topic Re: Birth weight for gestation (z-score for sex and gestation) in Statistical Procedures

Birth weight for gestation (z-score for sex and gestation)

Azertix — Fri, 13 Aug 2021 08:22:53 GMT

Dear team and users.

I am working on a study about babies that have to follow the EFSA guidance

https://efsa.onlinelibrary.wiley.com/doi/full/10.2903/j.efsa.2017.4779

In this guidance, it is asked to calculate “Birth weight for gestation (z-score for sex and gestation)” i.e. the Z-score at the birth of the baby based on the gestation duration.

I do not find a SAS macro that do that job. Do you know if this macro exist?

Precisions:

-For Z-score of anthropometry during life (Weight-for-age z-score, height-for-age z-score etc.) I have used the macro %igrowup_standard that come from the Who http://www.who.int/childgrowth/software/en/ ) but it does not work for “Birth weight for gestation”.

-I have find an excel tools that can do the job in theory for “intergrowth21”

https://intergrowth21.tghn.org/intergrowth-21st-applications/ but I am supposed to word in SAS a much as possible.

Thanks to who can help me. 🙂

Re: Birth weight for gestation (z-score for sex and gestation)

mkeintz — Fri, 13 Aug 2021 08:47:16 GMT

I take it that "gestation" is just a time variable, presumably in weeks.

If so, then why can't gestation be used as the age measure in the macro %igrowup_standard, which you report works for " anthropometry during life", and birth weight as the anthropometric measure?.

You say "it does not work for “Birth weight for gestation”. Why? Does %igrowup_standard require repeated measures?

Re: Birth weight for gestation (z-score for sex and gestation)

Azertix — Fri, 13 Aug 2021 09:05:36 GMT

@mkeintz :

Thanks for your suggestion.

Yes I can use %igrowup_standard to calculate Z-score at age = 0 but this does not take into account if the gestation time is 37 week or 38 or 39 or 40.

If I use %igrowup_standard whith age = 40 my baby will be compared to babies of 40 weeks, not with babies just born after 40 weeks of gestation.

No %igrowup_standard does not requiers repeted measures.

Re: Birth weight for gestation (z-score for sex and gestation)

ballardw — Fri, 13 Aug 2021 15:01:08 GMT

Do you know of a data set with the mean and standard deviation of any measure by sex and "weeks of gestation"? That would be needed to calculate a z-score.

I would ask whoever gave you this project where that data set resides.

Re: Birth weight for gestation (z-score for sex and gestation)

Azertix — Mon, 16 Aug 2021 08:01:59 GMT

@ballardw :

You are right. I actually only need a table of means and standards deviation by sex and gestational age. If I get this, coding the Z-score in SAS will be easy.

However, I do not find that with google. So I have ask just EFSA directly.