In the early 1990s, major professional societies—including the American College of Obstetricians and Gynecologists, the American College of Physicians, and the American Heart Association—recommended hormone replacement therapy for all postmenopausal women, based on studies that showed it prevented both osteoporosis and heart disease. A decade later, as widespread use failed to produce the predicted cardiac benefits and unanticipated harms occurred, the recommendation was withdrawn.

In July 2002, the results of a large study were published that showed that women who took HRT were more likely to develop breast cancer. They also had a higher incidence of heart attacks, strokes, and blood clots. Nearly everything that health care providers had believed about HRT was disproved.

It was a formative experience of my career. How did good people with good intentions get things so very wrong? They made a mistake common in the field of preventive health. They based their recommendations on small, early studies that showed benefits without waiting for larger studies to demonstrate that the benefits were real, and that no risks had been overlooked. Even the professional societies failed to wait for definitive evidence.

We don’t seem to have learned from that debacle. In fact, we are currently engaged in repeating it. In this case, the practice being aggressively promoted is breastfeeding. Every major professional organization and society, from the World Health Organization to the American Academy of Pediatrics, insists that breastfeeding has significant health benefits for babies, that increasing breastfeeding rates will improve infant health, and that breastfeeding save lives.

In 2010, breastfeeding advocates confidently predicted that raising breastfeeding rates would save lives, reduce disease, and lower health care costs. Nearly nine years later, none of that has come to pass, even though the breastfeeding rate in the U.S. has almost quadrupled—from 22 percent in 1972 to over 83 percent in 2015. That should not come as a surprise. There has never been any proven association between breastfeeding rates and infant health: Many countries with very high breastfeeding rates have high rates of infant mortality, and many countries with low rates of infant mortality have very low breastfeeding rates. That’s just what you would expect if breastfeeding had very little impact on infant health.

Breastfeeding may be right for some babies and some mothers; it was right for my four children and me.

There are benefits to breastfeeding, of course. These include a small protective effect against colds and diarrheal illness across the population of all infants in their first year. Breastfeeding has also been associated with a lower incidence of sudden infant death syndrome, though it’s worth noting that pacifier use reduces SIDS risk even more. The biggest benefit of breastfeeding is found in extremely premature babies. For this population, breast milk seems to lower the incidence of a severe complication known as necrotizing enterocolitis (NEC). When extremely premature infants have been fed with breast milk, they have experienced measurably fewer instances of NEC.

On the other hand, it is becoming increasingly clear that aggressive breastfeeding promotion has significant risks. There has been an increase in babies falling from their mothers’ hospital beds or suffocating. There has been a rise in serious harms to babies including dehydration, starvation, brain injuries, and even deaths. Indeed, exclusive breastfeeding on discharge is now the leading risk factor for hospital re-admission. This is exactly the sort of risk that is extremely difficult to account for in a small study, but is essential to consider when assessing the overall benefit of a policy. This is particularly important when the known benefits for most babies—slightly fewer colds and cases of diarrhea—are so minimal.

Aggressive breastfeeding promotion is not only harmful for babies, it can be harmful to mothers. First, breastfeeding like any other natural process has a failure rate. For example, 20 percent of pregnancies naturally end in miscarriage. It should therefore not be surprising that up to 15 percent of first-time mothers will not be able to produce enough breast milk to fully nourish an infant, especially in the first few days after birth. The relentless emphasis on exclusive breastfeeding instead leaves frantic new mothers to cope with starving babies who won’t sleep because they are so hungry. Second, some women can’t or do not wish to breastfeed. Constantly admonishing them that they are depriving their babies of important advantages (that don’t actually exist) leads to needless feelings of guilt and shame and can potentially exacerbate postpartum depression.

Nearly a dozen papers published in the past five years have revealed these harms. And yet, the conventional wisdom that “breast is best” prevails. Again, how have good people gotten things so very wrong? There are three reasons.

1. Nearly all benefits of breastfeeding come from extrapolation of small studies that have never been replicated at larger scale. This is the same thing that happened with hormone replacement therapy.

2. Breastfeeding is closely associated with higher socioeconomic status. That means the benefits we’ve attributed to breastfeeding may actually accrue from greater wealth and better access to health care, not from breastfeeding itself.

3. White-hat bias, a cognitive bias promoting what are believed to be righteous ends, pervades breastfeeding research. It’s a particular problem here because of how breastfeeding intersects with formula use. In the 1970s, formula companies convinced some African women to stop breastfeeding and use formula instead, arguing it was healthier. The result was disastrous: The contaminated water used to prepare the formula sickened and killed babies. (This risk is why breastfeeding really is a legitimate recommendation to enforce in areas with contaminated water.)

The formula companies’ action was both unethical and inexcusable, but the result was not merely appropriate disgust with manufacturers but inappropriate demonization of formula itself. Today, white-hat bias leads breastfeeding researchers to avoid any conclusion that recommends formula and might thereby enrich its manufacturers.

Those who promote breastfeeding as “best” are trying to do the right thing, just as those who promoted HRT as life-saving were trying to do the right thing. Yet just like with HRT, large-scale implementation of the recommendations did not produce the benefits claimed, and in fact revealed risks they did not anticipate.

In the case of hormone replacement therapy, providers turned on a dime; they immediately stopped recommending HRT. Sadly, breastfeeding researchers have responded much differently. Most have actually dug in their heels and vilified anyone who dares to question breastfeeding’s benefits. It’s only a matter of time before they are forced to acknowledge that the benefits of breastfeeding term babies in industrialized countries are so small as to be undetectable and the risks are so significant that we should stop aggressively promoting breastfeeding.

Breastfeeding may be right for some babies and some mothers; it was right for my four children and me. But we must stop pretending breast is “best” when the latest research shows that it is often not the case. Otherwise breastfeeding will become the new hormone replacement therapy. That’s a debacle we should fear to repeat.