Before you can understand GERD you need to comprehend what GER is.
GER is describes a continuous every day normal function. Very simply, gastro esophageal reflux (GER) describes the physiologic condition in which stomach contents come back up from the stomach into the esophagus. It is a physiologic process, which means it is normal. In fact all babies have reflux and so do you. It is normal for the stomach to occasionally push its contents up into the esophagus briefly every now and then. It is how often that the stomach does this that makes it a painful thing.
In a healthy baby GER doesn't cause problems. The acid that makes up the refluxed material can irritate the esophagus and upper airway so much that symptoms develop.
When symptoms interfere with a baby's day-to- day activity reflux is referred to s gastroesoophageal reflux disease (GERD). Doctors may refer to it as pathologic reflux.
The difference between GER and GERD is key. It helps us discriminate between a normal function and an abnormal one. Babies with GER spit up but don't suffer any consequences. This is your average happy, healthy growing baby with wet burps.
On the other hand babies with GERD typically face problems relating to feeding, growth or breathing as a consequence of their reflux. These are typically identified, as sick babies ho need medical attention. So while all babies have some degree of GER fewer suffer from GERD.
Everyone including you and your baby experiences reflux during the day. However as an adult you do not need a burping cloth.
Babies' reflux is due to elements of infant physiology and anatomy, which may lead some credence to Dr. Harvey Karp's theory that there is a 'fourth trimester' that a baby experiences outside the womb. (Karp is a very famous contemporary pediatrician whose advice is dutifully followed by many parents.)
The theory is that usually a faulty stomach valve causes GERD. It is faulty in a baby because it has yet to develop.
This valve in question is at the bottom of the esophagus. It is a ring of muscles called the lower esophageal sphincter (LES) that helps keep stomach contents where they belong.
In babies the LES does not stay squeezed closed. When this happens stomach contents are allowed to flow back into the esophagus. By the time a baby is six weeks old these muscles grow stronger and less regurgitation is likely.
The fact that reflux can go on more than one or two months o face tells us that reflux is due to more than just a LES issue.
On of the major factors contributing to reflux in infants is the delayed emptying of the stomach. Under normal circumstance a liquid meal should be gone from a baby's stomaching approximately a half an hour to an hour. During the first months of a baby's life the stomach can be inefficient at emptying and milk has a tendency to sit in the stomach longer than it should. This is because the baby just has slower intestinal motility and there is nothing anyone can really do about it except cope with it and be tolerant until the baby's digestive system is more mature.