As doulas, we are non-medical prenatal, birth, and postpartum support. However, it is important that we are familiar with medical and clinical terms and management. Understanding Intrauterine Growth Restriction (IUGR) and Small For Gestational Age (SGA) is an important way we can best support our clients.
Both are complications of pregnancy which can occur for a variety of reasons. We cannot advise our clients on how they should handle clinical complication. We can provide them with evidenced based information, guidance on discussing options with their providers, and support them as they manage any pregnancy complications.
While both terms sound similar, they have different diagnostic criteria and can occur for different reasons.
Knowing about the potential for IUGR, SGA, and other things also helps us in encouraging clients to maintain regular prenatal care. We know that prenatal care can reduce the risk of complications, as well as improve outcomes when complications do arise.
What Are IUGR And SGA?
Intrauterine growth restriction is most often defined as a fetal weight of less than the 10th percentile for gestational age. It is also described sometimes referred to as fetal growth restriction.
Small For Gestational Age (SGA) is used after a baby is born and it is determined they are under the 10th percentile for the gestation they are born at. A baby can be IUGR and then SGA, but they can also have no prior IUGR diagnosis and then be SGA.
IUGR – describes a fetus which has not reached its expected growth potential because of genetic or environmental factors
SGA – describes a baby whose birth weight is below the 10th percentile for their gestational age
Fetal weight is an estimate, based on ultrasound measurements. Providers measure the fetal weight and size during the routine anatomy scan. Most maternity care providers do not refer for or perform routine growth scans in low-risk pregnancies.
However, measuring fundal height (the size of the uterus) is part of routine prenatal appointments. If the fundal height isn’t growing as expected, one’s midwife or doctor might refer for an ultrasound to estimate fetal size.
What Is The Difference Between Primary and Secondary IUGR?
Understanding clinical terms is an important part of being an adequate support to your clients. If a client or potential client discusses their prenatal appointments and concerns, it’s important you understand what they are sharing with you. It’s also important to be able to help them understand more about what they might experience.
There are two types of IUGR. One is primary, or symmetric, IUGR. This is when the baby is proportionally small for gestational age. The head, brain, abdomen, and internal organs are all measuring similarly, and are smaller than the 10th percentile.
Secondary, or asymmetrical, IUGR is when the baby’s head and brain are measuring on target, but the abdomen is small for gestational age. Typically, provider’s don’t see secondary IUGR until the third trimester.
Primary IUGR accounts for about 25% of IUGR cases. It’s also important to note that if a baby is small at birth, it isn’t necessarily IUGR. Only one in three babies who are small at birth are smaller due to IUGR.
What Are The Risk Factors For IUGR?
While there isn’t always a clear answer for why a baby develops IUGR, there are some risk factors and known causes. As a birth professional, knowing risk factors can help you best support your clients. While we are not going to tell mothers they have risk factors for x, y, z conditions and create fear, we can support any questions they have about what they may read or hear.
Some risk factors include:
- An underweight mother
- A multiples pregnancy
- Chromosomal abnormalities or birth defects
- Umbilical or placental abnormalities
- Gestational diabetes
- Pregnancy induced hypertension
- Poor maternal nutrition
- Maternal use of drugs, alcohol, or cigarettes
- Polyhydramnios or oligohydramnios
It’s important to note that having a risk factor does not mean a baby will experience IUGR. It’s also important to note that IUGR can occur even when there’s no known risk factor.
If a small fundal height is of concern, and/or there are certain risk factors (e.g. umbilical or placental abnormalities, multiples pregnancy, or gestational diabetes) a midwife or doctor might refer a client for regular ultrasounds until there’s a diagnosis, or until any concerns are ruled out.
How Is IUGR Diagnosed?
During routine ultrasounds, or ones referred for growth scans, consist of an ultrasound tech or doctor taking different measurements of the baby. If a baby appears to be smaller than the 10th percentile overall, or baby’s abdomen is measuring small for gestational age, while the head is not, there might be diagnosis of IUGR or possible IUGR.
Monitoring for IUGR does not necessarily mean a diagnosis. Many providers prefer to have at least two or three growth scans done to determine a baby’s growth pattern. Sometimes babies are simply smaller than average but continue to grow well on their own growth curve.
Some babies tend to grow in spurts. If a scan is done just before a spurt, these babies might appear small. However, by the next scan they will be back on track. It is also possible that the ultrasound size estimates in one scan were slightly inconsistent, due to differences in machines, or in the ultrasound technician’s experience level.
One of the most important things to keep in mind when secondary IUGR is suspected is accurate gestational age. Estimated due dates and gestational age are only estimates, which can vary by up to two weeks. Variations in dating is why it usually requires multiple scans to confirm an IUGR diagnosis.
How Is IUGR Treated?
Mostly, an IUGR diagnosis simply means extra monitoring. Your client may remain under the care of their regular midwife or doctor, while receiving consultative care by a maternal fetal medicine specialist. In some cases, they may only receive ultrasounds at a regular clinic and the reports monitored by their midwife/OB.
Occasionally, an IUGR diagnosis will mean a full transfer of care to a high-risk OB, or maternal fetal medicine specialist.
A doctor or midwife maintaining your care or transferring depends on the stage of pregnancy and possible cause of IUGR. For example, if doctors suspect a genetic condition, they may transfer care to a faciality able to manage the baby’s newborn care.
IUGR Treatment Is Based On Gestation
For clients under 34 weeks, treatment is typically monitoring with the goal of reaching a full-term pregnancy. Most providers will continue to monitor fetal growth, placental function, and umbilical cord function. If there’s concern baby is not receiving adequate flow via the placenta or umbilical cord, they may opt for an early, premature, delivery.
If your client is over 34 weeks, the same monitoring occurs. However, they may be more likely to consider preterm delivery during the 34-37 week range as the benefit risk analysis is now different with a more mature (albeit still premature) baby.
Determining monitoring versus early birth comes down to assessing whether baby is more at risk for complications in utero than in the NICU. As a doula, you can help your client feel confident in discussing options with their provider. Remind them to ask specific questions about benefit versus risk. Then simply support them in whichever decisions they and their providers land on.
As a doula, the most important thing is to support your client. Help your client understand their options. Encourage them to have regular discussion with their provider. And ultimately, hold space for their birth, however it needs to unfold.