An interesting question – and one which is not so easy to answer. The obvious symptoms of real pregnancies vary so widely within and between all breeds that there is no relative ‘gauge’. In addition, every dog’s phantom pregnancy is essentially different. However, differences are often exaggerated by the fact that behavioral symptoms in cases of real pregnancies last longer and are usually more pronounced. For example, the nesting instinct is usually maintained for far longer when the pregnancy is real. This may not just involve the actual nest-building but can be characterized by chewing on materials such as bedding for prolonged periods of time.