She tries to hide it for as long as possible, it's her business and she knows they will kick up a fuss when they find out. But she cannot keep it a secret forever, eventually the looser shirts she's been wearing to work won't hide the ever growing bump. She has her reasons for not telling them. Mainly because of the inevitable insistent questions she will get for the rest of her life about who the child's father is, a question with an answer she doesn't feel the need to share with anyone and everyone, especially not a team of superheroes. All they needed to know was that her and the father made a mutual decision for him to not be involved in his child's life.
When the time for keeping it a secret passes, she tells the team as such: this did her business and the only time they'll ever see her child is when it's still inside of her, she doesn't want a group of superheroes getting overly attached to her baby. If course, looking back, she knows that their love for Tabby was inevitable and probably impossible to prevent. The minute they find out they establish what roles they will have in her child's life: Tony immediately offers financial services, the only way he seems to be able to show affection; Thor is loud in his congratulations and promises of protection from all kind of mythical beasts she has never heard of; Clint and Tasha seem overly excited about the prospect of passing down their skills at sneaking to make her child the best hide and seek player ever, she knows they struggle with their inability to have children behind their marks of solidity. Bruce timidly hands her a book on yoga at one of their team breakfast meetings, his nervous explanation that he heard yoga was supposed to help pregnant women genuinely making her smile, despite her awful morning sickness. But then there is Steve.
The two of them have been dancing around being something for months. They exchange small touches that just creep over the line of being casual; his hand always seems to find the small of her back whenever they and up next to each other, he walks her out of the tower when they have a meeting last thing, a kiss brushed on her cheek as he whispers goodbye. They've even been for coffee a few times. They are so close to being an actual, functional couple that Steve automatically slips into the role of father when he finds out she's pregnant. He starts to appear at her office at Stark Tower with food and her one allocated coffee of the day (this kid better be grateful for the caffeine she has to give up when carrying it around for 9 months) as if he somehow knows she didn't manage to keep anything down that morning. He forces her to go home at a reasonable hour, even bringing ice cream when she calls him in the ludicrous hours of the night. At first she resists, she doesn't need help, being pregnant doesn't make her an invalid. But as time goes on and she gets bigger and they become closer, she lets him look after her. It's actually a relief to have someone to rely on, someone who actually cares about how she feels; so when it comes round to her next doctor's appointment, she asks Steve to go with her.
It's actually adorable how nervous he is about it. As they sit in the waiting room he wrings his hands and bounces his leg so much that she has to put down the magazine she is reading to calm him. She gently places her hand over his leg, stilling it instantly with the contact. His large, calloused hand finds hers and he traces the tiny lines of it, lifting it up so that he can study it and learn even more about her. He is so completely focused on her hand that he misses the nurse calling Maria's name; he looks surprised when she rises from the uncomfortable plastic chair and tugs on his hand. She can tell he is anxious about this, she is too. She has always attended these things by herself, asserting her independence. If the doctor is surprised to see Captain America in her office, she doesn't show it, she merely continues with the tests just as she has in every other appointment.
Steve looks like he is going to faint when Dr Adams shows the ultrasound on the screen.
Of course he's seen the pictures before, he even asked for copy to put in his wallet last time, but watching the tiny life in real time and hearing its little heartbeat reverberating around the room nearly finishes him off. He doesn't stop gushing about the whole experience at dinner with the team that evening, the one he forces her to attend almost every night now. Of course Steve couldn't make her do anything she doesn't want to do, but when he looks at her with hope and expectation in his beautiful blue eyes, she can't say no.
She also can't say no when he asks her to move in with him.
She is hesitant to accept at first, but even she has to admit it makes sense. Her apartment is alright for her, she only eats and sleeps there, but it's not suitable for a small child. His apartment at the tower would cut her travel time down to all of 30 seconds and he does have several bedroom sitting uselessly empty. Of course one of the drawbacks to living in the Avenger's tower is the thought of Tony appearing out of thin air at any given moment, but she's pretty sure that J.A.R.V.I.S likes her enough to help her round that issue. She also scared of what this means in terms of her and Steve. He offered her his two spare rooms, meaning one for her and one for the baby that will painfully emerge from her body in a matter of months, but she is aware that is he is sleeping just the other side of the wall she might not be able to resist. She blames it on the hormones, but she can't help but imagine falling to sleep wrapped in his safe, warm arms that protect her and the innocent life she carries. She knows that she could very easily love him, that she does love him; but that doesn't mean that she should. So when she eventually says yes, it is not only a yes to moving in, but a yes to letting herself love him.
She moves in two months before the baby is due.
She moves her stuff into his room a month and three weeks before the baby is due.