Cookies for breakfast, staying up late and maybe a little more television than usual.

For some families, what happens at grandma's house stays at grandma's house.

But for others, clashes over parenting choices and enforcing parents' rules can cause major strife between a child's parents and grandparents, a national poll suggests.

Nearly half of parents describe disagreements with one or more grandparent about their parenting, with one in seven going so far as to limit the amount of time their child sees certain grandparents, finds the C.S. Mott Children's Hospital National Poll on Children's Health at Michigan Medicine.

Disputes most commonly involve discipline, meals, and TV/screen time. Other thorny subjects: manners, safety and health, bedtime, treating some grandchildren differently than others and sharing photos or information on social media.

"Grandparents play a special role in the lives of many children and can be an important resource for parents through support, advice and babysitting. But they may have different ideas about the best way to raise the child and that can cause tension," says Sarah Clark, M.P.H., Mott Poll co-director and research scientist with the Susan B. Meister Child Health Evaluation and Research Center, or CHEAR.

"If grandparents contradict or interfere with parenting choices, it can have a serious strain on the relationship."

The nationally representative survey is based on 2,016 responses from parents of children ages 18 and under.

Here, Clark discusses more of the poll findings and suggestions for families.

Addressing unmatched discipline styles between parents and grandparents

Among parents who report major or minor disagreements, 40% say grandparents fit the classic mold of being too soft on the child. But 14% say grandparents are too tough.

Nearly half of parents say disagreements arise from both styles.

"Parents may feel that their parental authority is undermined when grandparents are too lenient in allowing children to do things that are against family rules, or when grandparents are too strict in forbidding children to do things that parents have okayed," Clark says.

Many social norms around parenting have changed over the years, and grandparents may not be aware of current standards for how children speak or dress. In addition, parents now make decisions that grandparents did not face, such as when and where children use cell phones and other electronic devices.

Parents may want to explain to children why grandparents don't always follow the family rules, Clark says. When grandparents are being too lenient, this can be as simple as saying something like, "Grandma and Grandpa don't get to see you very often, so they like to pack all the fun things into a short visit."

But it can be trickier when grandparents are too harsh. Parents should first look for a way to calmly but firmly speak out to the grandparent, so the child feels supported. Later, parents can offer a longer explanation to the child, such as "When Grandma and Grandpa were your age, this is what parents did when children misbehaved. We don't do that in our family, but sometimes Grandma and Grandpa forget that things have changed."

Confronting a generational divide in parenting styles

"That's not how we did things and you survived" may be a common refrain for some grandparents who raised children when there were fewer research-based recommendations around parenting, such as car seats, introduction of new foods, spanking, screen time and sleep safety.

But when it comes to safety and health, parents may need take a hard stance. It may be helpful to point to newer research on children's health, such as putting babies to sleep on their back, wearing helmets while riding bikes and scooters, and using age- and size-appropriate car seats.

"Grandparents may have a hard time understanding why parenting and medical advice has changed so much since they raised children," Clark says.

She recommends parents consider inviting grandparents to a pediatrician visit or sharing articles from parenting magazines or websites to help grandparents feel more up-to-date and involved.

Setting boundaries with grandparents

Many families rely on grandparents for childcare and especially in these cases, parents should talk about expectations from the start.

They should decide what their deal breakers are (i.e. car seats, food choices) and be clear with grandparents that these are non-negotiable.

"When you hire an outside babysitter, it's straightforward to discuss parenting rules.  With family there are different dynamics; you're worried about hurting Grandma's feelings," Clark says.

"It may be more convenient to avoid the hard conversations when you're asking for help. But if you don't set clear boundaries from the beginning, it's much harder to correct later and can build mutual resentment."

MORE FROM MICHIGAN: Sign up for our weekly newsletter

Unsolicited advice may also feel like stepping over the line when it happens often or in a critical way.

Parents may respond with telling them they appreciate their expertise or "I know you may see it differently, but I'd appreciate it if you would do it this way when you're watching the kids. It's important to us."

Finding the common ground between parents and grandparents

Parents also need to be flexible in some areas. Occasionally letting grandparents bend the rules may be OK depending on how often they see them and as long as children are still safe and in a healthy environment.

Clark notes that while consistency is usually helpful in parenting, it's fine to make exceptions for special situations, or special people.

"Some grandparents look forward to the chance to 'spoil' grandkids and enjoy being 'softies,'" Clark says. "They may see this as a rite of passage and part of what makes the relationship special."

"Obviously there are extreme cases where differing styles may be problematic, especially if they affect children's behavior at home. If so, families should address these issues. But it's also OK if grandparents don't do everything the same way as parents."

Preventing conflicts from deteriorating family relationships

At times, the issue of grandparents flouting family rules may become too big for parents to ignore. But grandparents' receptivity to being asked to conform to parenting choices and household rules may vary from family to family, the Mott Poll finds.

When disagreements about parenting have occurred, 43% parents have asked a grandparent to change their behavior.  And nearly half of these parents say grandparents complied.

Another 36% of parents report that a grandparent agreed to the change, but did not follow through while 17% say grandparents outright refused their request.

"Whether grandparents cooperated with a request or not was strongly linked to parents' description of disagreements as major or minor," Clark says. "The bigger the conflict, the less likely grandparents seemed to budge."

And when grandparents refused such requests, parents were more likely to put limits on the amount of time their child spent with them, according to the poll.

"Parents and grandparents may not always see eye to eye on parenting but if conflicts aren't resolved, no one wins," Clark says. "Parents who had major disagreements with grandparents were also likely to feel that the conflicts had a negative impact on the relationship between the child and the grandparent.

"Our findings indicate that grandparents should strive to understand and comply with parent requests to be more consistent with parenting choices - not only to support parents in the difficult job of raising children, but to avoid escalating the conflict to the point that they risk losing special time with grandchildren."