13 month old throwing up at night only?

It could be the position in which he is laying. The flatness could cause him to spit up.

Does he nap in his cot during the day? If so, for how long?

It may be a good idea for you to raise the head of his crib slightly, by putting a rolled towel UNDER the mattress at the head end to raise it. This will allow his airways to open and for his food to stay in his stomach.

This is often what mothers with reflux babies do to stop spit up.

Throwing Up At Night Only

My first thought was acid reflux, as well. Does he happen to be eating shortly before bed? If so, while he's laying down, all that acid from his food will just sit on his tummy, causing him to spit up or vomit. If it does happen to be reflux, it's helpful keep him sitting up for an hour after eating (even if he's sleeping), and to have one end of the crib slightly elevated. Reflux can be pretty uncomfortable for the little ones, and even if it's not that, it doesn't sound like he's too comfy at night in general, so I would still call in to your doctor and see what they recommend. But it doesn't sound like anything to be panicked over, just usual mommy stuff ;) Good luck, and I hope this helps! :)

I'm a medical researcher. It is widely agreed among physicians and medical paraprofessionals, that initial diagnosis, mostly by using a typical acid reflux symptoms questionnaire, is necessary to ensure the most effective and quick treatment for this condition. Approx 70% of the acid reflux diagnostics that are based on the presence of typical symptoms are accurate. Since acid reflux, also called GERD (gastroesophageal reflux disease), can cause patients a great deal of discomfort and result in severe complications, it is highly important to know how to identify its symptoms in order to quickly diagnose and treat it.

If you know you have acid reflux you can try this natural program http://www.goobypls.com/r/rd.asp?gid=568

elevate the head of his crib. it might help. some kids don't have a strong stomach, so they will throw up when lying down. if it doesn't help, go to the doctor.