A wet nurse is a woman who breastfeeds and cares for another woman’s child. For most of human history, this was the only alternative when a mother couldn’t produce enough milk, died in childbirth, or was otherwise unable to nurse. The practice shaped families, economies, and infant survival for thousands of years before the invention of commercial formula made it largely unnecessary.
How Wet Nursing Worked
The arrangement was straightforward in concept but complicated in practice. A woman who was already lactating, usually because she had recently given birth herself, would nurse another family’s baby. In many cases, the wet nurse moved into the hiring family’s home and became a live-in caretaker. This created an uncomfortable reality: to feed a wealthier family’s child, a wet nurse often had to abandon or wean her own infant. The role offered income to women with few economic options, but the cost was deeply personal.
Wet nursing appeared across nearly every culture. Ancient Egyptian, Greek, and Roman families employed wet nurses. European aristocracy relied on them for centuries, partly because frequent breastfeeding suppresses fertility, and noble families wanted to produce heirs quickly. In colonial America and throughout the era of slavery, enslaved Black women were forced to serve as wet nurses for white families’ children. The practice carried different social meanings in different places, but the biological function was always the same: keeping an infant alive when its mother’s milk wasn’t available.
The Biology Behind Breast Milk Production
Lactation normally starts through a hormonal chain reaction during late pregnancy. Estrogen, progesterone, and a hormone produced by the placenta prepare the breasts to produce milk over the final months. At delivery, estrogen and progesterone drop sharply, which allows prolactin to rise and trigger actual milk production. The baby’s suckling then maintains the supply through ongoing hormonal signals.
What makes wet nursing biologically possible is that any lactating woman produces milk with the same basic nutritional profile, regardless of whose baby is feeding. A wet nurse didn’t need any special preparation. She simply had to be already producing milk, which meant she had either recently given birth or was actively nursing her own child.
It’s also possible to induce lactation without pregnancy, though this requires significant effort. According to the Mayo Clinic, the process involves hormone therapy to mimic pregnancy’s effects on breast tissue, followed by regular pumping sessions that gradually increase in frequency. The pumping schedule typically starts at five minutes three times a day and builds to 15 or 20 minutes every two to three hours, including overnight. Success isn’t guaranteed, and the process demands considerable dedication.
Why Wet Nursing Disappeared
Three innovations in the 1800s made wet nursing obsolete for most families. First, animal milk (particularly from cows and goats) became a more common substitute in a practice called “dry nursing,” which flourished in the 19th century. Second, the rubber nipple, invented by Elijah Pratt in 1845, made bottle feeding practical for the first time. Baby bottle designs multiplied during the Industrial Revolution.
The final blow came from commercial formula. In 1867, German chemist Justus von Liebig created the first commercial infant food, a powder made from wheat flour, cow’s milk, malt flour, and potassium bicarbonate. By 1869, his product was selling in American grocery stores for $1 a bottle. Nestlé followed in the 1870s with its own formula at half the price. For the first time, families had a shelf-stable, affordable alternative to human breast milk. The need to find, hire, and house a lactating stranger evaporated.
Modern Equivalents: Milk Sharing and Donor Banks
Wet nursing in the traditional sense is rare today, but the underlying idea, giving a baby someone else’s breast milk, is alive and well. The practice now takes two main forms: formal milk banking and informal milk sharing.
Formal human milk banks collect, screen, and pasteurize donated breast milk, then distribute it primarily to hospitals for premature and sick newborns. The World Health Organization recommends donor human milk as the preferred alternative when a mother’s own milk isn’t available for low-birth-weight infants, placing it above formula in the feeding hierarchy.
Informal milk sharing is a different story. Tens of thousands of peer-to-peer milk exchanges happen each year through Facebook groups and other online networks. A national survey of milk sharing participants found that as many as 64% of respondents had obtained donor breast milk informally. Researchers now use the umbrella term “lactation surrogacy” to describe the full spectrum, from traditional wet nursing to milk kinship traditions in Islamic cultures to modern internet-based sharing.
Some parents also practice “cross-nursing,” where friends or family members nurse each other’s babies. This is essentially wet nursing on a smaller, more casual scale, and it happens more often than most people realize.
Safety Concerns With Shared Breast Milk
The risks that concerned families centuries ago still apply today, though we now understand them in biological terms. Breast milk can carry infectious agents, and unscreened milk from a stranger is a gamble.
HIV transmission through breastfeeding is the most commonly cited risk, though the actual danger from a single exposure is extremely low. The CDC notes it is unaware of any documented case of HIV transmission to a child from a single exposure to another mother’s milk. For mothers on antiviral treatment with undetectable viral loads, the transmission risk through breastfeeding their own infant is less than 1%. Hepatitis B and C are unlikely to spread through breast milk unless blood is present.
The more practical risks with informal sharing involve bacterial contamination and tampering. Studies have found that a significant number of informally shared breast milk samples were colonized with disease-causing bacteria, including gram-negative bacteria and coliform bacteria. Some samples have been found diluted with cow’s milk, which infants under one year can’t properly digest. The FDA, the American Academy of Pediatrics, the American Medical Association, and the European Milk Bank Association all discourage informal milk sharing and recommend using regulated milk banks instead, where donors are screened and milk is pasteurized.
Regulated milk banks eliminate most of these concerns through donor health screening, lab testing, and pasteurization. The tradeoff is access: milk banks prioritize medically fragile infants, which is part of why informal sharing persists. Parents who can’t get banked milk and don’t want to use formula turn to online communities, accepting risks that medical organizations consider unnecessary.