Blue and Black Cohosh in Pregnancy and Labour

What is the difference between Blue Cohash & Black Cohosh? Are they safe to take during pregnancy? Do they help in aiding contractions or labor?

Blue and Black Cohosh are both used in labour and childbirth, but not usually taken during the rest of pregnancy. Individually and together, they may cause premature uterine contractions resulting in miscarriage. Blue Cohosh is used to increase blood flow to the uterus. Black Cohosh has an estrogenic effect and is used to balance female hormones. They are sometimes used together to stimulate uterine contractions when a birth is overdue or the birthing process slow, and the mother or child may be in danger. They are also used together to ease menstrual pain.
Other properties and uses:
Black Cohosh is a nervine and muscle relaxant, used in pain and muscle spasm. Its anti-inflammatory properties make it useful in rheumatoid arthritis.
Blue Cohosh is antispasmodic, relieving pains and cramping.