It’s CLANNAD: After Story episode 15, and it’s all Nagisa’s pregnancy all the time. However, Nagisa’s sick health causes the doctors and Okazaki pause as to the whens and hows and even the ifs of Nagisa giving birth.
Okazaki suddenly has a lot to worry about as he is both concerned about whether his job will be good enough to support 3 people, as well as the fact as the pregnancy causes Nagisa to be frequently sick and bedridden.
Nagisa also insists on giving birth at home – something which Okazaki has concerns about. He asks Akio and Sanae, and they reluctantly agree to it, pending Nagisa’s health. However, the doctors increasingly worry about Nagisa’s health, fearing that the worst might be possible during the birth, and that it is recommended that the birth take place at a hospital.
Akio then takes Okazaki to his “secret playground” – the place he’s been running off to mysteriously before. He then tells Okazaki the second untold half of the story of when Nagisa collapsed and almost died when she was younger: the following morning, all hope seemed to be lost, and Akio sudden grabbed Nagisa and started running aimlessly with her. Eventually he happened upon a grassy field in some woods and prayed for Nagisa’s health there. Nagisa then woke up and eventually got better, and Akio says he’s been looking over the place (where they are now constructing a hospital) ever since. He explains that not everything one prays for will happen, and the one with the greatest risk has to be the one to decide what to do, but they’ll all find a way to get through it.
Finally, Nagisa decides to name the baby Ushio, partly because it can be used if it’s either a boy or a girl.
We resolved one foreshadowed event in this episode, finally finding out where Akio was running off to mysteriously. Howevrer, this episode also doused us with a heavy dose of Nagisa-won’t-survive-the-birth foreshadowing as well.
Also, you can tell that the series has taken a turn for the heavier when there is a scene where abortion is briefly discussed, even if it isn’t mentioned by name. This is on top of the fact that marriage and pregnancy aren’t exactly topics one normally sees in any type of anime series (at least ones as lighthearted as CLANNAD is, or at least was).
It’s not really said how far along Nagisa is by the end of the episode, but given that she can feel the baby kick, it’s probably at least in the 4th or 5th month of the pregnancy (even though she’s still rather small – or else she’s hiding it well). Also, apparently it can usually start hearing things – also mentioned by Sanae – around the 4th month – so I guess we can pretty much conclude that this episode covers roughly the first half of the pregnancy. I’m guessing it’s likely that the next episode will cover the last half, leading up to the birth either at the end of the episode or in the immediately following episode.