#AllButtsWelcome: Unmentionables: Crotch Variation in Pantie Fitting

This is a tale of my search for fit and adjustment to panties in order to make a pair that fit me, and in the process discovering the neglect of variation in the shape of the bony pelvic girdle, and how this affects pantie fit (or lack thereof).

Pencil sketch of a person picking a wedgie with the text "instagram.com/kate.harrison.art" written over it
Figure 1. ‘Wedgie’ © Kate Harrison (used with permission)

Ready-to-wear (RTW) panties ride up my butt, and the leg elastic sits on my labia. As a result they are extremely uncomfortable, and like the men who are always shifting their nuts to get comfortable, I am always pulling my panties out of my crotch. When I finally solved the fitting riddle, I told my daughter of my joy in having panties to wear that were comfortable and they fit right so I was not constantly aware of them. I was astounded when she told me that she just gets rid of any panties that are uncomfortable, as I all the panties I had ever bought had ridden up to give me constant wedgies.

I started searching online for how to fit the gusset or crotch, but came up empty. Timelace Studio’s 2016 post on ‘How to draft a basic panty pattern’ was typical of what I found, in that it worked off the assumption that all panties have same gusset length and width. Like most guides I found, her pattern was drafted off only four measurements, while others use five.

Diagram showing different places to measure around the hips and crotch
Figure 2. Standard fitting measurements

The measurements required were:

  1. Waist circumference;
  2. Hip circumference;
  3. Waist to hip at side seam; and,
  4. Seat height.
  5. Crotch length – included in some instructions

Measurement that were specified as staying the same through all sizes were:

  • Gusset length = 14 cm (The gusset length stays the same trough all sizes)
  • Front gusset width = 8 cm (This measurement stays the same through all sizes)
  • Back gusset width = 11 cm (This measurement stays the same through all sizes)

As I suspected my fitting issues were with the gusset, instructions that assumed all gussets had the same width and length were problematic. Equally problematic were pantie drafting instructions that said: copy a pair of well-fitting panties. If I had a well-fitting pair of panties I would not have bothered making them. One of the problems I had was that no one could suggest a starting point for measuring or adjusting a pantie pattern for better fit in the gusset.
Many blogs recommended Beverly Johnson’s Craftsy Class ‘Sewing Panties: Construction & Fit’ as the best place to learn about fitting panties, so I signed up. Beverley Johnson includes pantie drafting instructions in her class, but the gusset length was specified as a fixed ratio to hip circumference, and the gusset width as the same 8 cm for all sizes. Beverley had no advice other than trial and error in response to my question about gusset fitting, so I finally jumped in to try a pattern.

In early 2019 I decided to try House Morrighan’s recently released Clover Boybrief (HM-CBB). When I was fitting the HM-CBB measuring the gusset width with a tape measure didn’t work, as it is a dynamic space, changing shape as you move. A flat ruler won’t work either, as the fabric in the gusset has to wrap around the labia. As I expected to have fitting issues, I began with a muslin based on my waist and hip measurements, in size 6 graded to size 8 at waist of the high cut briefs in a horrible green mesh (with horizontal stretch only). It had all the fitting issues of my RTW panties, but I could pin out a tuck to reduce gusset length, and measured as best I could how much too narrow the gusset was. I made second muslin with shortened extra-wide gusset. The gusset had enough width for me to (carefully) mark the crease between my leg and pelvic floor with pins, take them off and measure how wide a gusset I needed. The adjustments were substantial, I had to reduce gusset length by 5/8” and increase width by 1¼”. Figure 3 shows the alterations I made to the pattern in red, and figure 4 shows the finished fit.

One of my problems in searching for information and in describing my fitting issues was the lack of a suitable terminology. I needed information about crotch fit — the length and width of the pelvic floor area between my legs. But when I searched crotch length I got results for the length from front waist through the legs to back waist, the measurement described as ‘crotch length’ in Figure 2. Figure 5 illustrates the physiological landmarks that provide stable reference points for measuring the adjustments I needed. The pubic bone marks the front of the gusset, the coccyx (or tailbone) marks the back, and the leg creases mark the sides. To distinguish the crotch measurement from the meaning of the standard sewing use of ‘crotch length’, I decided to describe the gap between the front and back bony landmarks as ‘crotch depth’. The gap between the fleshy landmarks created by the crease between the legs and the pelvic floor area I describe as ‘crotch width’, as it does not conflict with any existing sewing terms.

