Pregnant Jill Duggar, Derick Dillard Celebrate 1-Year Engagement Anniversary, Eagerly Await Baby Dilly's Arrival!

19 Kids and Counting star and hubby conceived their first child almost immediately after saying "I do"

First comes love, then comes marriage, then comes a baby in a baby carriage!

Jill Duggar and Derick Dillard weren't k-i-s-s-i-n-g until the day they said "I do," but they wasted no time after that. Within two months of getting hitched, the 19 Kids and Counting star and her hubby announced they were expecting their first child. Baby Dilly's arrival is imminent (his March 24 due date has come and gone!), and soon life for Jill, 23, and Derick, 26, will be forever changed.

It's hard to believe, too, that the young couple has packed this many milestones into such a short time. After all, it was only a year ago that Derick proposed! The parents-to-be celebrated their 1-year engagement anniversary on Sunday by Instagramming two adorable throwback shots.

"One year ago today, she said yes," Derick wrote. "Happy engagement anniversary to my beautiful bride @jillmdillard I love you Jill Michelle! #newlyweds."

Jill was feeling the love, too. "One year ago today, the sweetest man in the whole world asked me to marry him," she wrote. "I said, 'yes, totally!'...now, 9 months into marriage we await the arrival of our little #babydilly."

Jill and Derick were engaged for less than three months before their June 21 wedding, after which they conceived almost immediately. The Duggar daughters and their fellas have to follow dad Jim Bob's courtship rules—one of which is no sex until the wedding night—so Jill's right-off-the-bat pregnancy raised some holier-than-thou eyebrows.

Fueling the speculation? The 19 Kids and Counting star posted a bump pic back in September holding a sign saying she was 13 weeks and 1 day pregnant (93 days) even though she'd only been married 90 days. Some people not familiar with how conception is calculated took this as an indication Jill and Derick had (gasp) premarital sex, but that's not necessarily the case.

E! News broke the numbers down on this already, but essentially, however many weeks along someone is in their pregnancy, subtract two weeks from that and you'll have a date close to when the actual conception took place. Based on this math, Jill and Derick conceived within the first two weeks they were married (which was still after vows were swapped)! She just happens to be quite fertile and he apparently has some strong-swimming sperm.

In any case, it's been a big year for these two, and just think: Any day now their greatest adventure yet will begin!