Growth of the baby

Many parents worry about the growth of the baby during pregnancy and are told they are having a small baby or growth of baby is slow. Read on for advice.

What is the normal growth of a baby in the womb?

Babies in the womb are called an embryo for the first 8 weeks, then they are called a fetus until they are born. Therefore you may hear your doctor or midwife talk about fetal growth.

During the first trimester, or 3 months, the growth of the baby is not visible – it is not until around 12 weeks of pregnancy that the uterus (womb) grows above the pubic bone. By now mum’s jeans are feeling pretty tight and it’s time to go up a clothes size! In just about all cases the fetal growth is uniform at this stage – the babies grow at the same rate and therefore a scan will tell you exactly how many weeks and days you have been pregnant.

The baby is still very small at this stage, but an enormous amount of your energy is zapped by the baby as it grows organs and limbs. By now baby is practically fully formed.

During the second trimester (12 – 28 weeks) the growth of babies will begin to differ and by the time that women have an 18 – 19 week abnormality scan the sizes of the babies will differ. Therefore a scan at this time is to look for abnormality, not to check dates from an irregular menstrual cycle. Many women think that a second scan changes their dates, but this is not the case. Only a scan up until 14 weeks gives absolutely reliable dates, after that it is an estimate.

By now, your midwife will be feeling your tummy (doing an abdominal palpation) when you have your regular pregnancy check. She will confirm that the size of your womb is in accordance with your dates, that you are feeling fetal movements (kicks) and she will usually listen to the heart beat too. Some midwives use a measuring tape, some use finger breadths, some use feeling alone to measure your baby’s growth. As babies do grow at differing rates and have growth spurts, your midwife will work within a normal range and be looking for steady growth and fetal kicks, as well as measuring your bump.

In the third trimester (28 – 40 weeks) fetal growth is variable – it changes from woman to woman, pregnancy to pregnancy. It is vital at this stage that the baby is kicking regularly and 10 separate kicks a day are considered a normal minimum. If a toddler is unwell they crash out on the sofa – if a baby is not getting a good blood supply the first thing they will do is slow down their movements to conserve energy. If a rest and a bite to eat do not get baby kicking in a couple of hours, it’s time to call your midwife. If ever in any doubt about movements, call immediately. Never go to sleep at night wondering if baby’s movements were OK that day. By the next day the baby might be sick and in trouble.

Your midwife or doctor will usually see you about every 2 weeks during this trimester and they will feel your bump each time to keep an eye on growth. By looking at a pregnant mum you cannot tell whether baby is a good size or not. Some women have wombs that stick out a lot, but carry small babies. The strength of your abdominal muscles, the number of children you have had, your height and the length of your abdomen will all affect how big you look! The only way to determine the size of the baby is to feel the baby or to have a scan. Both methods are variable, so it is great to have continuity at this time, so that the same professional feels the baby’s size each time.

When the midwife or doctor is talking about reduced growth of baby in the womb they may refer to it as Intra Uterine Growth Retardation, or IUGR.

What affects the baby’s growth in the womb?

Fetal growth, or the growth of baby, is affected by many factors, some of which are out of your control, for example:

• Pre eclampsia
• Twin or multiple pregnancies
• Hereditary factors (the size of the mum when she was a fetus)

Many factors are under our control when we are pregnant:

• Smoking will reduce the average size of babies, sometimes to dangerously low levels.
• Poor nutrition will affect baby’s growth.
• Alcohol can reduce growth and no one knows what the safe level of alcohol consumption is in pregnancy, so the general advice is to avoid alcohol in pregnancy.
• Excess exercise or dieting will affect baby’s nutrition too.

What can I do to ensure my baby grows well?

Here are some tips to ensure that your baby reaches their growth potential:

• Eat a well balanced diet
• Avoid smoking and smoky environments
• Avoid alcohol
• Rest each day, preferably in the afternoon for an hour, to ensure baby gets a good blood supply. If you are constantly rushing around, then your body will send less food and oxygen to the placenta. It can be difficult to rest if you have other children or a high pressured job. Speak to your whanau and friends to see what they can do to help you.

How will I know whether my baby is growing well?

Regular check ups with your midwife or doctor will usually confirm that the baby is growing well. Also they will check that you are feeling plenty of regular movements every day and explain what the local procedure is for reduced movements. Usually this involves going to the hospital to have the baby’s heart beat checked with a CTG machine.

If your health professionals suspect slowed growth they may organise a scan to check the size of the fetus. This is an estimate only, however.

What will happen if my baby does not grow normally?

If your maternity carers confirm that baby’s growth is slowed then a plan will be made with you and your team. The plan will vary enormously, depending upon how many weeks pregnant you are, how slow the growth is and whether there are other risk factors.

Options include:

• Regular scans
• Daily check or twice weekly checks
• Regular heartbeat checks (CTG)
• Induction of labour
• Caesarean section, in extreme cases only.

Remember babies will vary enormously in size and many babies are small because mum and dad are small and they are meant to be too.

Enjoy your pregnancy and don’t forget to count those kicks!

Useful articles

For more information on Pre-Eclampsia, click here

Read about Twin Births in our Kiwi Families article.