Clinical meaning
Lochia is the vaginal discharge that occurs following childbirth, composed of blood, decidual tissue (the endometrial lining that supported the pregnancy), white blood cells, mucus, and bacteria. This discharge is a normal physiological process that reflects the healing of the placental attachment site on the uterine wall. During pregnancy, the uterus enlarges from approximately 60 grams to nearly 1,000 grams at term. After delivery of the placenta, the process of involution begins -- the uterus contracts and progressively returns to its pre-pregnant size over approximately 6 weeks. The placental site, which was richly vascularized to support fetal circulation, now represents a large wound approximately 8-10 centimeters in diameter on the inner uterine wall. Hemostasis at this site is achieved primarily through myometrial contraction, which compresses the spiral arteries that previously supplied the placenta. These uterine contractions, often called afterpains, are the primary mechanism preventing postpartum hemorrhage. Oxytocin released from the posterior pituitary gland (and administered therapeutically) stimulates these contractions. The lochia progresses through three predictable stages that reflect the healing process: lochia rubra (red, blood-heavy discharge occurring days 1-3 postpartum),...