sewing a maternity swimsuit

How To Make "Cottesloe" Pattern Into Maternity Swimsuit

Ever since I got pregnant I knew I am going to be in my second and third trimester during summer time, and summer time in Israel is HOT! So I knew I need to find a good swimsuit. I started to look in local shops and online, and I realized there are so little variety of maternity swimsuit out there or very beautiful and very expensive ones… even though I have never sewn a swimsuit before I figured “I can do this!!” and lucky me for the timing because Megan Nielsen just released a new swimsuit pattern called Cottesloe!

Maternity swimsuit sewing tutorial
Cottesloe pattern view A
Maternity swimsuit sewing tutorial
Maternity swimsuit sewing tutorial

Although I had a good pattern to use I still had to figure out how to modify it to maternity use. And let me remind you I didn’t even sew a swimsuit in my life nor alter a pattern to fit anything. But- challenge accepted!

I looked online for help, as we all do, and came across some great posts! One of them by DIBY CLUB was perfect, just what I needed to understand what changes should be made in order to make a regular swimsuit pattern into maternity pattern. In that post I was introduce to how to grade a pattern, which means that if you fit into several sizes in the pattern you can alter it to fit your body shape. For example if you do not fit into just size M but you need the garment to be: size S in the bust, size M in the waist and size L in the Hip. Read this post by DIBY CLUB and this post by Cashmerette to learn more about how to grade between sizes in PDF sewing patterns. And I also recommend to try this post by cotton and curls she have a very good free maternity swimsuit tutorial.

Maternity swimsuit sewing tutorial
Maternity swimsuit sewing tutorial

I decided to make view A without a tie on the back (but I might add one because the back is a bit too open) and I added lining and shelf bra which are optional and comes with the pattern. For this option you will need to print only pages 1-28,30,40.

Video tutorial

This is when you should watch my video tutorial! I will explain more and you more details later in this post, but first you can watch and hear me explain how I modified the pattern to maternity. I think it is much easier to understand while watching a video about it.

Swimsuit Front

After I printed the pattern and taped everything together, I first graded the front piece to my size. You can see my measurements and the sizes I decided to use from the pattern. I used a 2 sizes bigger size for my growing boobs in the bust, and 4 sizes bigger in the front piece of the waist for my growing belly. As seen in the video I marked the sizes in each section and then tried to follow the line of the pattern (In the DIBY CLUB post there are great examples of that).

My Measurements:

23 weeks pregnant Pattern size
BUST 95cm / 37.4 inch 10
WAIST 85 cm / 33.4 inch 16
HIP 110 cm / 43.3 inch 14

My Pattern sizes:

Front Back
BUST 12 12
WAIST 18 16
HIP 14 14

After I graded the front piece, I added length to make a gathering for my pregnant belly. As recommended in the DIBY CLUB post I added 4” (10 cm) to the length of the front piece. Then I cut only the front piece (both main fabric and lining) and gathered it. you should gather a little bit more then you add, so I gathered 5” (12.7cm). There is a great quick tutorial in my video on how to gather fabric. I first gathered the fabric so I would know how much to add to the back piece and after gathering it was 0.8” (2cm).

sewing a maternity swimsuit
Final front side
sewing a maternity swimsuit
Getting ready to cut!

Swimsuit Shelf bra

The shelf bra was so easy to sew and add the swimsuit thanks to Meagan amazing pattern! The only thing I need to add here is that you should cut the shelf bra piece according to the measurements of the front piece. Just put them on top of each other (the paper pattern, not the fabric) and follow the size from the edge of the armpit down.

sewing a maternity swimsuit
Final shelf bra

Swimsuit Back

Just like we did to the front piece, you should first grade the pattern and then add the length. Pay attention that I only used waist size 18 in the front piece, since my back shouldn’t grow during pregnancy I used size 16 in the waist. And I added 0.8” (2cm) as I mentioned before to the length so the front and back pieces will match. You will know exactly where to add the length because Megan marked it already in the pattern- thank again Megan!

sewing a maternity swimsuit
Final back piece


Over all the sewing part was easy. The Cottesloe pattern is easy to understand and to follow. Even though it was my first time sewing a swimsuit I didn’t had any trouble what so ever 🙂 I highly recommend this pattern and I can’t wait to make another one!

Maternity swimsuit sewing tutorial
Maternity swimsuit sewing tutorial

If you have any thoughts or questions leave them in the comments below!

Thank you for reading!


How to make any swimsuit pattern maternity fit
How to make any swimsuit pattern maternity fit
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