Having a small for gestational age (SGA) baby

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What does the leaflet cover?

  • Possible reasons why your unborn baby may be small
  • How to reduce the risk of your baby not growing well
  • How the diagnosis of a small unborn baby can be made
  • What extra care to expect if you are thought to be having a small baby.

What is meant by a small baby during pregnancy?

Babies are sometimes called small for gestational age (SGA) or small for dates (SFD). Almost 90% babies that are smaller than expected will be healthy.

What affects my baby’s birthweight?

Your baby’s weight is affected by many things, including:

  • Your height and weight – taller, heavier women tend to have heavier babies.
  • Whether you or your partner were a small baby.
  • Your ethnicity – for example, South Asian women tend to have smaller babies.
  • The number of babies you have had – babies tend to become heavier with each pregnancy.
  • Whether your baby is a boy or a girl – boys tend to be heavier.

What could cause my baby to be small?

Your baby could be small because of a combination of the factors above. If this is the case, your baby is likely to be healthy because he or she is meant to be small. However, sometimes babies are small because they do not grow as well as expected. This is called fetal growth restriction (FGR).

Causes of fetal growth restriction include:

  • The placenta not working as well as it should – this could be because of medical problems such as high blood pressure or complications of pregnancy such as pre-eclampsia, smoking, using drugs or being very anaemic can also affect how your placenta works.
  • An infection during pregnancy that affects the baby such as cytomegalovirus or toxoplasmosis.
  • Having a baby with a developmental, chromosomal or genetic problem.

However, we don’t always know why FGR happens. Up to 10% of pregnancies will be affected by FGR and will need close monitoring during
pregnancy. In some cases, you may need to give birth earlier than expected.

Is there anything that increases the risk of FGR?

There are several things that can increase the risk of FGR. The most common risks are:

  • If you have previously had a small baby, pre-eclampsia or stillbirth.
  • If you have had complications earlier in this pregnancy, particularly heavy bleeding.
  • Having a pre-existing medical problem such as high blood pressure, kidney problems, diabetes or heart disease.
  • Smoking, drinking alcohol or using illegal or recreational drugs
  • Being over 40 years of age.

If you have any bleeding during your pregnancy, with or without pain, it’s very important to get it checked out.

Can I do anything to reduce the risk?

Some things that increase your risk of having a small baby can’t be changed. But there are some things you can do to reduce the risk, including:

  • Stopping smoking.
  • Taking vitamin D.
  • Eating a healthy, balanced diet.
  • Not drinking alcohol.
  • Not using illegal/recreational drugs, especially cocaine.
  • maintain a healthy weight before and during pregnancy.
  • If you are overweight, you are more likely to develop high blood pressure, which can cause complications leading to problems with the baby’s growth.
  • High levels of caffeine in pregnancy has been linked to low birthweight, as well as miscarriage. Try to limit your caffeine to 200 milligrams (mg) a day. This is about the same as 2 mugs of instant coffee.
  • If you are at increased risk of pre-eclampsia, you may be advised to take low dose aspirin (150 mg once a day) from 12 weeks of pregnancy until your baby is born.

What does FGR mean for my baby?

If your baby is small but healthy, he or she is not at increased risk of complications. If your baby is growth restricted, there is an increased risk of stillbirth (the baby dying in the womb), serious illness and dying shortly after birth. The earlier in pregnancy and the more severely your baby’s growth is affected, the more likely it is that your baby will have a poor outcome. Babies whose growth is only affected later in pregnancy have a better outcome.

Most babies affected by infection or by developmental or genetic problems have severe growth restriction and are usually detected early.

Once your healthcare team has identified that your baby is small, you will be offered extra monitoring in SGA clinics to keep an eye on your baby’s growth and wellbeing. You are likely to be advised to have your baby early to be as certain as possible that your baby will be born healthy. These clinics are run by fetal medicine specialists on either Mondays, Tuesdays, or Thursdays.

How will I know if I am having a small baby?

