“American Sniper” is nominated for best picture at the Academy Awards this Sunday. It’s a gripping, controversial tale of war. But let’s be honest: Some people are only going to remember that fake baby.

If you saw the movie, you know the scene. War veteran Chris Kyle (Bradley Cooper) and his wife (Sienna Miller) are having a very tense conversation after he returns from Iraq. He’s holding his newborn baby girl — a baby that is laughably, obviously a plastic doll. It was a moment that utterly distracted and boggled many moviegoers. With a $60 million filming budget, why would a director like Clint Eastwood ever want to chintz out with a fake baby?

Well, for a lot of reasons. Babies are a booming industry in Hollywood, with many parents eager to get their kids started in showbiz. But filming babies is tricky, especially newborns. Even if using a doll looks a little ridiculous, it’s understandable why even distinguished filmmakers may take a pass on involving a real-life, breathing infant into the already-complicated process of shooting a movie.

Ask anyone who deals with babies on screen, and they’ll tick off plenty of reasons why a producer or director would prefer to cast a doll. A real-life baby, for example, must go through medical tests and be approved by a doctor before they’re allowed on set.

The biggest hurdle is time constraints. Though the rules vary by city and country, newborns are generally only allowed on set for about 15 minutes at a time, and under a certain amount of lighting. Not only does that inhibit the adult actors in the scene, but squalling newborns aren’t always exactly ready for their cue.

“That’s why, a lot of times, producers hire multiple babies — you can’t always guarantee a happy baby ready for filming,” said Toni Casala, founder of Los Angeles-based Children in Film. “And if one doesn’t show up, you’re definitely in trouble.”

It seems that something like that happened on the set of “American Sniper,” screenwriter Jason Hall explained on Twitter: “Real baby #1 showed up with a fever. Real baby #2 was a no-show.”

Sometimes producers can get around the timing rules by using more than one infant — twins or triplets, if they’re lucky enough to find a set. When the time clock is up on one baby, you can just swap out a new one. Still, multiple babies means multiple added expenses: Just like any star, newborns require an entourage, such as a nurse on set and other experts to ensure the infants are kept safe and everything is running smoothly.

As you can imagine, veterans of those showbiz infant entourages have some stories to tell.

“The worst thing I ever did was to teach a baby, ostensibly, to rub cocaine on her jaws,” recalled Dawn Jeffory Nelson, a Hollywood baby wrangler.

Once a baby is lawfully ensconced on the set, the issue becomes how to get them to do what the director needs them to do, whether that’s sleeping peacefully or crying loudly. Or other things. In Nelson’s case, the “cocaine” was powdered sugar, in a memorable and disturbing scene from “A Very Harold & Kumar 3D Christmas.” The script also called for the toddler to get high on marijuana (again: not really) so Nelson had to teach a 2-year-old to say “Whooaa” as special-effect smoke wafted around a car.

As a baby wrangler, Nelson is the person on set in charge of getting the best performance out of the littlest actors, and making sure babies are safe. Most of her work involves babies slightly older than newborns (California law prohibits babies on set younger than two weeks). She knows very well how difficult it is to coax a performance out of a baby of any age.

Babies often get so comfortable in an actor’s arms that they promptly fall asleep, just when a director needs them to cry. Solutions involve finding out the feeding schedule from the parents, and then waiting a few minutes past that to start filming; or simply clapping hands to startle the baby awake. The baby’s comfort remains key, though, so the the second the shot is over, they are immediately picked up, fed and comforted.

Nelson believes that while casting babies is complicated, it’s usually always worth it to make the film more realistic. She’ll only advise the director to go the artificial route if she thinks the scene might be too much for a baby, with tricky shooting angles or loud noises, for example.

“From my viewpoint as a wrangler, where I will go to a producer and say ‘spend the money on the most extraordinary fake baby you can,’ is going to be any situation where I feel that the shooting situations would be harmful,” Nelson said.

When a casting director needs a real baby, though, they cast a wide net, advertising in maternity wards or calling around to obstetricians. Parents sign up for exactly the reasons you’d expect: It’s never to early to make a bit of money for a college fund. Others are desperately starstruck, as Nelson found when working on “What to Expect When You’re Expecting,” where parents seemed eager for a story to tell about, say, star Chris Rock holding their little darling.

But moms and dads looking to cash in big should be warned that newborns rarely launch a lucrative career just by appearing on a TV show or movie. “For rare cases of the Olsen twins, that just doesn’t happen,” Casala said.

For London resident Sanna Pehkonen, getting her daughter into a movie just seemed like a fun thing to do. A couple weeks before she gave birth, she saw a flyer in the hospital that a few local TV shows were looking for newborns.

After Aili was born, Pehkonen called the number on the flyer with her questions: Would there be a medical professional on hand? Who, exactly, would be handling the baby? Would she be allowed to be on set? She sent in photos of Aili along with her measurements. Soon, she got a call: Would Aili be available to appear on the 2013 Christmas episode of the BBC’s “Call the Midwife”?

Pehkonen remembers the whole filming day as a very pleasant experience, and a welcome one that snapped her out of her post-pregnancy blahs.

“Mentally, to sort of improve my mental well-being, I just wanted to do something a bit out of the ordinary,” she said. “You’re tired and you stay back home and watch TV all day long. I just wanted to do something that would really jolt me out of that state.”

A car took Pehkonen, her husband and Aili to the set, where they relaxed in a private dressing room for several hours. When filming started, Aili had just been fed and remained calm through all three takes. She slept through the first two. During the third, she opened her eyes, yawned, and then fell back asleep again.

Aili was cast on one other show; in all, Pehkonen said they only made a few hundred dollars from her daughter’s brief film career. “The money was a nice addition, but the main motivator was to have a really interesting experience,” she said.

Terri Coates, the midwife adviser on “Call the Midwife,” said the show has filmed about 70 birth scenes over the years. (Season 4 premieres in the U.S. on March 29.) Unless it’s a particularly tough angle, they prefer to use real babies instead of dolls. For all those wee ones on set, Coates says it’s generally a calm situation.

“Newborn babies, as long as they’re warm and well-fed and person holding them is comfortable, tend not to cry,” she explained. “The baby’s in charge. What the baby needs, goes.” Sometimes, they’ll need to turn up the heat because of a baby on set, and the crew will just have to swelter in silence.

Even if it does take some more time and negotiation to bring a real infant to set, veteran baby wranglers maintain it’s always worth it. “American Sniper,” in particular, left some surprised.

“It shouldn’t have been too hard to find a baby to be honest, even at the last minute,” said Casala of Children of Film, about the “American Sniper” incident. “It’s surprising they didn’t take the time to re-shoot that scene, because it looked so bad.”