What link is there between immobility and the complications of pregnancy?

What's causing it? Immobility of what: one part of your body or your whole being? Must make diagnosis then treat it. Suspect severe depression or stroke. Depression during or after delivery (post-partum) is part genetic predisposition, hormonal and early life experience. Professional help and medication is obligatory. Forget breast feeding and use medication as directed by the experienced professional treating you.
Increased DVT risk. Pregnancy increases the risk of a deep vein thrombosis (DVT) by a factor of about 30, over the baseline risk for a woman. Decreased mobility would further increase that risk.