If the fetus is to become a channel, and particularly a Farris, then the draw is greater and a junct Sime mother would Need more frequent Kills than if the fetus were to become a Gen or a renSime. A non-junct Sime mother would require more frequent transfer.
If the mother is a Gen and the fetus will be a channel, then prior to - 533 Unity, it was probable the child and the mother would not survive the birth. After Rimon Farris discovered and disseminated the techniques for supporting the birth of channels, survival rates changed.
The existence of the channel's exaggerated pre-natal selyn draw is the first clue to the mystery of how to tell Sime from Gen before birth -- and that there is a difference at conception. Given this clue, in the year 232 Unity, Laneff Farris ambrov Sat'htine discovers how to tell Sime from Gen before birth. RenSime
(Source: Index card file. "Prenatal Selyn Draw" --- Attributed to Jean Lorrah -- February 22, 1977) Ancients draw prenatally --- see mysterious miscarriages. Infant begins selyn production at birth. Gen's prenatal selyn draw much, much less than a sime's. Most Gen women can easily supply selyn for the fetus.
In Ancients, and probably in Gens, mother's prenatal selyn production rate increases a FLASH just before birth.
March 19, 1977 --- If FLASH is triggered by a genetic code at a certain state of fetal development, then all sime children born prematurely would die --- would live until they try to draw the FLASH and die of Attrition.
(Source: Index card file. --- "Prenatal selyn drain" --- House of Zeor) It is the reason for Yenava's death. Grandfather: "She'll die if you're not here to supply that baby with selyn when Yenava's delivered."
Klyd: "Yenava is a well trained Companion. I don't expect much trouble." But she would still need him, and this is an obligation
Yenava went into labor and had "complications." Grandfather tried to help her, and failed. All three --- Yenava, Grandfather, and son, dying.