When do you notify your boss about your pregnancy, maternity leave if you have been there for 1-2 years?

Hey! I want to give a detailed answer for this question, as it will touch various aspects.

1. Freezing eggs / embryos -> The process of doing this will be a bit invasive and will entail hormonal changes. Does your company help cover you for a portion of costs for fertility treatments? If yes, use that option. In my experience, from my colleagues who have done this, had an understanding with their manager that they are in the process of egg freezing, but did not take many days off. Maybe a week or any sick days as needed. This will have minimal effect for time away from work. But you may need to be mindful of keeping your workload manageable, and delegating when possible.
2. Pre maternity leave -> I would give heads up in second trimester, month 5-6. To enable smooth transition and develop trust.
3. Maternity Leave -> I took 4.5 months off for my maternity when I was at Netflix. We got 1 year paid parental leave, but I put pressure on myself to get back in 4.5 months. In hindsight, that wasn't the best decision. I wish I had taken longer. 5 - 6 months is ideal. Second trimester is when usually most women feel most active, use this time to set up your home, hire nanny, find daycare, baby proof the house, meal prep and freeze, take classes for birth, breastfeeding and spend quality time with your partner.
4. Early Motherhood -> Motherhood changed me. I became a leader, extremely confident, more empathic and I ruthlessly prioritized. All these are great goals for career growth. If you are comfortable, you can gradually get back to work after 5 months, and set expectation that you will work 20 hours per week for month 6, or share that you will gradually get back in. Take all the help you can get, either family, friends, paid. Do not skimp on a nanny, doula, therapist, and couples counseling ( if applicable) . Let your body heal, don't worry about losing weight.
5. Things do get easy with a child and life gets to be wonderful! Your perspective on what is important, and who are important will change.

So I'm not a mom and never will be, but I've generally found that the best approach to taking leave is transparency (especially if you like your manager). An employee going on leave is disruptive, so giving a heads up as soon as possible gives all parties time to plan around it.

When my favorite manager at Meta went on maternity leave, she told me 2 months ahead of time so me and the other tech leads could set up a plan to uphold the team in her absence (we totally crushed it too and got great feedback from my skip). Kuan in particular has a lot of great tactical advice here: "Is it good to take all your PTO at Google/FAANG companies or will you have issues getting a promotion?"

When it comes to balancing motherhood and work, here's an excellent thread: "How to keep my mental health while working in a competitive team and having kids?"