Well, I've given birth, and also had a cancer diagnosis, and I can tell you that the last is in no way comparable with the first. Birth is hard and scary and painful, but you are having the joy of a new child, and labour ends after a relatively short time. A cancer diagnosis is hard and scary, and the biopsies alone are painful, let alone the surgery and chemo and rads... and it goes on for months (years, if you take on board the worry about recurrence, which fades but doesn't end) plus you don't have anything but the prospect of early death, leaving small kids in my case had I been unlucky, waking you through the night.
Which is the crux of the point. If having a partner with you during cancer treatment meant you were more likely to survive or live longer, then the argument is comparable. But sadly it simply isn't the case.
Not all pregnancies end with a joyful live birth. Not all births end with a healthy baby. Not all births end with a healthy mother and sadly though rare, some mothers won't survive at all.
Decisions about drugs, treatment, emergency c sections, undetected complications - all whilst you are stuck as an immobile life support vessel to your unborn child.
Then there's the absence of post natal health checks, breastfeeding support, those crucial baby weigh ins for the first few weeks, general access to advice, support and communication - all stopped overnight.
By what percentage will PND have increased this year when retrospective diagnosis catch up next year?
I'll repeat what other pp's have said - it's proven that birth partners improve outcomes for mother and baby. It is nonsensical for this to be ignored.