If you have no risk factors for FGR identified in early pregnancy, your midwife will start to measure your bump from 26-28 weeks, during your routine antenatal appointments, to check that your baby is growing well. This is a simple test using a tape measure. They will measure your bump from the top of the uterus (womb) to your pubic bone. The measurement should then be plotted on a growth chart in your personal maternity record.

If your midwife has any concerns about the baby’s growth from this measurement, you will be referred for an ultrasound scan within 72 hours. This does not necessarily mean something is wrong. The scan is just a more accurate way of assessing the baby’s growth.

If you have any risk factors for FGR, the growth of your baby will be monitored by ultrasound scans instead of using a tape measure.

Depending on your medical and pregnancy history, you may also be referred for an ultrasound scan to measure the blood flow to your placenta (this is known as the uterine artery Doppler). This measurement is done at 20–24 weeks of pregnancy. It will determine how often you will need to have ultrasound scans during your pregnancy.

If my baby is small or not growing, what other tests may I be offered?

You may have the following tests to check your baby’s wellbeing:

  • Umbilical artery Doppler – this measures the flow of blood through the umbilical cord.
  • A cardiotocograph (CTG) – this is a tracing of your baby’s heart rate.
  • Measuring the amount of amniotic fluid around your baby.

If your baby is identified to be below the 10th centile and you are still less than 36 weeks,you will be offered 2 weekly scans to check baby’s growth in ultrasound department. You will be referred to a fetal medicine specialist in SGA clinic for more frequent and detailed scans if:

  • Your baby is below the 3rd centile at any time in pregnancy.
  • If you are 36 weeks and your baby is below the 10th centile.
  • The umbilical artery Doppler test is abnormal or the fluid around your baby has reduced.

You will also be referred to antenatal day assessment unit (ADAU) for a CTG following your scan.

Monitoring your baby’s movements

It’s very important to monitor your baby’s movements during pregnancy. Most women usually begin to feel their baby move between 16 and 24 weeks of pregnancy. A baby’s movement can be described as anything from a kick, flutter, swish or roll. There is no set number of normal movements. If you think that your baby’s movements have slowed down or stopped, it is important that you contact your midwife or ADAU immediately. Do not wait until the next day to seek advice. This is particularly important if there are concerns about your baby’s growth during pregnancy.

Will FGR affect how I give birth?

Most women who want one will be able to try for a vaginal birth, if there are no other complications. Your baby will be monitored closely during labour. It is likely that you will be advised to give birth early. This may just be a week earlier than your expected date of delivery (39 weeks) or it may be several weeks before(37 weeks or earlier), depending on how your baby is.

Some babies may be too small to go through labour and a vaginal delivery, so you may be advised to have a caesarean section. Fetal medicine specialists will talk to you about what they think is best. Your baby may need to go to neonatal unit (NNU) following birth .This is because your baby may need extra care, especially if they are very small and born early (prematurely). Not all small babies will need to go to NNU.

Depending on when and how you are going to have your baby, you may be offered steroids to help your baby’s lung development and reduce the chance of breathing problems after birth. You may also be offered magnesium sulphate, which is a medicine given before delivery to reduce the risk of cerebral palsy.

Will FGR affect my next pregnancy?

If you get pregnant again, the risk of having a small baby again is slightly higher. But you may be able to reduce your risk by trying to live a healthy lifestyle. It can help to:

  • Not smoke.
  • Eat a healthy, balanced diet.
  • Not drink alcohol.
  • Not use illegal drugs or recreational drugs, especially cocaine.
  • Work with your healthcare professional to make sure any long-term conditions, such as diabetes, are managed well.

In your next pregnancy, your doctor may recommend that you take low-dose aspirin (150mg) at night from 12 weeks of pregnancy.

Try not to worry too much if you want to get pregnant again. Your care will likely depend on what risk factors you have, but if you’ve had a small baby before, your healthcare team will monitor you closely during your next pregnancy.

What should I do if I have concerns or further questions?

  • Talk to your community midwife
  • Call ADAU on 01908 996 483
  • Call the Fetal Medicine Specialist Midwife on 01908 995 236
  • Speak to your consultant at your antenatal clinic appointment