Pregnancy dating and viability
Ultrasound scans offer an alternative method of estimating gestational age.The most accurate measurement for dating is the crown-rump length of the fetus, which can be done between 7 and 13 weeks of gestation.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.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.Parents often find that coming for an ultrasound scan at this stage in pregnancy is reassuring especially if there has been some bleeding.
Pregnancy Dating Gestational age is usually determined by the date of the woman's last menstrual period - assuming ovulation occurred on day fourteen of the menstrual cycle.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.However, in early pregnancy (less that 7 weeks), it may be necessary to perform an internal scan (transvaginal scan) to obtain clearer images of your baby and its surroundings.The Ultrasonographer carrying out the scan will give you a clear explanation of the procedure before the examination and will explain what they can see on the monitor during the scan. After the scan you will be given a report of our findings and the Ultrasonographer will explain what you should do or who you should see next in your pregnancy. We will give you a report, pictures and a DVD (over 12 weeks) free of charge of your scan.