There seems to have been a tendency for women ---even noblewomen-- to have about one pregnancy every 18 months: look at all the kids Ed III & Philippa had. The birth rate was apparently rather astonishing, perhaps 35%, right up there with the rest of the Third World. However, the infant mortality rate was also Third World.

Life expectancy was pretty abysmal. The figures which follow are based on statistics for landholding families in England. The source had figures for various periods from 1200 through 1450, but those for 1276-1300 have been used because the effects of Plague are minimized.

Age                           Prospects                     Total                         

 0                            31.3  126                     31.3                          

10                            32.2  129                     42.2                          

20                            25.2  101                     45.2                          

30                            21.8   88                     51.8                          

40                            16.6   65                     56.6                          

60                             8.3   34                     68.3                          

80                            3.8   16                      83.8
                          

For women the picture was a little different. They managed to survive their first 10 years about 10% better than men. Then they began to fall seriously behind as they reached childbearing age. Women 14-40 had a life expectancy only about 50% that of males in the same group: having babies was more dangerous than going to war. However, after 40 female life expectancy ran about 10% better than male. At a guess, a woman who was never pregnant probably maintained that 10% edge throughout her life. One possible reason for becoming a nun.

Age                           Deaths/1000                   %                             

0-4                           325                           32.5                          

5-9                           239                           23.9                          

10-14                         104                           10.4                          

15-19                         71                            7.1                           

20-24                         9                             0.9
                           

This data is for unmarried women whose fathers had registered them with an endowment fund: they would deposit a sum of money at birth and it would pay off in a dowry at the time of marriage depending on how long the money had been in the Fund. As such, it reflects the life expectancy of fairly well-off folks. It was almost certainly worse for the lower classes.

People born 1200-1275 had apparently better chances than those born later. This could be due to poor records.

Marital Age Patterns. Apparently women got married off pretty early, being considered eligible at 14, but their husbands usually ran more than 10 years older. Among nobles, and especially royalty there was less predictability, so you get frequent infant marriages --or at least betrothals-- and occasional unmarried noblewomen in their early 20s. These last may have had something to do with their prospects: a female heir might be able to stave off marriage in hopes of getting a really good catch, like the king. Generally the older a noble spinster was, the younger her eventual husband was likely to be. And forget about looks, with the aristocrats is was genealogy and money that counted most. This led to the general acceptance of mistresses for the men, although wives faced severe sanctions if their extramarital activities were found out.