Briefly explain $\rm {IVF}$ and $\rm {ET}$, What are the conditions in which these methods are advised ?

    In vitro fertilisation ( $IVF-$ fertilisation outside the body in almost similar conditions as that in the body) followed by embryo transfer $(ET$) is one of such methods.

In this method, popularly known as test tube baby programme, ova from the wife/donor (female) and sperms from the husband/donor (male) are collected and are induced to form zygote under simulated conditions in the laboratory.

The zygote or early embryos (with upto $8$ blastomeres) could then be transferred into the fallopian tube ($ZIFT -$ zygote intra fallopian transfer) and embryos with more than $8$ blastomeres, into the uterus ($IUT -$ intra uterine transfer), to complete its further development. Embryos formed by in-vivo fertilisation (fusion of gametes within the female) also could be used for such transfer to assist those females who cannot conceive.