Potty training has always been high-stakes territory for parents and, these days, parents can feel like they're getting bombarded with toilet-training advice from all directions, much of it conflicting. So how is a parent supposed to make sense of it all?
Why not check out some of the recent potty training research and then consider how those facts mesh with what you already know about your child.
There's little benefit to starting toilet training before age 27 months. Researchers at the University of Pennsylvania found that, on average, if you start training children at a younger age, the entire process ends up taking longer. This is because parents who get a too-early start may have to wait for their children to become physically and mentally ready for toilet training. (You may be ready for your child to be out of diapers, but that doesn't necessarily mean your child is developmentally ready to master the skills involved in learning how to use the toilet.) The takeaway message? Toilet training will be easier on you and your child if you wait until your child is both physically and emotionally ready to start toilet training.
You may be able to spot and head off some of the early warning signs of toilet training problems. Stool training refusal—a problem which occurs in approximately one in four young children, according to researchers at the University of Pennsylvania—typically begins with hard bowel movements and pain during defecation. If parents can head off or detect these earlier problems, problems with stool training refusal (an understandable desire to avoid future bowel movements because bowel movements are now associated with pain or discomfort) can often be avoided.
Temperament plays a key role in how easy—or how difficult—the toilet training process will be. Researchers at the Harvard Medical School found that children whose parents described the experience of trying to toilet train their child as "difficult" were likely to have temperamental traits that are often categorized as "difficult." Children in the so-called difficult group were likely to hide when it was time to have a bowel movement (74%) and to ask for a pull-up (37%).
Girls tend to be toilet-trained earlier than boys, but there's huge variation from child to child when it comes to acquiring individual skills. Researchers at the Medical College of Wisconsin, Milwaukee found that the median age for "staying dry during the day" was 32.5 months for girls and 35 months for boys, but there was variation of up to a year in the attainment of individual skills (e.g., showing an interest in using the potty, staying dry for two hours, indicating a need to go to the bathroom).
Keeping your child in diapers during the toilet-training process can be counter-productive. Researchers at the University of Nevada discovered that wearing diapers increased the rate of accidents (e.g., wetting the diaper) and decreased successful trips to the potty.
More children with special needs are capable of being toilet trained than previously believed. Researchers in the UK have discovered that the best method of determining whether a particular child is a good candidate for toilet training is to assess bladder and bowel maturation and then break down each of the tasks a child will have to master into a series of smaller tasks: tuning into body signs, controlling muscles, getting to the potty in time, managing clothing, getting on and off the toilet, and hand-washing.                                                 
 

Ann Douglas is the author of numerous books about pregnancy and parenting, including Sleep Solutions for Your Baby, Toddler, and Preschooler; Mealtime Solutions for Your Baby, Toddler, and Preschooler  See www.having-a-baby.com