[12.20.2023] Updated content, AnKing Overhaul for Step 1 & 2/AnKingMed, ID 939876

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For context, AMBOSS says 7% (https://next.amboss.com/us/article/a40Q3T?q=neonate%20weight%20loss#w8XhK-)

Looks like this was changed to 10% in UWorld though based off the old table in Additional Resources that claims 7%

@herstein.jacob can you double check uworld step 2 7726

Loss ≤10% of birth weight is physiologic in the first week of life; weight should be regained by age 2 weeks. Management is reassurance and monitoring. Excessive weight loss (>10% of birth weight) with signs of dehydration may prompt further intervention (eg, formula supplementation, serum electrolytes)

Being nitpicky but could the difference be in defining physiologic weight loss in the first 5 days vs the first week (7 days)? 7% being normal in the first 5 days and up to 10% in the first week, would make sense mathematically if we average it to 1.5% per day

Nice catch, AMBOSS cites a book from 2016 for the 7%, i wonder what UWorld cites and whether we should keep as is or change text to first week

AAP textbook says “The full-term healthy newborn may lose 5% to 10% of birth weight in the first few days.” AAP public website says >10% in 3-5 days is excessive. I think 10% in 7 days is much cleaner, but not sure if there is rationale for saying 7% in 5 days instead (newborn visits are usually 2-5 days after discharge?)

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Might be that 7% is normal (mean value), but >10% is abnormal / concerning. The study UW quotes mentions the mean weight loss was 6.3%. Support changing to 10% given the text says “up to”, could say in extra that amboss says 7% is normal (slightly different meaning) @anking-maintainers
Amboss: “Loss of up to 7% of birth weight in first five days of life is normal”


Think that looks good!

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@AnKing-Maintainers please vote, would be nice to cloze this one out


can we consider >7-10% as abnormal
and in the extra we can explain the differences between AMBOSS and UW

Okay with adding an explanation to extra field, would prefer to stick with 1 number in text though so it’s easier to remember


nice pun

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I am inclined to favor UW and change, but this 7% in 5 days rule is direct from AMBOSS q-bank (see below)… not sure what the best course of action is. Maybe something like this?

Healthy infants may lose up to {{c1::7}}% of their birth weight in the first 5 days of life, or {{c1::10}}% in the first week

“A weight loss of < 7% is normal in exclusively breastfed neonates in the first five days of life. The weight loss is the result of reduced intake and urinary excretion of excess fluid. This patient’s physical examination findings are consistent with those of a healthy newborn (e.g., soft anterior fontanelle, moist mucous membranes, capillary refill time < 2 seconds); therefore, breastfeeding can be continued. The weight is then gained back by the age of 10-14 days by drinking breast milk and/or formula. This patient has only lost ~ 5% of weight, which is still well within the normal limits.”

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like 1 number personally, but okay with both numbers in text. Both UW and Amboss questions are about a child with 5% weight loss so should still get answer correct. Could also just add a note to extra that UW says 10%

idk if if it’s helpful to you but
UTD says in one article they lose 7-10% of their weight
And in another article it says up to 10%

If anyone has access to the AAP’s Textbook of Pediatric Care, ch. 207 on weight loss should give a definitive answer. My school’s library links me to the book, but then says subscription doesn’t cover it.

I was reading through this article in amboss and it actually says that they might lose up to 10% in if they are breastfed, 7% in formula "
*Breastfed infants may lose up to 10% of birthweight *
Formula-fed infants may lose up to 7% of birth weight. "


Why not go with 10% and say the threshold might be lower in formula fed babies!


Good find! Would support that, seems like that is likely why the numbers vary