Sleep deprivation can do funny things to parents. Nighttime nanny Kristin Smith has seen it all. One dad rocked a pillow to sleep, thinking it was his baby. A mom nodded off while pumping breast milk for her preemie. Some are so exhausted they slur their words or become extremely emotional. That’s when Smith gently steers them to bed and takes over.

As proprietor of Boston-based Nightingale Night Nurses, her agency provides overnight newborn care, hands-on sleep coaching and postpartum support. Much of it is based on her experience as a nanny and raising her own daughter, but she also employs a team of baby nurses, postpartum doulas, and family-wellness supporters. While night nurses were long a practice in aristocratic families throughout the ages, changing attitudes about child care emphasized independence and self-reliance.

But the demand for ­overnight help has increased as more families have both parents working outside the house.

“I like to joke that I have hundreds of surrogate children in the world,’’ said Smith, 34, who counts 37 sets of twins among the many babies that she has attended to. She or another night nurse arrives between 9 and 10 p.m. and stays throughout the night, working an 8-12 hour shift with a flat rate of $300 for a single infant and up to $540 for triplets.

“We lay down in the same room as the baby, so our heart rate lowers, and the baby picks up on that. It sets the tone for a healthy sleep environment. We’re not sitting there on our phone or working on a laptop.’’

Hazards include dads who sleep naked, fights between ­exhausted parents, and odd ­requests such as the mom who wanted to share a bed with her and the baby (she said no.)

“I love working with babies. They don’t talk back; there are no co-workers to deal with, and they need and love you. I started when I was a sophomore in high school; my new brother-in-law was having a fourth child and their au pair was leaving. They asked if I could be a nanny for the summer and that’s when I fell in love working with kids. After I graduated from high school, I became a professional nanny in New York. I was making $800 a week, with holidays and sick days off and other bonuses – and a car. It was better compensation than anyone else my age was making.

Ultimately, I ended up working for eight different families. Then, when I got pregnant with my daughter, just before turning 20, I was fired because it was an inconvenience to the family I was with at the time. I found two other part-time positions and ended up going into labor at one of the houses. The mom didn’t quite understand that I was having contractions and wanted me to run an errand to the grocery store. I told her, ‘No, you get the food, I’m going to the hospital.’

After my daughter was born, I decided to relocate to Boston and began a solo practice as a birth doula and overnight newborn-care specialist. It was then that I realized families with newborns need help desperately. I had a knack for getting babies to sleep: as long as they’re full, warm, and dry, they’re usually happy. I was winging it in the beginning, to be perfectly honest, but now I create safe sleeping spaces for babies based off of the most recent guidelines from the American Academy of Pediatrics.

I started my own nighttime nanny agency two years ago. We make sure a trusting relationship is built with one caregiver, whether it’s just for one overnight visit or six weeks or more. Some babies can be challenging — they’re colicky or have medical needs. Preemies need extra care, and multiples are exhausting. Right now I’m working with a single mom by choice who used a surrogate. She’s been on an emotional rollercoaster, waiting so long for this baby. She has a busy career and doesn’t have a partner to help her at night, so we are there for her.

My favorite saying is, ‘We get up at night, so parents don’t have to.’ Still, I need my rest too, so after work, I go home and nap on the couch with my pup. I’ve trained my body to only wake up for a baby. You could be doing construction in the next room and I would sleep through it.’’

Cindy Atoji Keene can be reached at cindy@cindyatoji.com.