Final answer:
Breast size before pregnancy does not determine the amount of milk they produce during lactation; this is a false statement. Milk production is influenced by suckling which stimulates hormones like prolactin and oxytocin, not the amount of fatty tissue in the breast.
Step-by-step explanation:
The belief that breast size before pregnancy determines the amount of milk they produce during lactation is false. Milk production does not depend on the size of the breasts, which are comprised of mammary glands and fat tissue. The mammary glands themselves are responsible for milk production, and each gland has 15 to 25 lobes, with ducts that empty at the nipple. It's the suckling of the baby that stimulates the release of hormones such as prolactin and oxytocin, which in turn promote milk production and release.
The mother's mammary glands undergo changes in the third trimester to prepare for lactation and breastfeeding. The amount of fat behind the glands determines breast size, but this fat does not influence milk quantity. Instead, the regular removal of milk by the baby through suckling is what maintains prolactin levels, keeping milk production up.