Figure with two images, one of hip bones and one of female genitalia with arrows highlighting different measurements
Figure 5. Crotch landmarks and measurement terminology

This terminology is consistent with standard terminology for 3-D objects, where the x-axis is referred to as ‘width’, the y-axis as ‘height’, and the z-axis as ‘depth’.

Digital skeleton with a 3-D graph next to it
Figure 6. Measurement terminology conventions (Remixed using skeleton by Bernhard Ungerer ‘3D Female Skeleton Anatomy’, 22 June 2008 (CC BY 3.0))

When I started this fitting journey, undie design seemed to assume a standard ratio between hip circumference, hip height, and crotch depth and width. I started thinking about how I could need such a substantial variation from standard sizing, and the simplest explanation was that my pelvis was wide relative to depth, which called into question the assumption of one size fits all for pantie gusset design.

To illustrate how the same circumference can be based on different width/depth ratios, I took photos of exactly the same loop of string stretched into a wide flat oval, a slightly rounded oval, and a very round oval (top photos in Figure 7, from left to right). For illustrative purposes, I then overlaid these ovals with identical size legs, and marked the crotch dimension. The bottom row of Figure 7 shows wide shallow crotch left (pink dashes), slight (average depth) crotch centre (red dashes), narrow deep crotch right (blue dashes). I then overlaid these crotch/gusset shapes on top of each other in Figure 7, bottom far right. Each pelvis has identical hip circumference, but very different crotch/gusset shape and dimensions. When designers assume one size fits all, only the centre oval gets fitted properly.

Figure with three different sized ovals on top and three combinations of ovals on the bottom along with different-sized crotch pieces superimposed on each other
Figure 7. Effect of varying pelvis width/depth on crotch dimensions and gusset fit.

Figure 8 is a diagram demonstrating initial proof of concept, with a gusset that is too long and narrow relative to pelvic floor dimensions. The leg seems to sit uncomfortably on the labia, and gusset is pulled up between buttocks in wedgie, which is exactly what I experience, as can be seen in Figure 9.

Failing to find information about crotch dimensions and fitting in the sewing community, I went looking for alternative sources of information about pelvic shape. It occurred to me that childbirth may have something to do with it, which sent me into the obstetrics literature, but what I found was that while childbirth widens the pelvis it doesn’t flatten it, and if that were the cause of my fitting problems, more women would report it as an issue. However, whereas the sewing community was silent on the issue of crotch variation, the obstetrics and midwifery professions took such variation as a given. When I started this fitting journey two and a half years ago, most of the obstetrics and midwifery literature I found based their identification of four types of pelvic shapes on 1933 research by Caldwell & Moloy. I have included Physiopedia’s ‘Pelvic Floor Anatomy’ in Figure 10 because it is a useful creative commons image that does not require permission to use, as long as you include (CC-BY_2.0) and source, but the article does not reflect the findings of much greater pelvic diversity in more recent research. Betti (2017 – figure 9) uses Moloy’s original 1938 figure (she said I could use it as far as she could determine, it was out of copyright), and the diagram is useful because it emphasises the variation in width of the pelvic girdle.

Betti links the distribution of maximum diversity in pelvis shape to population migrations, with those who’ve travelled least from our origins in Africa having the most variation, as each migrating population carries restricted genetic diversity compared to origin populations. She found tall thin people of African descent more likely to have narrow and deep pelvic girdles, and short stocky populations in cold climates had wide and shallow pelvic girdles. While Fischer & Mitteroecker (2015) also link height to pelvic shape, they describe pelvic girdle shape as a compromise between conflicting evolutionary selection pressures for a shape optimised for upright bipedal walking on the one hand, and a very different shape required to reduce risk of maternal mortality giving birth to large headed babies on the other. Short women are more likely to have wide pelvic girdles so babies can fit through them, not necessarily because of population migration and genetic constriction, but because of evolutionary pressure due to selective maternal survival of some shapes more than others.

