Luteal phase support
60mg of intramuscular progesterone (Progesterone injection; Xianju, Zhejiang, China), 20-30mg oral progesterone (Dydrogesterone; Abbott Biologicals B.V., The Netherlands) daily were given from the day of embryo transfer (ET) in both NC and AC groups. All women were followed up and pregnancy test with biochemical hCG was performed 14 days after ET. If serum hCG >50 IU/L, luteal support continued. Transvaginal ultrasound was performed 5 weeks after embryo transfer to determine the number of gestational sacs and fetal viability.