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Changes in DNA methylation during pregnancy and after delivery


 Background

Gestational adaptation takes place soon after fertilization and continues throughout pregnancy, while women return to a pre-pregnancy state after delivery and lactation. However, little is known about the role of DNA methylation in the fine tuning of maternal physiology. In this study, we investigated whether and how the DNA methylation pattern changes in the three trimesters and after delivery in ten uncomplicated pregnancies.
Results

DNA methylation was measured using Human MethylationEPIC BeadChip. There are 14,018 CpG sites with statistically significant changes in DNA methylation over the four time periods (p < .001). Overall, DNA methylation of the non-pregnant state was higher than that of the three trimesters (p < .001), with the protein ubiquitination pathway the top canonical pathway involved. We classified these CpG sites into nine groups according to the changes in the three trimesters. During pregnancy, most CpG sites (61.63%) had subtle or no changes in DNA methylation (Group 9). There were 3,173 (22.64%) CpG sites in Group 7 and 995 (7.1%) CpG sites in Group 8, which were the two groups with DNA methylation changes between the first and second trimesters. The top systems involved in these two groups were associated with embryonic development and organ morphological changes, as shown by the IPA analysis.
Conclusion

The DNA methylation pattern changes between trimesters, which may be involved in maternal adaptation to pregnancy. Meanwhile, the DNA methylation patterns during pregnancy and in the postpartum period were different, implying that puerperium repair may also act through DNA methylation mechanisms.