As your baby grows, your doctor can do an ultrasound to measure your baby’s size. This will provide the doctor with a better view of the baby’s development, which will allow the doctor to estimate a due date. This due date will be more accurate in early pregnancy than those based on your period because it’s connected to the baby’s development in the womb. Ultrasounds can be done as early as five to six weeks after the mother’s last period. This is the best time to estimate your due date using an ultrasound. Before eight weeks, the baby's growth is hard to measure. After eighteen weeks, it's normal for babies to develop differently on the baby's own unique timeline. Your doctor will need to be able to apply the ultrasound wand to your stomach in order to view the baby. You may have to remove your clothing, though your doctor could allow you to just adjust your clothing if you wear an outfit with two pieces. For example, you could lift up your shirt to expose just your stomach. You will need to remove any clothing and jewelry that may interfere with the transvaginal ultrasound, and the doctor will provide you with a gown. A wand will be lubricated and inserted into your vaginal canal to get a closer look at your uterus and baby.  Your doctor may order a transvaginal ultrasound to get a more complete view of the uterus if it's early in the pregnancy. They may also order one if you have a high risk pregnancy or if there may be problems with your baby.  Your doctor will have you empty your bladder just before the transvaginal ultrasound is performed. Ultrasounds usually work best if you’ve have a full bladder, so drink plenty of water before your visit to the doctor. Up to six glasses of water may be recommended. Ask your doctor if it’s okay to eat before your ultrasound, as sometimes it’s best to stop eating a few hours before the exam. Your doctor can best estimate your due date if they are able to use both the date of your last period and your ultrasound. Using these two pieces of information, your doctor can...

TL;DR in Indonesian:
Buat janji dengan dokter. Mintalah pemeriksaan USG selama minggu ke-8 sampai ke-18. Kenakan pakaian dua potong yang longgar dan mudah dilepas. Bersiaplah melepas seluruh pakaian untuk USG transvaginal. Minum cukup air untuk mengisi kandung kemih. Sampaikan kapan haid terakhir Anda.