"Maternal morbidity" refers to health problems that women may experience during pregnancy, childbirth, or shortly after giving birth. It includes complications and illnesses that can affect the mother's physical or mental health. Full definition
The last link addressed the issue best, I thought: «The increase in risk of severe maternal morbidities in non-white women seems to be independent of differences in age, socioeconomic and smoking status, body mass index, and parity between ethnic groups.» (skepticalob.com)
For parous women the rate of severe acute maternal morbidity for planned home versus planned hospital birth was 1.0 versus 2.3 per 1000 births (0.43, 0.29 to 0.63 and 58.3 %, 33.2 % to 87.5 %), the rate of postpartum haemorrhage was 19.6 versus 37.6 (0.50, 0.46 to 0.55 and 47.9 %, 41.2 % to 54.7 %), and the rate of manual removal of placenta was 8.5 versus 19.6 (0.41, 0.36 to 0.47 and 56.9 %, 47.9 % to 66.3 %). (skepticalob.com)
The image below compares the incidence of severe maternal morbidity in two groups. (skepticalob.com)