Firstly, during the first trimester of pregnancy, mothers should avoid hair colours that come into contact with the scalp.
This is not just to keep chemicals off the skin and therefore entering the body. When using colour products directly on your scalp in this stage they can react with the hormones in your skin, heat up in ways that are irregular and the colour you’ve been getting every time you retouch your hair will come out completely different at your roots.
This won’t happen with foils luckily. You can get your highlights retouched as regularly as normal. But with an all over colour in the first trimester (and I’d recommend during your whole pregnancy and if you decide to breast feed) stick with a semi permanent if you have grey hair you need to hide, they have less or no ammonia compared to tints, and avoid other chemical treatments.
Secondly, you need to know about hair loss.
Once, a few months after one of my clients gave birth, she called me super stressed out because she was losing clumps of hair. Scared to brush it or wash it incase she was making it worse. I told her to treat her hair as normal as treating it delicately wouldn't change a thing.
Throughout the duration of your pregnancy you may notice your hair getting thicker. This is common during pregnancy but doesn't happen with everyone and the degree in which it happens varies between pregnancies and people.
The way this seems to work is that, instead of losing the average 100 hairs a day (as a rule, refer back to Hair Loss blog) your body retains that hair and around 3 to 5 months after you've given birth, all that hair that you retained starts to fall out rapidly. If you're pregnant and your hair has gotten a lot thicker enjoy it while it lasts as unfortunately the hair loss is unavoidable. But don't worry, it will all come back. it all starts growing back and you'll notice short hairs sprouting all over the place and then you'll have your hair back before you know it. It may come back a little different depending on how your body copes with all the changes. The case will be different for everyone. Hormones are very powerful.
In the case of my stressed out client, her hair has grown back completely. Nothing to worry about.