Alterations

Dear Carol,

Unfortunately, most of the manufacturers of denim or jeans for women do not design the pants to fit a woman's figure. For almost all women no matter their size and shape their buttocks protrude much more compared to their waist. This is why we get the gap at the back of the pants.

If the designers of women's jeans place darts in their block patterns and then transfer it into the yoke seam line, the jeans would fit women's bodies much better.
Bellow I will explain how you can fix this problem in a few different ways.

1) Re-sewing the flat felt seam evenly
You can use ladder stitches (15. Ladder Stitch Basting) to baste the seam from the right side of the pants. Start at the waistline and baste about 3 cm past the end of the gaping fabric. Make sure the stitches are about 1 cm in length, to keep the pieces together better when we remove the top stitch lines.

Now when you remove the top stitch lines in this area, the pieces will not fall apart. This way you will also have the reference seam line for taking in the excess fabric.

After basing the excess fabric we do a fitting to make sure it fits well, before finishing the seam using the flat felt seam style (8. Sewing Flat Felt Seams or Blue Jean Seams (Self Finishing)).

2) Gaping at the back of the pants
If the gap is not too big, you can take in just from the center back seam, without affecting the look of the center back seam.

Otherwise If the gap is larger and only on the yoke. You can sew two waist darts about 7 to 10 cm from the center back seam, to get rid of the gap.

However these darts should not have very large intakes because they are short and end before reaching the yoke seam.

Usually for those with a very small waist circumference we take in from the center back seam and sew in two waist darts as well.  We may also consider sewing two darts on either side of the center back seam of the yoke. Giving us a total of four darts in the back.

3) Taking off the waistband
In case you need to take in from the center back, the excess waistband length at the top of the center back seam can be removed by adding a seam at the center back of the waistband. Then re-sewing the belt loop in place

Sometimes when the waistband is large, we can take in the waistband at the side seams. However we need to have enough excess fabric for the seam allowances. This way you can avoid moving most if not all the loops.
Other times we may want to take in from the side seams and the center back, you can take off the waistband along the back, passing the side seams by a few cm towards the front. Then take in all the excess length of the waistband from the center back.
To do this, you need to remove the center back belt loop, and sew it back latter. The side belt loops on the back can stay on at the top and be undone at the bottom to be re-sewn in place again after taking in the side seams of the pants. This way the front of the waistband will stay intact.

Thanks,

Nehzat