What are the chances for twins without family history?

2%: In us, of the total # of pregnancies, twin pregnancy account for 2 % of pregnancies in total.

2-3%: Roughly 2-3% chance of twins for all comers. It also depends on the age of the woman at the time she conceives. There are also differences due to race. Interstingly, chance for identical twins is ~0.5% regardless of race.

Depends on race: African-american women have higher twin rates. Also, more obese women and those consuming multivitamins before they get pregnant are at higher risk for twins. Of course, by far the greatest predictor of twins is ivf (assisted reproduction).

Twin risk: I agree with other answers. Let me add that women older than 35 also have an increased risk because they have a higher natural level of FSH ( follicle stimulating hormone). In addition to ivf, any fertility medication increases the risks but to a variable degree. We have a ways to go but the trend to more single embryo transfer, is reducing the multiple rates from ivf. Best wishes.