"My 20-month old granddaughter usually does not nap (my daughter always puts her down after lunch for at least a 1-hr quiet time).  She occasionally had night terrors, usually lasting around 30 minutes.  In the last six months, her night terrors  have become more frequent.  Last week she had them two nights in a row. 

Her pediatrician has not been very helpful, just saying that night terrors don't last that long and she will out-grow them.  We haven't found much information either in books or the internet.

Could you give us any guidance?  Do you do telephone consultations?"

- Gloria

Hi, Gloria.  Thanks for your email.
 
We just don't know much about night terrors in general, but one of the most prominent "causes" of them is insufficient sleep.  You don't mention how much sleep your granddaughter gets in a 24-hour period, but you mention that she doesn't nap.  (The other causes are overstimulation or similar extreme "stress.", even when it's happy "stress.")
 
A 20-month-old that does not nap strikes me as concerning.  It would be unusual for a child this young to have "outgrown" the afternoon nap.  For most children, the afternoon nap continues until age 4 or 5 or even 6 years of age.
 
When a 20-month-old is routinely not getting an afternoon nap, it is very likely she is not getting enough sleep, and this situation alone can predispose the child to the occurrence of night terrors. 
 
The lack of nap plus the night terrors tells me it's likely your granddaughter is not getting enough sleep each day and night.
 
I can't tell whether or not you're aware of my book, or whether you've read it, but it is very easy for parents and caregivers to miss the good opportunities for sleep in their little ones.  My book describes a very simple formula you can follow to make sure your granddaughter gets her naps.
 
My book also briefly describes that although the brain of an adult can compensate for or make up for lost sleep, this neurobiological process is not yet present in early life.  This buildup of what the sleep researchers call "sleep pressure" in a child who's had insufficient sleep time to discharge it, leads to a build up during deep slow wave sleep in those first few hours of nighttime sleep, to a kind of a super intense, super deep sleep.  The problem is a child's brain can't process this super deep sleep like an adult's brain can, so it can lead to events like night terrors, and is one of the reasons night terrors are so common in the young, but much rarer in adults.
 
By the way, your pediatrician is correct that your granddaughter will outgrow the night terrors.  The problem is, we don't know exactly when and it could be literally years from now. 
 
To my mind, there IS something you can do to help them become less frequent in the meantime. 
 
I would urge you to help your granddaughter get all the sleep she needs, including ensuring an afternoon nap.  I strongly suspect that when you are successful with this, the night terrors will become much less frequent, and they may in fact disappear altogether.  Even if they don't disappear completely, it's worthwhile to help her get more sleep for these simple reasons:  a) it will not cost you anything, and b) you will not harm your granddaughter at all by doing so.  In fact, by helping her get more sleep you may be benefitting her health in many ways for years to come.
 
Let me know how it goes, if you're so inclined.  
 
Polly.