When a later scan gives a different estimate of gestational age, the estimated age is not normally changed but rather it is assumed the fetus is not growing at the expected rate.
Anomaly scan and fetal sex determination (20 weeks scan) This scan is a routine scan in the UK which takes place at around 20 weeks.
It can also help to diagnose abnormalities or problems, help determine the age of the pregnancy and subsequent due date as well as showing the position of the placenta in relation to the birth canal.The Royal College of Obstetricians & Gynaecologists (in their 2000 document on Ultrasound Screening), recommend an Early Pregnancy Scan, undertaken before 15 weeks, which can combine the functions of the Early Viability Scan, Nuchal Translucency Scan and dating scan. These two scans are the ‘minimum’ number of scans required during pregnancy and are offered by ¾ of ultrasound units in the UK.Measurements of the fetus will also be taken to ensure it is growing normally.At this point, should you wish to know the sex of your baby, you can ask the sonographer to tell you.If you have had any bleeding or pain or any other symptoms then this scan will accurately confirm viability.
Early Pregnancy Scans are not routinely offered on the NHS but you may have one privately without affecting your NHS entitlement.For all Obstetrics scans, no special preparation is needed, although it is best to wear loose clothing that can easily be lifted or removed in order to expose your abdomen.You will lie on your back on an examination couch and the transducer moved back and forth across your stomach in order to gain the best possible image of the fetus.If a potential problem is indicated, a further follow up scan may be needed.If this does occur, the possible complications of or implications for the pregnancy will be fully discussed with the parents by a doctor or consultant and advice and guidance will be provided.Ultrasound imaging in pregnancy is widely used to evaluate the baby.