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Counties Manukau Health Birthing and Assessment (B & A)

Public Service, Obstetrics and Gynaecology, Maternity, Maternity/Birthing Facilities

Slow Growth in your Baby

You may be asked to come to B & A to see one of the doctors because your baby is small. Sometimes you will see a doctor for the same reason in one of the antenatal clinics.

Some babies do not grow as well as we would expect for your build and ethnicity. A lot of work has gone into software that lets us make a grow chart which tells us the average size for you. Using this we can see how your baby is growing.

When a baby is not growing well this is called ‘intrauterine growth restriction’.

This can be caused by:

  • too little blood supply to baby through the placenta
  • a problem with the baby.

Having screening tests (link) and an anatomy scan around 20 weeks can help tell if there is a problem with baby. After that further scans may be advised (link to OGUS).

If there does not seem to be a problem with the baby then the placenta is the likely cause. There are a number of reasons why this happens:

  • you are a smoker – this causes restricted blood flow in parts of the placenta so only part of it works properly. If you stop smoking before 16 weeks you can stop this being the problem
  • you have high blood pressure starting in pregnancy – the blood pressure is because the placenta did not implant well at the beginning
  • you have high blood pressure before pregnancy
  • you have diabetes – not all diabetic women have big babies. For some their baby is really small
  • obesity – some obese women have good size babies but some have growth restricted It can be difficult to feel baby's size and often regular scans are recommended
  • anaemia – this can limit a baby’s growth and so we will try to treat anaemia or low iron stores early
  • drug and alcohol use.

If you have had a small baby before you have a higher chance of another unless you have changed something e.g. stopped smoking. We give some women a simple aspirin tablet each day from around 10 weeks of pregnancy until 36 weeks as studies have shown it helps the placenta supply the baby and encourage growth. You may be sent a prescription in the post. Booking late may mean you miss out on the chance to take this.

If we find that your baby is small, you will need to have more checks and scans. This is so that we can check that baby is:

  • growing: ask to see where the scanned weight of your baby plots on the grow chart (from the software)
  • in plenty of fluid
  • getting a good blood flow
  • coping well.

There may come a point when all is not well and it is time for your baby to be born. This would mean we would either induce (link) your labour or perform a caesarean. This can happen before your due date.

If your baby is less than 34 weeks we would try to give you steroids before baby is born. See Premature Labour and Birth.

This page was last updated at 4:35PM on August 18, 2021.