Observational parameters and outcome variables
Baseline parameters included age, BMI, duration of infertility, primary
infertility, antral follicle count (AFC), basal follicle stimulating
hormone (FSH), anti-Müllerian hormone (AMH), the mean diameter of
initial uterus, history of dysmenorrhea and IVF-related parameters. The
mean diameter of uterus was calculated as the average of long and wide
diameter in longitudinal section measured by TVS on day 2-6 of the
menstrual cycle. According to the verbal multidimensional scoring
system(14), dysmenorrhea was classified into none,
mild, moderate and severe. The primary pregnancy outcome was CPR, and
the secondary pregnancy outcomes included implantation rate (IR),
biochemical pregnancy rate (BPR), ectopic pregnancy rate (EPR),
miscarriage rate (MR), early MR, late MR and LBR.
Serum β-hCG
level was examined 14 days after ET.
Biochemical pregnancy loss was defined as elevated serum β-hCG level in
the absence of invisible intra-uterine and extra-uterine gestational
sac. Clinical pregnancy was defined as the presence of
intra-uterine pregnancy. Ectopic
pregnancy was defined as the
presence of gestational sac or mass outside uterine cavity.
Miscarriage was defined as pregnancy
loss before 28 gestational weeks. Clinical pregnancy loss ≤12
gestational weeks was early miscarriage, vice versa, pregnancy loss >12
gestational weeks was late miscarriage. IR was defined as the ratio of
total numbers of gestational sac confirmed by TVS to total numbers of
transferred embryos.