Outcomes
Only the pregnancy outcomes from
the first FET cycle were recorded in this study, and were followed up
until June 2019. The primary outcome was the ongoing pregnancy rate and
the secondary outcomes included incidence of
premature LH surge (LH ≥10 IU/l),
clinical pregnancy, miscarriage, multiple pregnancy, ectopic pregnancy
and implantation rates. Clinical pregnancy was defined as the presence
of at least one gestational sac on ultrasound at 6 weeks. Ongoing
pregnancy was the presence of at
least one fetus with fetal pulsation on ultrasound beyond 10 weeks.
Fertilization rate was the percentage of zygotes with two visible
pronuclei among inseminated (IVF)
or matured (ICSI) oocytes. Miscarriage rate was defined as the number of
miscarriages before 20 weeks divided by the number of women with
positive pregnancy test. Multiple pregnancy was defined as a pregnancy
with more than one gestational sac detected on ultrasound at 6 weeks.
The implantation rate was calculated as the number of gestational sacs
seen on scanning divided by the number of embryos replaced.