In a very real way, June means weddings. The end of school and great weather motivate young couples to tie the knot and schedule summer weddings.

Back in the old days, summer weddings meant an uptick in births 10 months later. This is less true today. Utah’s fertility rate is at a historic low, and state demographers are asking, “What to expect when no one’s expecting?”

I didn’t come up with that clever turn of phrase. Journalist Jonathan Last wrote a book with that title, which is a twist of the title from a popular book written for expectant mothers. In his book, Last presents evidence about America’s falling fertility. He argues that white, college-educated Americans have put into practice their version of China’s one-child policy. He points out that if it weren’t for immigration, the U.S. population would be shrinking.

Utah is different. We continue to have the highest fertility rate in the nation. Births still outnumber deaths in Utah by approximately 33,000 each year. But things are changing here too, and Utah’s declining fertility rate is one of the most interesting demographic trends to watch.

Utah’s total fertility rate, which is a measure of births per woman, has fallen from 4.3 in 1960 at the tail end of the Baby Boom to 2.3 today. The rate has fallen for eight consecutive years and now stands at a historic low. We are becoming more like the nation. So much so that the old Utah wedding joke may not apply anymore. (For those of you who don’t know the joke it goes like this: “How do you tell a Utah wedding? The bride is NOT pregnant, but the mother of the bride is!”)

Unpacking Utah’s declining fertility rate is a lot like unpacking the nation’s. Advances in birth control (most notably the oral contraceptive pill), increasing female participation in the labor force and rising educational attainment of women are a few of the most obvious explanations. It’s also important to recognize the impact of in-migration on fertility patterns. Migrants often bring different fertility patterns with them.

But, there’s one trend unique to Utah that deserves attention. The mission-age policy change of The Church of Jesus Christ of Latter-day Saints is changing the post-high school trajectory of many Utahns. Since October 2012, young LDS men can serve a mission at age 18 (down from 19), and young LDS women can serve at 19 (down from 21).

While the LDS Church does not publish detailed information on the age and gender of missionaries, the news reports I’ve read suggest there are currently about 70,000 missionaries worldwide and 1 in 4 are female. The same sources estimate the number of female missionaries has nearly tripled since the age change. This is a big deal.

Will these sister missionaries delay marriage? Will they delay childbearing? Will they return from their missions and chose to further their education? Will they pursue a professional career? These choices will have a profound impact on Utah’s future.

My personal feeling is that as young LDS women leave home, become more independent, see new parts of the world, serve in leadership positions, gain confidence and strengthen their sense of self, they will enthusiastically embrace more education and meaningful careers. This means Utah’s fertility rate will stay relatively low compared to recent history.

What are the effects of lower fertility? There are positive and negative consequences:

Growth pressures on Utah’s public education system will lessen.

Some Utah industries that rely on rapid internal population growth will feel a tapering in consumer demand.

Pet stores may experience a surge in demand.

The benefits of Utah’s youthful workforce — such as a growing, inexpensive and tech-savvy labor force — may become less of a competitive advantage.

The ratio of workers to retirees collecting Social Security will continue to fall.

“There is something about modernity itself that tends toward fewer children,” says Last. He’s right. As society becomes wealthier, we have more choices. When it comes to childbearing, often the choice is, “I’ll wait another year.” This single choice will dramatically impact Utah’s future.