Need to know if I change needle size when using worsted wgt

:waving: I have a question to ask : If your pattern calls for DK sports wgt. yarn and size #3 and #6 US knitting needles, but I have a lot of worsted wgt. yarn which I would like to use in this pattern, DO I CHANGE THE SIZE OF MY KNITTING NEEDLES TO SIZE #2 and #4 , beacuse worsted wgt. yarn is a little thicker then DK sports wgt. yarn, so in my way of thinking using the worsted wgt. yarn would make the sweater bigger. My pattern that I wish to use is The #1559 Sirdar baby wrap sweater pattern. sizes go from 0-3mos. to 5-6 years. I will be making a size 1 yr. as my new great-granddaughter born 1/24/07 weight in at 9lbs.11ozs. Big girl. Her name is Faith. I just joined this Forum today and so I am new at this. Hope I do it right. I am 72 years. old and have 3 gread-granddaughers and 2 great-grandsons. I would appreciate any help I can get with this problem. Have a great day.
New knitting buddy, Barbara J. :waving:

Your thinking is correct in that you’ll need to go down in needle size. First things first, you need to knit a gauge swatch to make sure your needle and yarn combination work to get the size you need.

Another important reason for knitting the swatch is that it will show you a sample of the finished fabric. When knitting a worsted weight yarn on small needles, the fabric can become tight and stiff, and not ideal for a baby item. But only your gauge swatch will tell… it may work, but it may not. You need to make sure before you spend all that time knitting.

Also, consider that sometimes you just can’t knit a worsted on small enough needles to get the correct gauge…

Another thing you can do is go up to size 6 and 8 and make a smaller size. Size 2 and 4 needles will make an awfully stiff and dense fabric with worsted weight yarn. Try out a sampler with all different sizes of needles and see which ones produce a fabric you like then go with those and adjust the pattern. As you know, babies only get bigger, so having it a little larger would work out all right.