Big baby dropping percentiles

[Hannahthepink]

When DS was born, he was an unexpected whopper at 10 pounds 6 ounces. He is now 7 weeks old, and despite feeding well, looking healthy, being content and alert, he is gaining weight slowly and is now just in the 25th percentile.
The health visitor looked surprised as he seems perfectly healthy and strong otherwise.
We actually talked about whether his weight at birth could have been 'pumped up' by sugar or fluid or something and he is finding his true weight.
Does anyone else have any experience of this happening to a large birth weight baby?

Is he now maintaining that line?
What gestation was he born on? Did you have fluids during labour?

It's a bit early to tell whether he's maintaining a line I guess, he's gaining as opposed to losing weight, but it just isn't enough, so the line he's making is pretty flat instead of curving upwards like they want him to be!
He was born at 40+11, I did have fluids during labour (not sure how much, but an IV line). Scans measured average size, fundal height pretty normal, GD negative (but my theory is that I developed it late on and it was undetected leading to big baby).

The fact that he was born post dates and you have fluid I think increase the likelihood that his birth weight was 'overinflated' IYSWIM (as of course would GD). There's some research which points to it being better to weigh babies 24 hours after birth as this gives a more realistic baseline. Are you and your DH very tall or average? Genetics is a factor too.

DS1 was a shade under 9lbs at birth (and 40 + 12 so a little under 75th centile) and very quickly fell to 25th. But he was late, I had fluids in labour and with parents who measure 5'7" and 5'4", 25th centile was about right! Of course if you're both over 6 ft it's a bit different!

Thank you, yes, we are both very average sized, no giants in the family!

I'm trying to relax about him 'catching-down', which seems to be a very real thing, but largely overlooked by HPs.