False Negative Hydrostatic test in a live born foetus may be seen in:
The hydrostatic test is false negative (the expanded lungs may sink) due to atelectasis, diseases like acute oedema, pneumonia, congenital syphilis, etc. Ref: The Essentials of Forensic Medicine and Toxicology By Narayan Reddy, 27th Edition, Page 384
Atelectasis
Aificial Respiration
Emphysema
Putrefaction