Handwashing is the most effective postpartum care measure in preventing infection because it directly reduces the transmission of pathogens from healthcare providers and the environment to the mother. Proper hand hygiene interrupts the chain of infection, significantly lowering the risk of puerperal sepsis and other postpartum infections. Unlike antibiotics, which are used selectively and can contribute to resistance, handwashing is a universally applicable, low-cost intervention that effectively minimizes exposure to infectious agents. Early ambulation and iron supplementation do not directly impact infection control.

Reference: Williams Obstetrics, Cunningham et al., 26th Edition.