GMAT Critical Reasoning (CR) | Aggressive fertility treatments are not responsible for the

Aggressive fertility treatments are not responsible for the rise in the incidence of twin births. Rather, this increase can be attributed to the fact that women are waiting longer to become mothers. Statistically,women over 35 are more likely to conceive twins, and these women comprise a greater percentage of women giving birth than ever before.

Theargument above is flawed in that it ignores the possibility that

many women over 35 who give birth to twins are not first-time mothers
women