenta has birthed to ensure your baby gets every drop of their blood supply!)

Aren’t women’s bodies, baby’s bodies and how they work together during natural birth just AMAZING??!!

*Pelvic Mapping

It is important to know that prior to birth, a woman’s pelvis cannot be accurately measured or birth outcomes accurately predicted, either by Xray or during surgery, because of the intricate dance at play during birth, as outlined above. But you can do a rough guesstimate of your pre-labour pelvic outlet by Pelvic Mapping, and extrapolate how that may expand during labour.

I pay homage to ex homebirth midwife Lisa Barrett, who taught me this measuring technique at a homebirth conference workshop years ago. It was a really fun workshop that was full of laughter as all the birth workers got into awkward positions measuring their pelvic outlets, and it has helped me demonstrate this valuable exercise to many of my doula clients who cannot fathom how they will birth their “watermelon sized” babies through their “lemon sized” holes. (And that is the last time I will ever mention lemons and vaginas in the same sentence. In the words of the famous American midwife Ina May Gaskin: “Your body is not a lemon!”).

1. Using a measuring tape, measure from the inside of the subpubic arch (at the front wall of the vagina) to the tip of your coccyx. Draw a vertical line onto an A4 piece of blank paper of the same measurement – given when you measure this on your body it is curved, it will be longer than if you were able to measure it through your tissues without the curve, but give the coccyx swings out during labour, the real measurement will increase in length anyway!

Whatever direction your heels are going will have a direct influence on how wide apart your sit bones or Ischial Tuberosities are, which (if your Sacrotuberus Ligaments which join them to your coccyx are not overtight), will allow them to move apart to birth your baby. Play with this concept by finding your sit bones and feel the difference in space between these bones by moving your heels in to “plié”, and out to “pigeon toed”.

2.  With this in mind, get your feet into pigeon toed / heels out position which opens the outlet, bend over a little, and measure between each sit bone, (get a partner to help you if this is physically awkward for you to do on your own, and not too socially awkward for you and your partner to do together!). Draw a line with this measurement on your A4 paper, crossing over the vertical / front to back line so that the diagram looks like a crucifix.

3. Draw an oval shape encompassing each point to demonstrate the length and width of your pelvis. I also draw a parallel line around the outside of the width to show how the pelvis opens up to 28% larger during labour when the woman is upright or on all fours!

The example on the right is a Pelvic Map (not to scale, of course) of my own (non-pregnant) pelvis. The same one that birthed a 4.49kg baby with a 37cm head through it – photo of that above!

I hope this article helps build confidence for anyone who doubts their ability to birth their babies, however big they are perceived to be!