Study procedures
Eligible women were indicated for IVF or ICSI. A long or short protocol
with the use of a gonadotropin-releasing hormone (GnRH) agonist, or a
protocol with a GnRH antagonist, or a mild stimulation protocol was
applied for controlled ovarian stimulation according to women’s age, BMI
and ovarian reserve function. The ovarian stimulation protocols in our
center had been described in detail previously(17).
Follicular growth was monitored by ultrasound and as soon as at least 2
follicles with diameters ≥ 18 mm were detected, an hCG trigger for final
oocyte maturation was given. Then transvaginal ultrasound-guided oocyte
retrieval was performed 34–36 h after hCG administration.
Conventional IVF or ICSI was performed according to the male partner’s
semen quality in laboratory. Good-quality embryos were selected for
transfer at cleavage-stage according to Puissant criteria(18) or at blastocyst stage according to Gardner
criteria (19).
Luteal-phase support was performed on the day of oocyte retrieval or on
the day of endometrial transformation, and continued until 12 weeks of
gestation. Different luteal-phase support regimens were adopted for
embryo transfer in our center, including oral dydrogesterone (20 mg,
twice a day) alone, oral dydrogesterone (20 mg, twice a day) combined
with utrogestan vaginal capsules (200 mg, once a day) or crinone 8%
vaginal gel (90 mg, once a day).
Biochemical pregnancy was determined when a serum human chorionic
gonadotropin (hCG) level reached 25 mU per milliliter at 14 days after
embryo transfer (ET). Clinical pregnancy was confirmed when a
gestational sac by transvaginal ultrasound was observed at 3-4 weeks
after a positive hCG test. Biochemical pregnancy loss was defined as
spontaneous pregnancy demise based on a previous positive pregnancy test
that then becomes negative with no gestational sac observed through an
ultrasound evaluation. EM was defined as a termination of pregnancy
before 12 weeks of gestational age in this study. The preterm birth was
defined as a successful delivery before
37
gestational weeks and live birth was defined as the birth of at least
one living baby after 37 weeks of gestation.