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This is the the last part of the maternity swimsuit construction. Click for pattern alteration and the finished swimsuit. It’s basically like putting together a swimsuit with a couple extra steps. This is just my way of putting it together, if you know or think of something better, feel free to do it your own way.
First, cut out the pieces you need depending on what style you’re making. For the torso piece and bottom torso piece, cut 2 fabric pieces and 2 lining pieces.

Maternity Swimsuit: Growing Torso ConstructionMaternity Swimsuit: Growing Torso Construction
To start, first put in a stretch needle! This will keep your fabric from getting holes.
Then sew together the casing on the fabric and the lining at 5/8″. I sewed with a straight stitch because this piece doesn’t need to stretch as it will be gathered.
Maternity Swimsuit: Growing Torso Construction

With right sides together, the bottom torso piece can now be sewn to the torso piece.

Maternity Swimsuit: Growing Torso Construction

With a stretch stitch, sew the pieces together with the torso piece up, so that when you come to the casing you can leave two holes for the ties. Remember to backstitch well at each stop. I left 1/4″ holes.

This will leave two small openings at the bottom of the casing. Sew together to lining torso but don’t leave holes.

Maternity Swimsuit: Growing Torso Construction
Lay the fabric torso piece on top of the lining torso piece wrong sides together.
Maternity Swimsuit: Growing Torso Construction

Pin the lining piece to the fabric piece at the casing. Ignore my socked feet in the corner.

Maternity Swimsuit: Growing Torso Construction

I used a double needle for this next step but you can use a basic straight stitch if you like. I used the little screw in marker to find where 5/8″ should be. Then sew down both sides of the seam. You are creating the casing between the fabric and the lining because you want the lining to stretch like the fabric.

Maternity Swimsuit: Growing Torso Construction

Next, sew down the center seam stitching in the ditch. This separates the casing into two.

Maternity Swimsuit: Growing Torso Construction

Make two ties by cutting out the length you want by 1″. Sew with a stretch stitch at 1/8″.

Maternity Swimsuit: Growing Torso Construction

Turn them inside out.

Maternity Swimsuit: Growing Torso Construction

Using a safety pin or other threading tool, thread the ties through the two casings. You can put the ties in through the holes you left at the bottom.

Maternity Swimsuit: Growing Torso Construction

Sew the ties in at the top of the piece, so they are secure.

Maternity Swimsuit: Growing Torso Construction

I just knotted the ends of my ties to finish them. Feel free to do it however you like.

Maternity Swimsuit: Growing Torso Construction

Now pin the outsides of the piece together and serge or zigzag all the edges together.

Maternity Swimsuit: Growing Torso Construction

With wrong sides together, serge or zigzag the back piece together.

Maternity Swimsuit: Growing Torso Construction

Measure the side seam on the back piece. Mine is 13″.

Maternity Swimsuit: Growing Torso Construction

Cut out the side seam measurement from elastic. I like using clear 1/4″ elastic. It holds up the best in chlorine, and I love how thin it is.

Maternity Swimsuit: Growing Torso Construction

Pin each end to the side front.

Maternity Swimsuit: Growing Torso Construction

Find the center of the elastic and pin it to the center of the fabric. Keep doing this until the elastic is pinned about every 1 1/2″.

Maternity Swimsuit: Growing Torso Construction

Since I have 2:1 ratio, I have a lot of fabric to gather. If I were to do it again, I’d make it a smaller ratio to make this next step easier.
Starting in the middle use both hands to stretch the elastic to match the length of the fabric. I sewed with a wide long serpentine stitch, but you can use a zigzag stitch too. Don’t use a straight stitch.

Maternity Swimsuit: Growing Torso Construction

This is what it should like like when you’re not stretching it. See how the elastic gathers the fabric?

Maternity Swimsuit: Growing Torso Construction

When you get to the end, flip it around and finish the other edge.

Maternity Swimsuit: Growing Torso Construction

Using a zigzag sew the side front to the side back.

Maternity Swimsuit: Growing Torso Construction

Sew with the gathers up so you can make sure they’re staying even.

Maternity Swimsuit: Growing Torso Construction

Your front torso piece is done! Now the rest depends on what style you have for your swim suit. Mine is a basic top so I sewed the bodice to the torso.

Maternity Swimsuit: Growing Torso Construction

Make sure you secure the ties in the seam.

Maternity Swimsuit: Growing Torso Construction

Sew elastic onto the empire line seam.

Maternity Swimsuit: Growing Torso Construction

Secure the elastic down, by sewing with a double needle from the top.

Maternity Swimsuit: Growing Torso Construction

Once I had the basic swimsuit sewn together, I put on the suit and put in the bra cups where I wanted them.

Maternity Swimsuit: Growing Torso Construction
After you sew in the bra cups, you just need to sew elastic to the edges and finish the edge with a double needle. Then you have your growing swimsuit!
Let me know if this makes sense! I hope to see the suits you make!

Author: Heather