Interpretation
We have provided a new insight that adenomyosis can trigger abdominal
pain during pregnancy. Fibroids cause abdominal pain in up to 28% of
cases during pregnancy,(12) but whether the same physiologic changes
occur in adenomyosis during pregnancy is not well understood. The
pathophysiology underlying pain mechanism in fibroids is degeneration,
which occurs predominantly during the second and early third
trimesters.(18),(19) It is generally diagnosed by
confirming the presence of pain directly over the fibroid correlating
with ultrasound examination findings, and further accurate diagnosis can
be made with MRI.(20, 21) The degeneration of fibroids is often
accompanied by enhanced inflammation and an increase in CRP
levels,(12),(13) which decrease with the amelioration
of pain, usually within two weeks.(12),(20) However,
whether this phenomenon is linked to adverse perinatal outcomes has not
been conclusive.(22) Considering the similarity between fibroids and
adenomyosis, the timing of pain onset that we reported in this study and
the past reports of degeneration of adenomyosis during pregnancy
indicate that the pain followed by the enhanced inflammatory response
observed in our cohort mimics the degeneration of fibroids.(11, 23, 24)
Nevertheless, it seems unquestionable that some proportion of women with
adenomyosis develop pain during pregnancy.
A recent meta-analysis showed that women with adenomyosis had an
increased likelihood of PE (odds ratio [OR]: 4.35; 95% confidence
interval [CI], 1.07–17.72; p <0.05), although the
pathophysiology underlying this result is unknown.(5) In our study, the
adenomyosis pain onset was associated with the onset of PE, which
intriguingly was more conspicuous in patients with elevated CRP levels.
Interestingly, the median time from the maximum CRP level to the onset
of PE was 15 days, and the CRP level decreased in the days before PE
development. Several mouse models of PE have been reported that were
induced by inflammatory cytokines.(25-28) Although CRP cannot be used as
a marker for predicting the onset of PE, circulating CRP is reported to
be elevated in some groups of women, such as those with periodontal
disease or obesity, before the onset of PE. (29-31) Although the number
of cases is limited, considering that the maximum CRP preceded the onset
of PE in our cohort and that previous reports show an association with
inflammation and the onset of PE, enhanced inflammation at the
utero-placental unit may be the key factor to induce the onset of PE in
women with adenomyosis pain.