It is recommended to have a diagnosis test, such as an ultrasound or blood tests, between 18-20 weeks of pregnancy. This allows for a comprehensive evaluation of your baby's development and can help identify any potential abnormalities or health concerns. As for the thyroid test, it is generally performed during the first trimester, ideally around 10-12 weeks. This helps ensure that any thyroid-related issues are detected early on and can be effectively managed throughout your pregnancy. However, it's important to consult with your healthcare provider who will guide you based on your specific circumstances and medical history.