Devise a scenario after the Napoleonic Wars where the French birth rate and overall population growth increases allowing it to maintain parity with other contemporary European nations, or to regain its mantle as the "demographic beast" it was the 13th Century.

Would something like more industrialization and better sanitation help in this regard? What sort of economic or political developments would be necessary for this? How would this affect French colonial policy in the 19th Century?

Would something like a successful Talleyrand Plan (where France gains Wallonia in 1830), or the annexation of Belgium help in these regards?