Fetal Growth Restriction

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Fetal Growth Restriction

Fetal Growth Restriction (Small Baby)

When your baby was measured, we believe the baby is too small. This is called fetal growth restriction (FGR). This happens in about 10% of pregnancies.

graphic showing percent of pregnancies affected by fetal growth restriction

What is it?

  • When your unborn baby is smaller than they should be or isn’t growing at the normal rate.
  • Fetal growth Restriction is when the baby’s weight is less than 10th percentile of the usual weight at that gestational age. That means that out of 10 babies, your baby weighs less than 9 of them who are the same gestational age. A baby also has fetal growth restriction if the size of their belly is less than the 10th percentile for that gestational age even if their total weight is normal.
  • During your prenatal visit if your belly measures smaller than expected in the office they may recommend an ultrasound to see if the baby’s size is normal.
  • It is hard to tell the difference between a small but healthy baby and a baby that is not growing normally and has more risks. Some babies who are small when measured by an ultrasound may be normal size when they are born.
  • Some babies will show other signs that they have fetal growth restriction like less water (amniotic fluid) around the baby, abnormal circulation (doppler measurements), or problems with the placenta.
  • About 20% of babies (2 out of 10) who seem to have fetal growth restriction on ultrasound are small, but healthy and won’t have any complications when they are born.

What causes it?

  • Problems with the placenta or umbilical cord are the most common causes. Having health problems like diabetes and high blood pressure or using drugs, tobacco, or alcohol in the pregnancy can cause fetal growth restriction.
  • Genetic diseases in the baby.
  • Infections that can make the baby too small.
  • If you had a baby with fetal growth restriction in the past, there is a higher chance it can happen in another pregnancy.

**SENSITIVE TOPIC ALERT, this next section talks about serious risks to babies**

What can happen if my baby has fetal growth restriction?

  • A baby with fetal growth restriction has a higher chance of stillbirth than normal weight babies. The risk is worse if the baby’s weight is very low or if there are signs the placenta is not working well.
     
    Risk of Stillbirth for Pregnancies with no Fetal Growth Restriction and Pregnancies with Fetal Growth Restriction
    Pregnancies with no Fetal Growth Restriction 6.4/1000   (0.64%)
    Fetal Growth Restriction less than 10th percentile 12/1000     (1.2%)
    Fetal Growth Restriction less than 5th percentile 25/1000     (2.5%)
    Fetal Growth Restriction less than 3rd percentile 50/1000     (5.0%)
  • If you have other health problems in your pregnancy like high blood pressure or diabetes the risks may be higher.
  • There is more chance that a baby may be stressed during labor. Some studies show that pregnancies with fetal growth restriction have more c-sections (cesarean birth). The risk of stress and c-section may be higher the longer you are pregnant.
  • There is more chance that the baby will need to go to the neonatal intensive care unit after they are born. Babies with fetal growth restriction can have problems with low blood sugar, high bilirubin (jaundice), infections, or trouble breathing after birth.

What can be done about it?

  • We recommend more frequent monitoring of the baby using ultrasound to check the baby’s weight, the circulation of blood (dopplers), how much fluid is in the bag of water (amniotic fluid), and the baby’s heart rate.
  • We recommend visits in the ultrasound unit one or two times a week.
  • We may recommend a visit with a high-risk obstetrician (maternal-fetal medicine doctor) and a genetic counselor if the baby is too small or if you have other health problems
  • Most babies with fetal growth restriction will grow more outside in your arms than inside the belly (uterus). Sometimes babies will grow more during the pregnancy.
  • Some babies who are measured small will have a normal weight or belly measurement later in the pregnancy. If this happens you will continue to have normal prenatal care.
  • If the baby continues to grow less than normal, we recommend starting your labor at the hospital before your due date. Your provider or a high-risk obstetrician will talk to you more about when the right time is for you and your baby.
     
    When Should my baby be born? Week of pregnancy
    Baby is smaller than the 10th percentile and bigger than 3rd percentile 38-39 weeks pregnancy
    Baby’s abdomen is smaller than the 10th percentile 38-39 weeks pregnancy
    Baby is smaller than the 3rd percentile 37 weeks
    Other concerns seen on ultrasound Possibly before 37 weeks, Talk to your provider for more information

References

  1. Management of Stillbirth, Obstetrics & Gynecology: March 2020 - Volume 135 - Issue 3 - p e110-e132
    doi: 10.1097/AOG.0000000000003719

  2. Fetal Growth Restriction, Obstetrics & Gynecology: February 2021 - Volume 137 - Issue 2 - p e16-e28
    doi: 10.1097/AOG.0000000000004251

  3. https://www.highriskpregnancyinfo.org/fetal-growth-restriction-fg