Chicago Fire has not skimped out on the action in season 13. The firefighting drama has been jam packed during the second half of the season, in particular, and the episode "Cut Me Open" kept up this breakneck pace. SPOILERS ahead!
The episode opened with an excited and slightly nervous Stella Kidd (Miranda Rae Mayo) and Kelly Severide (Taylor Kinney) discussing their plans to adopt a child with 51 co-workers. Herrmann (David Eigenberg) gave them some much-needed words of encouragement, which makes sense given that he's a dad to five children, but these firefighters charted different paths shortly after.
Kidd and Severide thought they still had weeks before the woman, named Jade, who planned to give up her baby for adoption was due. Jade was under the same impression, as she'd yet to get through the entire adoption process before she suddenly went into labor. She was going to have to meet with the 51 couple while she was in the hospital, and determine in real time whether they'd be the right fit for her unborn child.
Herrmann has to contend with potential 51 firings

Herrmann, meanwhile, had to pick up the slack for a shockingly thin 51 team. Not only were Kidd and Severide MIA, but Sam Carver (Jake Lockett) was working part time and therefore absent during this shift. Chief Dom Pascal (Dermot Mulroney) decided to take a personal day, and medics Lizzie Novak (Joceyln Hudon) Violet Mikami (Hanako Greensmith) were nowhere to be found either.
Normally, this would be a minor inconvenience, but Herrmann had to contend with a performance efficiency expert who had a reputation for playing hardball when it came to department cuts. This expert had reportedly gotten a firetruck decommissioned at Firehouse 28, so Herrmann was pretty understandably stressed to justify the worth of everybody he worked with (despite their absences).
Dr. Hannah Asher (Jessy Schram) eagerly greeted Kidd and Severide earlier in the episode, but her presence truly came into play when she has to deliver some upsetting news to the couple. It turns out that the woman carrying their potential child has a history with opioid addiction, and used them as recently as two days prior to coming in. You can see the wind get knocked out of both Kidd and Severide, and visible concern for what this will mean, medically, for the child.
Kidd and Severide reconsider their decision to adopt

While Asher focused on the pregnancy itself, Kidd and Severide discussed the repercussions of taking on a child with compromised health could mean. Kidd was emboldened to move forward and look after the child regardless, but Severide was unsure. He pointed out that him and Kidd have very busy workloads as firefighters, which led to a bombshell being dropped by Kidd.
Upon meeting with Jade, and receiving confirmation that they have been chosen to adopt the child, Kidd revealed that she has struggled with addiction herself in the past. She didn't get much time to delve into specifics, however, because Jade's water broke, and Dr. Asher immediately determined that an emergency C-section was needed.
Meanwhile, the efficiency expert tailed Herrmann on a call involving a man trapped in a vent. Herrmann and the team managed to get the man out safely, but the expert questioned why the firefighter changed his plans up in the midst of the rescue. Herrmann, with some help from Jack Damon (Michael Bradway) and Darren Ritter (Daniel Kyri), managed to turn the tables on the expert through a series of grueling firehouse drills.
The Chicago Fire couple goes home empty-handed

The expert tried to keep up with 51's finest, and wound up passing out from heat exhaustion while Herrmann and the rest of the team went around looking to purchase a carseat for Stellaride. It was fun to watch the team band together for such a worthwhile cause, while at the same time getting a leg up on someone who didn't seem to appreciate the sacrifices they make on a regular basis.
Jade's C-section proves a success, in so much as the baby is born healthy, but Jade herself was put on anesthetics right away due to a sudden drop in blood pressure. Sadly, Dr. Asher confirmed that the baby had tested positive for opioids, which meant he needed to be hospitalized. In yet another tragic yet understandable turn, Jade decided that she no longer wanted to give the baby up for adoption.
Kidd was heartbroken upon learning that Jade changed her mind. The efforts of the 51 team, who purchased a carseat and various toys for the baby, were in vain. At least, in the immediate future. The team comforted both Kidd and Severide, assuring them that they'll save the toys for when the couple do adopt. Their story isn't over.
51 didn't fare much better, sadly, in their subplot. The expert determined that the team is capable, but broke the news that employee cuts will be made regardless, per the fire department. Herrmann and Mouch (Christian Stolte) were pegged as the most likely cuts due to their age, which sets up all kinds of stress for them (and us) over the next few episodes. But this story is over.