Question: I know that week’s gestation is on prenatal records, but is it required to have what trimester the patient is in at the time of visits? Virginia Subscriber Answer: You can calculate the trimester based on the week’s gestation at the time of the visit. You have to know which trimester before you can pick the right code, so if you are using an EHR, you should be sure that this information is captured in the same place each time. But the provider does not need to stipulate the trimester if you have week’s gestation; someone simply has to calculate it in order to select the correct code if the provider does not select it themselves.