Introduction
Late miscarriage, also known as second-trimester or mid-trimester
pregnancy loss, has different definitions across
countries(1, 2). In China, LM refers to a complete
pregnancy loss between 12 weeks and 28 weeks of gestational age. The
main reasons for LM include cervical incompetence, fetal anomaly,
maternal infection as well as premature rupture of membranes according
to a previous retrospective study(3). LM is a heavy
blow to pregnancy women at the second trimester who are almost preparing
for delivery and
brings
about substantial physical harms (4). There is no
doubt that LM is more devastating for infertile women who have spent
plenty of time and money on in vitro fertilization (IVF)/
intracytoplasmic sperm injection (ICSI) treatments.
The pregnancy loss rate among IVF population is reported to be
approximately 15% (2, 5, 6), which is slightly higher
than that after natural conception (7). The vast
majority of pregnancy loss occurs before 12 weeks of gestational age,
called early miscarriage (EM), and only 1-2% of pregnancies are
spontaneously terminated after 12 weeks (8). It has
already been known that a history of EMs significantly increased the
risk of recurrent pregnancy loss and has an adverse influence on live
birth (9, 10). Thus, the focus has always been on EM
by clinicians in IVF cycles and the impact of LM is greatly
underestimated(2, 5, 11).
It’s documented in a retrospective cohort study that women with a
history of previous LM or stillbirth had a high recurrence risk during
the subsequent pregnancy in general population(12).
Further, both two studies have found that there was a significant
association between a previous LM and subsequent adverse pregnancy
outcomes, including an elevated EM rate and a reduced live-birth rate,
after conventional IVF (13) or preimplantation genetic
testing for aneuploidy (14). However, some studies
drew a contradictory conclusion that one LM did not
correlate
with pregnancy prognosis (15). More importantly, they
all failed to further investigate the separate impact of LM with
different causes on subsequent pregnancy outcomes.
Therefore,
it
remains unclear whether and how previous LM might impact future
outcomes.
In the present study, the main objective was to explore whether a
previous LM after first embryo transfer has a prognostic impact on the
subsequent pregnancy outcomes during IVF.