(Spoiler free section about why I gave my score and a small summary of the story. There's a warning further down for when spoilers start)
I really love realistic dramas, especially if they show real problems that are going on at the time it was made. Hot Mama had a lot of potential in that regard but unfortunately the characters, who should be the driving force, are the weakest part of the drama. I liked the business/company part of the story, but you can fast forward though most of the interactions because if you heard the opinion of a character once, it's not going to change. I would have given the story an 8, but I included the characters in that category, which pulled the score down quite a bit.
This drama is for you if you want a realistic drama about a married working woman but you don't care much if the characters are steoretypes or unreasonable. If you want to watch it because you want to see character development and/or you want to know the reasoning for their actions, you shouldn't expect much because you don't get any of it.

One of the themes of the drama, and the point I liked about it, is how it shows the problems a mother faces when going back to work after giving birth. We all know Japan has a real birth rate problem and the government doesn't seem to know what to do about it. Well, if these old men with their pathetic views of women would've watched this drama, they would've recognized one of the biggest problems as soon as they finished the second episode. The chances of a woman being promoted are already slim to none in a Japanese company, getting a private life on the side would make it downright impossible because of the chauvinistic views a lot of male dominated companies still have. But this drama shows an even more common problem. It's almost impossible in these times to create and sustain a family with one income. But it's also impossible in most companies for the mothers to go back to work after coming back from giving birth without colleagues/superiors belittling them. It was a pretty big milestone a few years ago when Japan introduced the right to take maternity leave without the fear of getting fired. In theory that's a real good thing. But in reality, as soon as the mother takes one step out of the company she's being replaced. When she comes back she'll probably start from zero in another department she never wanted to work at. Or if that doesn't happen, it'll be like it's shown in Hot Mama, with at least a few colleagues/superiors trying everything in their might to hinder a successful continuation of the mother's career.

(Spoilers ahead, mainly for characters and their (lack of) development)
This is going to be a bit long, so bear with me please.
Let's get to the big problem of the drama, the characters. Some people really like Motoya, but I really couldn't get over the first episode and the scumbag points he accumulated in it. Scumbag point number one: He definitely needs to learn some self-restraint. He really doesn't need to sleep with a drunk-out-of-her-mind-woman just because she comes on to him, especially not without contraception. Scumbag point two, which makes point one even worse, is that she rejected him a few times already (the first time was five or more years back), so it's definitely not ok to just "go with the flow of the drunk person" or just keep showing up at her apartment like a stalker. If this was a thriller I would have totally bought the old "sitting in a dark appartment and laughing like a mad man" theme while he made the plan to impregnate her so she would stay with him. He was really supportive of her and a real good guy later on, but that doesn't erase the fact that he was a real scumbag in getting there.
So, Natsuki was the victim, right? Well, she was just as much of an idiot the whole time. She's really competent at everything that comes with her job, but that's about the only good trait about her and she accumulated a few big stupidity points, especially at the beginning. First stupidity point, you don't message the person that obviously likes you for a long time and seems like he's as much of an adult when it comes to love as a middle schooler and then get lights out drunk so you don't even remember what happened the next morning. Second stupidity point, after the fact that she accepted her pregnancy and agreed to marry Motoya she keeps hanging around her elite ex in her private time and gets flustered every time he just looks at her. The whole time it seemed like if he would've asked to go to a hotel together she would've run ahead and waited for him there already naked. Please Mr/Mrs Screenwriter, if you want to create realistic characters stop using the old Shoujo Manga trope of the dumb girl that loses all of her common sense when the handsome, rich prince looks at her.

Enough of that, let's look at the supporting characters. Almost every one of them was either a walking stereotype or acted irrationally. Or both at the same time. Natsuki's direct superior was the stereotype of "if you want to be a career woman you are not allowed to show any weakness whatsoever or even smile", otherwise people would think you're "just a woman", even though most people in the company accept and respect career women. Then there was the stereotype overambitious, manipulating and throwing-stones-in-the-way-of-the-main-character colleague who has nothing going for her so she needs to use her "female charm" on the boss to advance in the company while she tries to destroy the main character's career without a visible reason. Speaking of the boss, he just hates working mothers (or working women who are good at their job overall). I really don't know why, but maybe his manliness is threatened, with his leather jacket and biker gang member characteristics. All his "arguments" (can't work the same hours as other workers, needs to take time off all the time, etc) are absolutely crushed immediately after Natsuki comes back to work because she achieves even better results than before her pregnancy. But that doesn't seem to satisfy him and he keeps putting working women who don't flirt with him down and tries to dissolve the baby department, even though it's probably the most profitable in the whole company. Natsuki's best friend is just the stereotypical supportive friend who tries to instill common sense into her. And last but not least is the stereotypical scumbag elite ex-boyfriend of Natsuki who does everything in his power to be the best homewrecker possible. He learns that Natsuki married and has an infant at home and immediately starts to hit on her. He knowingly uses all of her weaknesses (her love for her job/career and that she has maybe lingering feelings for him) against her and even asks her twice to accompany him abroad, even though he knows her daughter's only 6 months old. And to put the cherry on top he uses her lowest moment, when she learns that the department's going to be dissolved, she's probably going to be fired and she's crying her eyes out, to stop her and rather forcefully embrace her. Well done, Kuzu-ouji.
To end the review (rant) on a positive not, there are supporting characters who actually help make the drama more enjoyable. Natsuki's colleague, Nanbu, who's the honest guy that tries to support everyone while trying to win over Natsuki's best friend and the two other moms who are pretty funny and bring a bit of uniqueness with them.