Like most new parents, I was bombarded with advice when I had my first child. Relatives, friends, parenting books, and the ever-present internet (on your phone! While nursing!) all chimed in with conflicting shoulds and shouldn’ts for getting my baby to sleep, eat, learn, and stay safe.

How’s a new parent to sort all this? Many rely on their doctor for a final word—a sensible strategy. But as a family doctor myself, I have always been more skeptical of medical advice. That’s because, like new parents, doctors are overwhelmed with information. So we often rely on guidelines from professional organizations for information on what we should recommend to our patients. In the case of advice for new parents, this tends to come from the American Academy of Pediatrics. Sometimes this is great, because some of the AAP’s recommendations are based on mountains of data—for example, that childhood vaccines save lives. But sometimes, these recommendations are based on no empiric evidence at all.

Take infant sleep, for example. I thrived during long hours of medical training, but my newborn son reduced me to a whimpering mess in two sleepless nights. Curled on my bed, I whined, “Please, just shut up!” when he began bleating again.

We eventually settled into a routine: I nursed him or paced the house with him until he fell asleep. It worked until a sanctimonious parenting book, citing the AAP, told me I was doing everything wrong.

The AAP tells doctors to teach parents at the 1-, 4-, and 6-month-old visits that they ought to put their infant to bed “drowsy but awake.” This way, the baby learns to fall asleep on his own. Somehow I’d missed this lesson in medical school, which must mean I am both a terrible physician and a terrible mom. (Exhaustion does not help me put things in perspective.)

Later, I looked it up. “Drowsy but awake” has never been studied on its own. Dozens of trials have combined it with other sleep advice: swaddling, scheduled feedings, day and night routines, etc. A review of all studies on infant sleep interventions since 1993 showed no substantial benefit to any of the sleep programs. A separate meta-analysis, a powerful type of study in which data from similar trials are combined, came to the same conclusion. (This does not address sleep “training” of babies older than 6 months—other studies have found different results for them.)

In other words, there is no evidence supporting the recommendation the AAP gives. These findings liberated me. With my second baby I did whatever I wanted—if he fell asleep while nursing, fine. If I needed to put him down and let him cry for a few minutes, fine. And as a doctor, I started to simply reassure parents that it gets better. Most childhood sleep problems are temporary.

So why does the AAP make the “drowsy but awake” recommendation? Dr. Joseph Hagan, an editor of the guidelines, cites expert opinion. “If you talk to specialists who see 12-, 15-, 18-month-olds with sleep problems … there is a huge overrepresentation of babies who never were given the chance to be put down on their own,” he said. “Is that evidence? Well, sort of. We’re trying to avoid a bad outcome.”

This certainly sounds logical: Soothing an infant to sleep all the time could make it more difficult for the infant to self-soothe later. But the causality might also work in the other direction: Difficult toddlers may have been difficult infants. Without data, we can’t know.

In the end, this AAP recommendation isn’t based on data, it’s based on expert opinion. And expert opinion has an important but controversial role in medicine. Some groups, like the United States Preventive Services Task Force, don’t use it at all when they make recommendations. And some groups do. There are benefits and drawbacks to each approach.

Consider how the AAP and USPSTF approach the prevention of cavities in children. Cavities are caused by bacteria, particularly Streptococcus mutans, which digest sugar into acid. This acid erodes tooth enamel, eventually leading to cavities. Parents transmit the bacteria to their children; many of our kids have permanent Strep mutans colonies before they even have teeth. The way to fight these bacteria is to arm your teeth with fluoride: Whether from toothpaste, tap water, or direct application, fluoride decreases cavities by making tooth enamel more resistant to bacteria and acid. There’s plenty of evidence for this. And both the AAP and the USPSTF recommend fluoride to prevent cavities.

The USPSTF stops there. But the AAP offers four more recommendations: no bottles in bed, regular dental visits for parents, no sharing spoons or pacifiers, limits on sugar. I remember photos from medical school of teeth rotted from “night bottle mouth.” Theoretically, milk from a bottle, or from breast-feeding, pools in the mouth of a sleeping baby and provides an all-night buffet for Strep mutans.

So when a friend admitted that she didn’t brush her 2-year-old’s teeth, I tried to reassure her. “It’s probably fine. It’s not like you guys sent her to bed with a bottle or anything. That’s the worst thing for cavities.” My friend looked at the floor, and I realized I’d backpedaled off a cliff.

“We had to put her to bed with a bottle,” she explained. “It was so hard to get her to go to sleep otherwise.”

In fact, most American parents have given their baby a bottle in bed. It turns out that this may not be tragic: A comprehensive review did not find a consistent link to cavities. An examination of 2,400 children in Arizona found that tooth decay was more common only when kids slept with a bottle past the age of 2. They found no link for younger children.

Milk and formula just don’t have that much sugar. Nighttime bottles with juice, and sugary snacks during the day, are far more closely linked to cavities than a nighttime bottle with milk. Sugar is a real problem, but the USPSTF doesn’t have limits around it. Their standards are so high that in order to make a recommendation about sugar, they wouldn’t just need proof that sugar causes tooth decay: They would also need to know that counseling parents about it is associated with a demonstrable decline in cavities.

This level of evidence just doesn’t exist. Few clinical trials include children, so for most pediatric topics, the USPSTF feels it cannot weigh in at all.

The AAP fills these gaps, which may be useful for some parents. But what I think might be even more useful for all parents would be if the AAP would label which recommendations are backed by firm evidence, and which aren’t.

Hagan explained that it doesn’t do this because “if we were going to give a star for evidence, there would be very few stars.” That doesn’t sound great, but he also stressed that “we have really done the due diligence to come up with the strongest evidence-informed recommendations that we possibly can.”

Still, I believe that patients (and doctors!) deserve to know this distinction. Recommendations backed by weak evidence are more likely to be reversed down the road. As David Grossman, a pediatrician and vice chairman of the USPSTF, explained, “It’s really important for patients to understand where we’re on firm ice and where we’re on soft ice. … If you recommend something based on weak or insufficient evidence, you might find yourself, five years later, having to flip.”

Just look at peanuts. The new fourth edition of the AAP’s Bright Futures guidelines reverses its previous advice about preventing food allergies. Instead of delaying these foods—which was never supported by strong evidence—parents are now encouraged to introduce them early.

As doctors, we hurt our credibility with patients when we flip stances. We also hurt our bond with vulnerable new parents when we tell them that they’re doing something wrong, which makes it all the more important that we reserve that conversation for when we know we’re right. When I talk to parents, I try to remember the sinking feeling I had when I read “drowsy but awake” and the embarrassed glance from my friend when I shamed her about her daughter’s bedtime bottles. Maybe the guilt is a mom thing, but I think it’s a big deal.

Unanimously, the physicians I spoke with stressed the unique value of the doctor-patient relationship. As Bill Phillips, a family physician and former member of the USPSTF, put it, “These recommendations are not the most important part of medical practice … the most important is spending time with the patient, listening, and asking open-ended questions.” He thinks the biggest harm of weak guidelines is the time they take from “talking about something more important.”

I now save my parenting advice for just a few things that have strong evidence or particular relevance to a family. Otherwise, if a parent asks, I give the AAP’s guidance plus my interpretation of the evidence. This often involves a smile and a shrug, and I move on to reassure them that they’re doing a great job with their child.