Pregnancy period minimum

Patient: Hello i stated havin intercourse with my wife on 20 december and she gave birth to a 3.7 kg daughter on 9 august how is that possible. i have been avoiding to have this conversation with my wife not to offend her but i have strong feelings thats not my child, i dont know if its a coincidence the child looks different from the other and this has been affecting me for the past 14 years.

Symptoms: Pregnancy