Categorized | Baby Care

How big is my baby? Size measurements during pregnancy

Posted on 05 December 2016 by hulda

It is common for people nowadays to have ultrasound.  I am as guilty as any private practitioner in Hong Kong, of doing too many ultrasounds for pregnant women.  They are simply not needed, often give us more doubts and questions than they are solving problems and reassuring.

The pregnant mum does not know this.  Nor the dad.  They usually either ask, or are happy to see the baby moving there on the screen and everyone gets mildly addicted to seeing the little individual that now seems to look like the family, wink and kick back during the ultrasound.

Not everyone feels this way, some parents ask for less ultrasound.  They are, like myself, slightly worried that one day, even if modern research does not seem to support it, that one day ultrasound will be deemed less than good for unborn babies.

Still, we do so many ultrasounds.

I did an ultrasound course in the Chinese University of Hong Kong, as a postgraduate training.  I learned a lot.  Amongst other things I did learn that:

Size of baby during pregnancy

Size of baby during pregnancy

  1. Routine ultrasound for healthy women in low risk singleton pregnancy is not recommended except for around 12 and 20 weeks.
  2. Other times, if there are twins, low placenta, unusual growth pattern, diabetes etc, there is a reason to add more ultrasounds into the checkups, usually with at least 2 weeks in between, otherwise it is not considered accurate information.
  3. It is considered safe to do the ultrasound with a regulated machine by a person who knows how to use it, but it should be as short as is needed for each checkup.
  4. Routine palpation and fundal height measurements for baby’s growth pattern and size has very similar accuracy as doing an ultrasound as a routine to get this same information, both with around 500 gram give or take accuracy around third trimester.
  5. Head size measurements for low risk pregnancies, and how engaged the head is, is not recommended practice as it is both very inaccurate and carries little value in evaluating if the birth will be normal, easy, long or short.
  6. Measuring the baby’s abdominal circumference in the 3rd trimester  with two weeks between, is most likely to give accuracy on the growth of the baby.
  7. Telling women that they have a big baby will increase their fears a lot for the birth and the term “big baby” is widely used in a non-professional way.
  8. A normal healthy baby is somewhere between 2.9 to 4.0 kg. Around  3.4 kg is average for Caucasian babies and 3-3.2 kg for local Hong Kong babies.
  9. There can also be good reasons for babies to be 4 – 4.5 kg,  and some women have no problems giving birth to them.  It is important to exclude diabetes, but otherwise in some families this is normal size.
  10. Size measurements and ultrasounds can very important and needed for some pregnancies. Some pregnancies are more high risk than others and ultrasound can give more accurate and appropriate information than some other methods.  Therefore, it is important to use the ultrasound appropriately and wisely.

I learned a lot more.  This is just from the top of my head now, as I have been asked several times if I can measure size of babies.

Well let me share that in our practice, generally, we use the NICE guidelines and do 12 and 20 week ultrasound by a recognized radiographer, midwife or doctor that is specialized in these checkups.  If during the rest of the pregnancy, we worry about the baby’s size, I sometimes do an ultrasound myself to see if it seems to confirm it, but usually I send people off to a specialist to do further assessment.  80 percent of the time, the result is still within normal limits.

Hulda Thorey – midwife

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