It is common for first-time mothers to not feel their baby's movements until around 20-25 weeks of pregnancy. However, every pregnancy is different, so it's important to pay attention to your body and consult with your healthcare provider if you have any concerns. At 18 weeks, the baby is still relatively small, and their movements may not be strong enough for you to notice. Additionally, factors such as the position of the placenta or excess weight can also affect how soon you feel those first flutters. If you have had previous pregnancies or are experiencing any other symptoms like bleeding or severe cramping, it's best to reach out to your doctor for further evaluation. Otherwise, try not to worry too much as feeling the baby move will likely happen in due time.