[Changes in Gut Microbiome Profile in Pregnant Women with Hyperemesis Gravidarum: A Comparative Study Based on 16S...

Hyperemesis gravidarum (HEG) is a pregnancy complication characterized by severe nausea, vomiting more than four times a day and dehydration, especially occurring in the first trimester of pregnancy. In recent years it has been shown that the intestinal bacterial microbiome profile may be associated with a wide range of diseases. The aim of this study was to determine whether the intestinal bacterial microbiome profiles differ between pregnant women diagnosed with hyperemesis gravidarum (HEG) and those with healthy pregnancies. Fresh stool samples were collected from 15 pregnant women diagnosed with HEG and 14 healthy pregnant women who did not have any complaints in the first trimester. After DNA isolation from the samples, 16S rRNA gene-based microbial profiling was performed with next-generation sequencing. The 16S rRNA V3-V4 region was sequenced with paired-end reads (2×250 base pair) on the Illumina MiSeq platform. The average sequence number for each sample was similar (HEG= ~2.54 million, control= ~1.48 million; p> 0.05). After quality filtering, reads obtained from all samples were analyzed by rarefaction at equal depth. Alpha diversity measures were found to be significantly higher in the HEG group compared to the control group (Shannon, ACE, and Chao1 indices; p< 0.05 for all). In the beta diversity analysis, it was observed that the gut microbiome compositions of the two groups were separated; In the Principal Coordinates Analysis plot, the groups were clearly clustered and the group difference was found to be statistically significant by PERMANOVA test (p< 0.01). Significant differences were also found in the comparisons at the taxonomic level. At the class level, the relative abundance of Clostridia was significantly higher in the HEG group (p< 0.05), while the class Bacilli was dominant in the control group (p< 0.05). At the family level, the abundances of Lachnospiraceae and Prevotellaceae were found to be significantly higher in the HEG group than in the control group (p< 0.05). In contrast, at the family level, the rates of Enterobacteriaceae and at the genus level, the rates of Escherichia-Shigella were found to be significantly higher in the control group (p< 0.05). Some bacterial taxa detected only in the HEG group samples were also noteworthy: Collinsella, Blautia, and Dialister genera, which are only found in the intestines of patients with HEG, were not detected in the control group. In conclusion, these findings reveal that there are significant differences between the intestinal microbiome profiles of pregnant women with HEG and healthy pregnant women. The high microbial diversity observed in the HEG group and changes in certain bacterial groups suggest that processes related to lipid and carbohydrate metabolism may play a role in the pathogenesis of HEG. In the future, the clinical significance and possible therapeutic targets of these differences can be evaluated with more comprehensive studies aiming at clarifying causality.