Why ‘War’ Wrote Serena Byrne Actress Phoebe Fox’s Real Life Pregnancy into the HBO Show (But Kept Sienna Miller’s Recent Pregnancy Under Wraps)
HBO‘s new legal drama War relishes in upending our expectations at every turn. Case in point: it’s not immediately apparent that bullish attorney Serena Byrne (Phoebe Fox) is pregnant when we meet her all the way back in Episode 1. However, as the series goes on — and Carla Duval (Sienna Miller) and Morgan Henderson’s (Dominic West) divorce intensifies — Serena’s bump steadily grows under her chic designer office wear.
Serena’s pregnancy wasn’t originally part of series creator George Kay‘s plan for the character, but came about when star Phoebe Fox revealed that she and her husband, Slow Horses Season 6 breakout star Kyle Soller, were expecting their first child.
“I talked about it with George [Kay] and they very much left it up to me: Did I want to have it written in? We could hide it,” Phoebe Fox told DECIDER. “You know, that was my choice.”
“And I said, ‘Look, it’s so rare to see a character on TV, a woman who is pregnant, and it is not the story.’ Fargo is really the only example I can come up with,” Fox added. “I think it’s really important for women to see that and to have it normalized. I wanted to really look after her pregnancy and make sure it felt realistic without giving it too much air time, honestly.”
The irony, though, was that Fox wasn’t the only War Season 1 actress who was pregnant during filming. Sienna Miller was also pregnant with her third child (and second baby with fiancé Oli Green).
“The other secret, I’m not sure you know, but we’re now allowed to talk about is that Sienna was also pregnant in parallel,” War director Ben Taylor revealed. “So she asked, ‘Could you write it in?’ and we had already said yes to Phoebe, so.”
“You can’t have all the characters —” George Kay said.
“You can’t all be pregnant and so with Sienna it was like the classic blocking where there’s handbags being held and desks are higher than perhaps they should be.” (And jackets are baggier than they necessarily need to be.)
Sienna Miller confirmed to DECIDER that “Phoebe got in there earlier than I did by saying she was pregnant,” but she now doesn’t know “if it would have worked” to have both Serena and her client Carla pregnant at the same time in War Season 1.
“Obviously we were both actually pregnant in the filming of this,” Miller said. “I think for [Morgan] to divorce [Carla] pregnant would be, would be really —”
“Well, this [could be] someone else’s baby,” Dominic West suggested.
“That’s true,” Miller said. “They could have had fun with it… But it was nice both being pregnant on set because we could commiserate and share chocolate.”

In fact, if you notice that Serena has a particular penchant for snacking in Season 1, that also came organically from Fox’s pregnancy.
“I said to George, ‘Look, all I think about all day is snacks. All day,’” Fox said. “So I say, ‘Look, I want to snack all the time. I think let’s put that in there.’”
As War Season 1 continues, you’ll notice the natural evolution of Serena’s pregnancy, which was ironically difficult to capture because of the out-of-chronological order logistics of television production. Adding to the challenge? They couldn’t rely upon prosthetics for continuity.
“This probably doesn’t reflect well on me, but I did investigate the concept of a prosthetic to sit on top of a bump. And we spoke to prosthetic designers and they said, ‘We’d never do that because it’s too dangerous,’” Taylor said.
“So we sort of just went for it. And we’d occasionally get notes from HBO and Sky, and it just meant that you went tighter coverage to hide it. But for the most part, you went with it and Matt, the costume designer, sort of embellished it.”
New episodes of War premiere on HBO and HBO Max at 9 PM ET on Thursdays.