A woman with placenta previa is being counselled. The nurse explains that one specific type is considered very dangerous because the anteroposterior (AP) diameter becomes shortened, making fetal engagement difficult and increasing risk of cord compression. Which type is this?

Match Column - I with Column - II and select the correct code: Column - I (a) Complete Parthenogenesis (b) Arrhenotoky (c) Thelytoky (d) Incomplete Parthenogenesis Column - II (i) Haploid male parthenotes (ii) Exclusively female; males rare/absent (iii) Cyclic parthenogenesis (iv) Diploid female parthenotes

Teratogens primarily exert their most disruptive effects on the developing embryo during which period?