Orthodontic treatment can be carried out during pregnancy, but with extra care. The biggest risk concerns the health of the gums, as pregnancy often makes women more prone to inflammatory conditions such as gingivitis. In some cases, the inflammation can worsen and progress to periodontitis, which is why it is essential for a periodontist to monitor the gums.
In addition, the hormonal changes that take place during pregnancy affect bone metabolism, which matters for how quickly teeth move. Because of these factors, teeth often move more slowly in pregnant women.
This answer is for general information. Your own case needs an examination by an orthodontist.