Tully

You might want to give your mom a great big bear hug upon exiting the theater after watching Tully, a sharply observed tribute to maternity that never settles for cheap sentimentality or melodramatic tear-jerking.

That’s because this third collaboration between director Jason Reitman and screenwriter Diablo Cody (Juno) — and their second with star Charlize Theron (Young Adult) — effectively transitions to more mature subject matter while retaining a playfully acerbic edge.

Still, this frequently hilarious and heartwarming comedy shows plenty of affection for the rigors faced by mothers, from a diaper-changing montage to breastfeeding close-ups to lingering shots of an exaggerated baby bump.

Theron stars as Marlo, who’s expecting her third child with husband (Ron Livingston), including a son with special needs that lead to him being labeled “quirky.”

Sensing potential burnout, Marlo’s well-to-do brother (Mark Duplass) offers a unique gift — the services of a “night nanny” who arrives in the evening and cares for the child overnight, allowing the parents to get some sleep. The initially reluctant Marlo eventually solicits help from Tully (Mackenzie Davis), whose arrival turns out to be a godsend.

As a modern-day Mary Poppins of sorts, Tully not only bonds with the infant, but she cleans the house and bakes cupcakes as a bonus. All the while, she insists she’s there to help the parent more than the youngster, with Marlo eventually relying on her as a sounding board while dealing with a midlife crisis, symptoms of post-partem depression, and a host of stressful decisions. It’s only after Marlo lets down her guard that she realizes it might all be too good to be true.

Theron’s fearless performance generates sympathy while meshing seamlessly with Davis (“Halt and Catch Fire”) as their characters’ journeys take unexpected turns.

Cody’s screenplay is sensitive yet sharply observed, probably in part because she’s a mother of two herself, and it manages to convey a sense of empathy without providing false hope or easy solutions for its beleaguered characters.

Contemporary parenthood is indeed difficult, it argues, especially when you have more children than perhaps your lifestyle, family structure, or financial situation can reasonably support.

A clever if mildly manipulative third-act twist doesn’t reduce the emotional impact of the material, even if it slightly muddles the overarching message. Through it all, Tully feels authentic beneath the surface, refreshing familiar themes with new life.

Rated R, 96 minutes.