That book (Deathwatch by Steve Parker) isn't accurate to the rest of genestealer fluff. It has women being forcibly restrained and then implanted with eggs that then gestate unnaturally within them, almost like the facehuggers from Alien.
In the actual fluff on genestealers, humans being captured, infected with 'stealer DNA and mind-raped into obedience and loyalty to the cult by the Patriarch, then knocked up by either hybrids or other brainwashed/infected humans, not implanted with eggs. They then carry the child to term as in a normal pregnancy and their brainwashing means that whatever unspeakable alien horror they eventually birth, they'll think it is the most beautiful baby they've ever seen and dote over it like a beloved child.
Honestly I think that is more horrific than Parker's alien rip-off version although his version is more my fetish, especially the female Inquisitor who gets captured and found by the kill team chained to an altar with a massively swollen belly