Women in their early thirties are for the first time having more babies than younger moms in the United States, according to new data released by the Centers for Disease Control and Prevention. According to health experts, the shift was caused by more women choosing to wait longer to have children, as well as a steady national drop in teen births. Now, the birth rate for women in the 30-to-34 age group is about 103 per 100,000. For women ages 25 to 29, it’s 102 per 100,000. The average age when women have their first child is 28, and the overall birth rate was down to about 62 births per 100,000 women, ages 15 to 44. Bill Albert, of the National Campaign to Prevent Teen and Unplanned Pregnancy, said teens are now growing up with fewer and fewer peers getting pregnant. “We always talk about peer pressure as a negative, but it can be a force for good,” he said.