Ultrasound and Baby's Weight

Jane Foley's picture


Dear Ms. Ultrasound,
I had a regularly scheduled ultrasound last week and the doctor took some measurements of the size of the baby's abdomen. He seemed to be taking longer than usual on that one particular body part and I started to worry. Sure enough, his diameter measurements of the abdomen were predicting that the baby was in the 7th percentile of growth. He told us that 10% was the cutoff and anything lower meant there could be problems. Naturally I started to worry that it would be something very bad and I haven't been able to shake this idea that there is something wrong with the health of the baby.

We have had a chromosomal scan and the odds came back 1 in 2000. We also had an anatomical scan that indicated everything was perfect. These results are doing little to help me relax.

The other thing he did ask is whether I was certain of the accuracy of my ovulation date (based on LMP). I have a notoriously irregular cycle, so I natural said no. He said his regular scans all along have been putting me at slightly less than the LMP based on a 14 day ovulation would suggest. During this particular scan that concerned me, he noted that the computer scan was putting me at 30 weeks when we thought I was at 31 weeks. He said that this could be a reason why my baby was measuring small. I go in for another scan in five days (ten days from the last scan).

Do I have reason to hope that everything is fine with the baby but I am just not as far along as we thought thanks to a later ovulation? Anything you can say to help me prepare would be great.

Worried in Mexico


Hello, You should not worry! A difference of 1 week in the second trimester is NEVER cause for concern.

The measurements can be up to 2 weeks off and still be normal. Look at the differences in baby size when they are born. They can be 6lbs to 9lbs. All normal.

I give you permission to stop worrying immediately!

With regards,
--Jane RDMS