My twins are already TV celebrities. They played 'Baby Jane Doe' on 'The Pitt' at 4 months old.

• Desanka Pinder's twins, Luna and Luca, signed with an agent when they were days old.
• They filmed Grey's Anatomy at 3 months, and The Pitt at 4 months.
• The babies can only be on set for two hours and film for 20 minutes each day.

This as-told-to essay is based on a conversation with Desanka Pinder, mom to Luna and Luca. It has been edited for length and clarity.

My husband and I used to joke about having twins. I liked the idea of having two kids and only needing to be pregnant once, but it felt like a pipe dream.

When I got pregnant, I suspected almost immediately that it was twins. My husband, David, and I went to a boutique ultrasound studio near our home in LA. Almost as soon as the wand touched my stomach, the technician delivered that infamous line: "Do twins run in your family?"

All healthy babies are a blessing, but having boy-girl twins felt even more rare and special. David and I are both models and actors, so we also knew that twins are in demand in the entertainment industry.

We interviewed agents during my pregnancy, and signed Luca and Luna with an agent within their first days of life.

There are lots of regulations about babies in film

The regulations for child actors are especially strict for babies. Luckily, our agent helped us figure out the logistics, including obtaining work permits for the babies (which required clearance from their pediatricians) and setting up special savings accounts for their earnings.

Luca and Luna are allowed on location for only two hours per day and can film for only 20 minutes. That's why twins are so popular with production companies: they can get double the filming time while coordinating with only one family. When we were on set for "The Pitt," there was another set of twin babies filming, too.

The twins were born in September and filmed their first scene on "Grey's Anatomy" in November. They did another scene on Grey's the following month, then booked two scenes on "The Pitt" in January, when they were about 4 months old.

Both babies were filmed in both shows, but Luna appeared on "Grey's Anatomy," and Luca on "The Pitt."

Watching my son film with Noah Wyle was surreal

When we arrive on set, we're greeted by the on-set nurse and teacher. They're an extra set of protection for the babies and extra hands for the parents. They helped change the babies and hold them while David and I took care of the paperwork. They also made sure we didn't exceed the twins' allocated filming time. It seemed like they tracked it down to the second.

I was amazed at how efficient filming was on "The Pitt." We were in and out of the studio in about an hour. We would get the babies dressed while the actors rehearsed, then bring one or both of them onto the sound stage.

Watching Luca film a scene with Noah Wyle for "The Pitt" was surreal. Here was an award-winning actor delivering a beautiful monologue while our son sat on his shoulder. Not only were we watching an expert at the top of his game practice his craft in real time, but our normally talkative, active baby fell asleep on his shoulder.

It worked out perfectly.

The twins recently did a commercial, and we plan to film more

We're raising Luna and Luca in LA, where we're privileged to have access to so many opportunities. We might as well take advantage of them. We want the babies to be as successful as possible in life, and this is one way to help with that. It also helps build their financial future.

Bringing the babies to set has been a way for me to bridge my passion for acting with parenting. Sometimes being in the newborn trenches is difficult, but David and I have forced ourselves to get out of the house. Ultimately, I think that made it easier for us to adjust to life with twins.

Filming with the babies has reminded us about who we are and what we love to do. We have amazing memories of being on set together, and we will have this unique professional documentation of the twins' babyhood. The twins just filmed a big commercial (I can't say for whom), and I hope they'll have more bookings.

As long as we're all still having fun, we'll keep filming.