Maternity clothes and fecundity

Perhaps this isn’t true for every community in America, but the trend in the San Francisco Bay Area when it comes to maternity clothes is for the expectant mother to wear clothes that fit her like a second skin.  With some women, you can practically see the stretch marks:

This is a far cry from maternity clothes in most of the 20th century, when women opted for a full style that indicated pregnancy, without showing the details:

Here’s a question for you:

Why is it that, during an exceptionally fecund time in American history, women wore maternity clothes that played down their pregnancies, while in an era when pregnancy is viewed as a self-indulgent way to destroy Mother Gaia, women flaunt their pregnant bodies?