Northland's Ultrasound Specialists
Phone: 09 974 8844
21/50 Kioreroa Road, Port Whangarei, WHANGAREI 0110


Whilst you may get a positive pregnancy test before your period is even due it is a couple of weeks before the pregnancy is big enough to be seen on scan. In the early weeks how much we can see in very early pregnancy is different for every woman and every pregnancy.


At 4 weeks gestation (2 weeks after conception) when you have just missed your period we cannot detect the pregnancy on scan, all we can see is that the lining of the womb has become thicker. Somewhere between 4 and 5 weeks, we can sometimes see a small black fluid area in the uterus but we cannot confirm it is a pregnancy sac until we can see something growing inside it.


During the 5th week we can usually see a small pregnancy sac (around 6mm) and within it we can usually see a yolk sac. This confirms to us that this is definitely a pregnancy sac. Sometimes we can see a small white dot next to the yolk sac which is a very tiny foetus but at this stage we often can’t see the baby’s heart beating simply because it’s too early. This is why we try not to scan too early as it often causes a great deal of anxiety to the parents if we can’t confirm that the baby is alive and well.


Even at 6 weeks we sometimes struggle to see the baby and its heart beat even when things are going fine. At 6 weeks the baby measures approx. 4mm from head to bottom, this is called the crown – rump length or CRL and is the measurement we use to date your pregnancy in the first trimester.


At 7 weeks the baby can now be clearly seen measuring approximately 10mm in length. At this stage we should always see the heart beating in a healthy live pregnancy.


Wait one week more for your dating scan and see how much baby changes. At 8 weeks baby now measures 16mm in length and has a clear head and body. If you are lucky you can sometimes see the small arm and leg buds developing.


9 weeks and baby is much clearer still, with small arms and legs developing and often having a little wiggle on screen. Baby now measures apron 22mm long.


At 10 weeks and measuring 30mm even more of baby’s features are visible. Small hands and feet can now be seen and some of baby’s facial features.


At 11 weeks, baby’s head, body and limbs are getting clearer. Baby now measures 40mm from head to bottom.


At 12 weeks and all the baby’s organs are now formed. The face, skull and brain can be seen as well as the stomach, bladder and the limbs.


Around 19-20 weeks you will be offered an anatomy scan. At this scan we will be checking through baby from head to toe. Baby is now too big to measure from head to bottom so we will be taking measurements of the head, abdomen and femur length (thigh bone) to check how baby is growing.

Over the next 20 weeks baby just grows and gains weight. In many ways the baby gets harder to see on the scan as they take up more and more room in the womb.