A 2002 study of pregnant woman showed a significant correlation between women who had symptomatic morning sickness, and/or a diagnosis of Hyperemesis Gravidarum, had an aggravated Helicobacter pylori infection. Also Known as H. pylori, this infection is a bacteria that lives in your lower gut and is aggravated by pregnancy hormones. Those hormones including HCG tend to level out after 12 weeks, which is why most morning sickness goes away around the end of the first trimester.
However, when the H. Pylori infection is severe enough it can persist causing telltale nausea and vomiting for your entire pregnancy.
Does that mean there is a cure for morning sickness!? It is possible to cure an the H. Pylori infection at least. It’s difficult to do during pregnancy since the antibiotics that are needed have not been sufficiently tested for safety in pregnancy. However, if the infection is severe enough the risks might outweigh the benefits.
There is some good news! You can get treated when you are no longer pregnant, and the study shows it’s likely that you won’t have morning sickness during your next pregnancy. If you have been diagnosed with HG, talk to your care provider about getting tested for H. Pylori. The accepted treatment is 2 weeks of antibiotics. I also recommend taking a high quality probiotic to help balance out your gut flora. Antibiotics can cause yeast infections and other digestive issues which can be unpleasant.
You can find the full study Here: https://www.ncbi.nlm.nih.gov/pubmed/12445985