This might be long, but I'll try to be quick...
My DD is 4 weeks old. She was 9.2 when she was born. Up until last week breast feeding had been going great, when we think she developed reflux. We went to the doctor, he put her on Zantac. She's been doing much better in the last few days.
When they weighed her at that appointment she weighed 9.10. She was in the 50 percentile, so he wasn't too worried, but wanted us to come back today to check her weight over the long weekend. She lost an ounce.
While I was pregnant they discovered early on that she had an enlarged kidney, which toward the end of my pregnancy seemed to have rectified, however, he took a urine sample from her today to check for a possible infection. Depending on the results from that we'll schedule her 6 week ultrasound sooner. It's possible that a bladder infection might cause poor weight gain, but he's doubtful since she has wet diapers, eats well, etc etc.
Anyway, we go back next Monday for another weight check. If she hasn't shown any marked improvement he mentioned supplementing with expressed breast milk and/or formula. That makes me sad. He is really good about helping me breast feed, but if she is loosing weight then she needs the calories from somewhere. He's also really good about finding out the underlying cause, hence the urine sample and ultrasound.
So, what can I do to get her to gain weight? What could also be the cause? I so desperately want to avoid supplementing with formula.