Interpretation
Abortion is a common complication of pregnancy. The aetiology of
abortion is complex: obesity17, insulin
resistance18, hyperandrogenism19,
the quality of oocytes and endometrial abnormalities might be associated
with the occurrence of abortion 20-22. As reported in
prior studies, women with PCOS are associated with an increased risk of
abortion23,24. In addition, Wang et
al.25 found that the incidence of abortion was
increased in women who underwent ART, with a possible mechanism related
to corpus luteum insufficiency.
In our study, the incidence of abortion was significantly increased in
PCOS phenotypes A and D, and with the coexistence of OA and PCOM in PCOS
phenotypes A and D. We speculate that the combination of OA and PCOM
might increase the risk of abortion by affecting oocyte quality. A study
by Barnes and colleagues reported that oocyte maturation and the
fertility rate of anovulatory women were significantly lower than those
of regular cycling women; their embryo development ratio followed a
similar trend26. Another study of anovulation in cows
found that anovulation also leads to major shifts in gene expression in
elongated conceptuses during preimplantation stages; transcripts
involved with the control of energy metabolism and DNA repair were
downregulated, whereas genes linked to apoptosis and autophagy were
upregulated27. Furthermore, a recent study revealed
decreased oocyte quality in PCOM due to the abnormal activation of
one-carbon metabolism and hypermethylation of mitochondrial
DNA28. These results support the above conjecture.
Moreover, we also observed that the rate for the presence of
a
corpus luteum (because of different
endometrial preparation protocols for FET) in PCOS phenotypes A and D
was significantly lower than that in controls, which might be another
reason for the higher rate of abortion. In clinical practice, for PCOS
women with OA, clinicians generally adopt a hormone replacement therapy
(HRT) cycle to prepared the
endometrium for FET29. Recently, Xu et
al.30 noticed that HRT cycles were related to a higher
abortion rate, which is consistent with the results of a prior
study31. The corpus luteum is an important source of
hormones in pregnant women12,32, but during
endometrial preparation, a corpus luteum is absent in a HRT cycle.
Additionally, administering
exogenous hormone in a HRT cycle might increase the risk of
thromboembolic events and could damage placentation, which may then lead
to abortion33,34.
It is generally known that obesity has an undesirable impact on women’s
reproduction35. Obesity increases the rate of
abortion36 and is an independent risk factor for
abortion37,38. Obesity affects follicle development by
affecting sex hormone secretion and metabolism35;
other studies have found adverse effects of obesity on the quality of
the embryo 39 and endometrial
receptivity40. In the present study, the BMI in PCOS
phenotype A and D groups was significantly higher than that in the
control group. Before the initiation of FET, obese women can reduce
their weight to optimise pregnancy outcomes41.
Interestingly, we also noticed that the age of the women in PCOS
phenotypes A and D was lower than that of women in the control group.
It is well documented that maternal
age increases the incidence of abortion42,43. It is
possible that other factors masked the effect of age on abortion. The
average age of patients was 30.62 ± 4.07 years in our study, which may
have a relatively small impact on abortion. Previous studies found that
an advanced age increased the risk of abortion, usually over the age of
35 or 3844,45. In addition, previous studies have
suggested that HA is associated with increased rates of
abortion46. However, this was not found in our study.
A recent systematic review and meta-analysis also showed that HA does
not increase the risk of abortion in patients with
PCOS18.
Therefore, for women with PCOS phenotypes A and D, lifestyle
interventions such as improved diet and increased exercise were used to
reduce body weight before FET; natural or ovulation-induced cycles are
recommended as a priority for endometrial preparation in FET, and an
appropriately increased luteum phase supported. Additionally, pregnancy
follow-up after obtaining a clinical pregnancy should be strengthened,
and, with any sign of an abortion, treatment should be promptly
provided.