Nausea and vomiting during pregnancy is very common. Many women who are pregnant experience some symptoms of nausea or vomiting and about a third experience moderate to severe symptoms. The impact of symptoms is wide-ranging and can be substantial, including weight loss, disrupted routines, and impeded ability to work and/or care for children. Severe cases may result in hospitalisation. Women with severe symptoms also have a higher incidence of anxiety and depression. It is unclear if anxiety precedes symptoms of nausea and vomiting or is a consequence. Anxiety and severity of nausea and vomiting are both moderately heritable. We tested if a genetic predisposition to anxiety was associated with more severe nausea and vomiting during pregnancy. As a comparison, we also tested if a predisposition to depression was associated with more severe nausea and vomiting during pregnancy.
Participants were 1440 parous women reporting on the severity of nausea and vomiting experienced during their most affected pregnancy. Severity of nausea and vomiting was measured on a 5-point scale, from “None” to “It really disrupted my daily routine. I lost weight. I was prescribed medication or put on a drip/feeding tube.” Genetic predisposition for anxiety and depression was measured with polygenic risk scores (PRS). For anxiety the PRS loadings were from the summary statistics of a GWAS on anxiety, conducted on 37,215 cases and 120,151 controls from the UK Biobank. For depression the PRS loadings were from the summary statistics of the second depression GWAS from the Psychiatric Genetics Consortium, conducted on 135,458 cases and 344,901 controls.
A genetic predisposition to depression did predict more severe nausea and vomiting during pregnancy; it explained ~0.5% of the variation in severity of nausea and vomiting during pregnancy. There was a suggestive association of a genetic predisposition to anxiety with severity of nausea and vomiting in pregnancy. However, this did not survive multiple testing, and the PRS lost precision with increasing p-threshold.
This provides support for the hypothesis that genetic factors that predispose a person to depression also contribute to the severity of nausea and vomiting experienced during pregnancy. The GWAS used for the loadings in the calculation of the anxiety PRS was much smaller in size than that of depression. It may be that with a larger, more powerful anxiety GWAS the precision of the anxiety PRS will improve the PRS for anxiety and lead to more stable results for anxiety.
