I was researching my 2 x g.g.aunt Mary (as you do when you've nothing else to do). She was on the 1841 census with her parents, then married in 1843. I couldn't find her in 1851, her married name was Pape, so I looked at all the similar names, Pope, Pipe, etc. but nothing, I looked on GRO Indexes to see if she'd had any children to give me an idea where she might be, nothing. I looked for her death, nothing. After a couple of hours it occured to me that perhaps her husband had died - he had in 1845, 2 years after their marriage. So I looked for a 2nd marriage and found one in 1848.
Next I found Mary with new husband and a child on the 1851 census, so I looked for her on the 1861 census, nothing. Found a 2nd child on GRO Indexes then nothing, couldn't find the 2 children (the eldest might have been in a boarding school in 1861 - initials only), so I did as before looked for her death etc. etc. Why did I not get the answer straight away - you've guessed it, husband number 2 had died in 1852
so I found another marriage for her, in 1854.
So then I looked for her on the 1861 census, nothing, I thought "Oh no, she's not lost another husband!" she hadn't, this time it was poor Mary that had died aged only 35 in 1857, buried 10 October, not only that her 2nd child also died in 1857 buried in April. What a life, lost 2 out of 3 husbands and 1 child and then died herself.
I'll have to get their death certs now (PDF via GRO) to find the causes of their deaths.
Mary's family didn't have much luck, her eldest sister, my 2 x g.grandmother, died after childbirth aged 28, and the baby died also, her next sister's husband died after only 7 years of marriage, 3 children 2 of whom died and then that sister then had to look after her father for 23 years before she could marry again in 1879, then she died herself in 1891.
Many of the deaths I found in the mid to late 1800s were from diseases that cause no problems nowadays, we don't know how lucky we are.