A common picture of the Middle Ages is a huge family. In Game of Thrones you see some noble houses where women have five children or more. I have heard some comments from people in conversation that the maternal mortality rate, defined as
"The death of a woman while pregnant or within 42 days of termination of pregnancy, irrespective of the duration and the site of the pregnancy, from any cause related to or aggravated by the pregnancy or its management, but not from accidental or incidental causes." was much higher than it is now to the point that child birth was very dangerous. I heard some numbers thrown around from 10 to 40 percent which seems a little high.
I know this will vary wildly for location and time but how would it compare for a noble family compared to a poor family? How much did the health care matter? Is it realistic to have a family of more than 5 people or did a wife usually expect to die from that?
The Middle Ages is a bit of a broad area to be asking about, both geographically and chronologically, but I can speak to one specific example when it comes to nobility, and generally when it comes to the population as a whole.
In the period after the First Crusade, a large number of separate crusader states were set up (ruled by Western Europeans), and a recurring issue that occurred was that these rulers would die without a surviving male heir, which was a combination of the high maternal and infant mortality rates of the period, and the violent lives that many of them led. Of course, one can find counterexamples- William the Conqueror and his wife Matilda had nine children, all of whom lived into adulthood, so it certainly wasn't black and white.
Regarding the common people, hard statistics are few and far between- in the abstract, one source that I've used indicates that there were periods lasting for centuries where population growth was flat or negative, indicating that the number of children surviving to bear the next generation was below the replacement level. That changed in the High Middle Ages, when populations grew quite a bit for a while, but then of course the plague reversed much of those gains.
Sources: The Crusades through Arab Eyes, by Amin Maalouf, and "Population in Europe," by Josiah Russell, through the Internet Medieval Source Book (which is a wonderful resource, btw.) Link to statistics: http://www.fordham.edu/halsall/source/pop-in-eur.asp
Well, numbers in excess of five or even ten definitely weren't uncommon. Someone like Eleanor of Aquitaine (1122-1204) had ten children from two marriages. Owain Glyndŵr (c.1349 - unknown) and his wife Marred had ten children. Elizabeth Woodville (c.1437 - 1492) had twelve. Holy Roman Emperors Henry III (1017 – 1056) and Henry IV (1050 – 1106) each had six children with their respective wives.
Not a representative sample, but a few out of many historical examples of large noble families.