Diagram with four different pelvis shapes labeled gynecoid, android, anthropoid and platypelloid
Figure 12. ‘Pelvic types’ Gail Tully@Spinning Babies

Figure 12 ‘Pelvic types’ from Gail Tully@Spinning Babies midwifery information site is the other image I found early on in my search for information. Once I got this far in my experimentation and research, I started to post my pantie makes and my thoughts, along with figure 11, and a rougher draft version of figure 6, on various FB sewing groups. I’m short, with a wide shallow pelvis, which according to these sources put me in the 5% minority of women who have Platypelloid pelvic cradles. This would make it not surprising it hasn’t been catered for by pantie designers. However, FB brings together thousands of sewers interested in the same thing, enough for quite a few to find it relevant to them.

In August 2019 Greenstyle Creation’s No Show Brief (GS-NSB) was released, and I made and adjusted a few pairs during Sharon Aguilar’s sew along, as it has minimal sewing, turned out to be super comfortable, and I could get two pairs out of a 1/4m of swim fabric – figure 14 shows the result. I’m including the gusset adjustments I made in figure 13, because it is a quite different block to standard pantie patterns. Having sorted out my fit adjustments on the HM-CBB, however, I was able to transfer them to these panties without difficulties. I shortened the gusset and increased the gusset width, adjusting the back leg seam to match the gusset width.

When I contacted Gail Tully@Spinning Babies in preparation for writing this blogpost, as well as kindly giving me permission to use ‘Pelvic types’ image in figure 12, she also drew my attention to recent research that rejects the idea ‘there are four distinct types of female pelvis’. Just as midwives need to be aware that pelvic shapes are distributed in a continuum, with many components that can vary in dimension independently from one another (Kuliukas et.al. 2019). Rather than being seen as distinct categories, one of which everyone will fall into, the four pelvic shape diagrams should be seen as ideal types — mental images that help us organise information, not reflections of reality (Harrison 2013) .

More recent research that makes distinction of pelvis types less clear cut, and which finds proportions of types vary across populations, makes it impossible to make generic claims about proportions of pelvic type. However, it is possible to say that most standard panties are designed for the 14% – 18% of women with a Gynecoid pelvis (Delprete 2017), which at best suits a minority of the population. The standard pantie may also suit the 51% – 59% of women with an Android pelvis, in which case they would fit up to ¾ of the population. However, the 20% – 23% of women with the deep narrow Anthropoid pelvis, and the 10% – 14% with the Platypelloid pelvis are left out in the cold.

While there seem to be far more complaints online and on FB about gussets that are too short and wide, than there are about gussets too long and narrow, this still means 30% – 57% of women have trouble with pantie gusset fit. In figure 7, I only altered one variable – pelvic width, while keeping other variables – hip and circumference and leg size, the same. In actual people, all these variables can change independently. This is why figure 5 suggests some ways of measuring key crotch dimensions to get a good gusset fit. What is needed are easy ways of measuring our crotch width and length so we can readily compare with and adjust the pattern. In March 2020 I raised this with Jennifer Fairbanks, @Porcelynne, on her FB group, and at that time she was in the process of editing her Bare Essentials underwear book, and she planned on incorporating the issues associated with gusset fit in the new edition.

Apparently the average adult person is between 2” and 3” in crotch width. In response to my post about this, someone on the Porcelynne FB group suggested measuring gusset width using fingers, as in Figure 12. Four fingers gives me 3”, but is not wide enough, I need to add a fifth finger from my other hand to reach across the width of my pelvic floor. This is potentially a simple way of determining width that gets the gusset width close to enough. If you cut your first muslin out with a slightly wider gusset, you can use pins to mark the leg crease more accurately. There is further progress in this space, as in mid-2020 Apostrophe released their custom draft MyFit Underwear, so it will be interesting to see how well their drafting algorithm works for all shapes of pelvis.

If someone else has already figured it out, let me know. Hopefully this tale will remind both designers of the fact that there are multiple dimensions in which pelvic girdle, and hence crotch shape can vary, and it will provide some tools to help pantie sewers of all shapes get a better fit.

Karey Harrison, feminist philosopher of science and linguistics, environmentalist, retired academic, home baker, sewist, gardener.
https://www.instagram.com/kareylea/ https://usq.academia.edu/KareyHarrison

A picture of the author wearing a cycling helmet, cycling glasses and a high visibility jacket.