Twin parenthood, but not ART, has a negative impact on the mental health of mothers and fathers during the transition to parenthood. ART parents' mental health was not affected by parity or children's health-related factors.

A single HCG reading on day 12 after embryo transfer helps to plan the subsequent follow-up. Male factor infertility and ICSI are associated with relatively low HCG values in viable pregnancies.

Our results indicate that subject- and infertility-related mechanisms other than the number of transferred embryos influence the neonatal outcome of singleton IVF pregnancies.

II-2.

Successful ART did not predict mental health problems during the transition to parenthood. Moreover, ART couples' mental health was remarkably resistant to social and child-related stress during the transition to parenthood.