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Sway Back Adjustment on Undies


Today, I’m showing you a super simple pattern alteration that I’ve carried over from “normal” garment to lingerie – a sway back adjustment.

Sway back adjustment? Say whaattt?? If you have never heard the term – it is an exaggerated inward curve at the lower back waist, right above your… I’ll keep in PG and not say ass on the blog… woops! Right above your buttocks is what I meant to say. If you’ve ever had a dress pool and wrinkle across the back like the first two images in this post, then you need a sway back adjustment. I was a gymnast, and I am now a total yogi, so I always make this adjustment if a garment – dress, blouse or pant – is close fitting in that area.

I have a standard high-waisted underwear pattern that serves as my block, but since lingerie is extremely fabric dependent, I know that I will have to “scoop out” the center back at least somewhat depending on the amount of stretch it has. Don’t know what I mean? Hopefully, you’ll understand once I go through the steps below.

The first step is to make the pair of underwear in the final fabric. Because undies take up so little fabric, I don’t worry too much that it might go to waste. Then, I try on the undie and pin out the wrinkles that are pooling at the center back, which usually tapers to nothing at the side seam.

Then, I measure the amount I pinned out and transfer it to the pattern. How do I do this? On the pattern, I measure down from the original center back waistline equal to the amount I pinned out (remember to double the number since you pinned on the fold!). Using a French ruler, I draw a line to the top of the side seam. Make sure that the line is perpendicular to the center back for about a ½” or else you’ll get a point. Last, I align the front and back undie patterns together at the side seam to make sure the waist line transitions smoothly from center front to center back. All of this is illustrated in the graphic above.


  1. Reply


    I’ve been very swayback my entire life and have been sewing about as long. My experience is not all but most who believe they need a swayback adjustment really need to let the hips out so the fabric can fall as it needs to. If the hip fabric is not wide enough it will sit on the back, above the booty and under the waistline. My recommendation would be to first let out the side seams to the waistline, see how much width is missing, make that adjustment, then decide if you still need a swayback adjustment and proceed….from a lifelong swaybacker.

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