Embryo quality assessment with morphological evaluation remains the first-line method of assessment to select the best embryo for transfer. We aimed to determine if an effect of poor quality embryos on good quality ones exists, whether by a paracrine effect or an adverse endometrial influence, when they are transferred together.

We included 412 couples, who underwent intracytoplasmic sperm injection (ICSI) cycles in a tertiary IVF center. Single embryo transfer with a good quality embryo and double embryo transfers with a good + poor quality embryo were evaluated. Overall pregnancy (PR) and live birth rates (LBR) were our main outcome measures.

When PR and LBR are compared, there was no statistical significance between single embryo transfer (SET) and double embryo transfer (DET) groups (51.7 % vs 53.7 %, p = 0.620 and 47 % vs 43.1 %, p = 0.117). When the PR and LBRs were compared between SET from poor cohort and DET group, the outcomes were better in DET group (22.1 % vs 53.7 %, p < 0.001 and 22.1 % vs 43.1 %, p < 0.001). The PR and LBRs of SET from good cohort were significantly better than those of DET (64.4 % vs 53.7 %, p < 0.001 and 57.7 % vs 43.1, p < 0.001). When the PR and LBRs of SET from good cohort and SET from poor cohort were compared, better results were obtained in SET from good cohort.

The addition of poor quality embryo even is of benefit to the LBR, in the setting of when there is only one good quality blastocyst available for the transfer.