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Selective Intrauterine Growth Restriction (sIUGR)

Selective intrauterine growth restriction (sIUGR) is a fetal condition that can affect identical twins who share a single placenta inside the womb, also referred to as monochorionic twins.

Selective growth restriction occurs when the babies don’t share the placenta equally, leading one twin to experience growth problems.

Selective Intrauterine Growth Restriction: Why Choose Us?

As the only full-service fetal care center in the St. Louis region, we offer exceptional care for women whose unborn babies face complex challenges. You’ll be cared for by experienced doctors from three highly respected medical institutions: Barnes-Jewish Hospital, St. Louis Children’s Hospital and Washington University Physicians.

We diagnose this condition using specialized ultrasound and other diagnostic technologies, only available at select centers nationwide. Our doctors have extensive experience treating this rare condition. This allows our doctors to distinguish between sIUGR and similar fetal conditions that affect monochorionic twin pregnancies, like twin-to-twin transfusion syndrome.

Our fetal care specialist team works together to monitor mothers and babies affected by sIUGR throughout their pregnancy. We tailor treatments to the special needs that make every family unique.

What Is Selective Intrauterine Growth Restriction?

In most monochorionic pregnancies (where identical twins share one placenta), each twin receives a similar percentage of nutrients from the placenta they share. In cases of sIUGR, the placenta is not shared equally, resulting in one twin receiving more nourishment from the placenta than the other twin. This results in one twin becoming significantly smaller than the other twin.

sIUGR can sometimes lead to significant problems for the baby during pregnancy or after birth. Severe cases can be life-threatening for one or both babies.

When sIUGR happens early in pregnancy, it may cause more serious issues than when the condition occurs later in pregnancy. In general, sIUGR prognosis improves when the condition occurs later in pregnancy.

Selective Intrauterine Growth Restriction Cause

In sIUGR, unequal sharing of the placenta causes twin unborn babies to grow at different rates inside the womb. sIUGR affects about 1 in 10 identical twin pregnancies. The condition happens at random, with no obvious contributing causes.

Diagnosing Selective Intrauterine Growth Restriction

Our sonographers use advanced diagnostic ultrasound equipment to diagnose sIUGR. A diagnosis may be made when one or more factors are present, including:

  • A more than 25% difference in the estimated fetal weight of both babies
  • One baby’s estimated fetal weight less than the 10th percentile compared to unborn babies of a similar age
  • One baby’s abdominal circumference measurement less than the 10th percentile compared to unborn babies of a similar age
  • A decrease in the amount of amniotic fluid surrounding the smaller baby
  • Abnormal blood flow patterns in the umbilical cord

Our fetal care specialists are highly experienced, performing more than 5,000 fetal evaluations every year. At the Fetal Care Center, one of our specialists reviews all test results with you and explains what they mean. We walk you through the basics of any health condition that affects you or your unborn babies, at the time of diagnosis. Our goal is to inform you so you feel confident in your care.  We are partners in your care.  

Learn more about high-risk pregnancy tests.

Treating Selective Intrauterine Growth Restriction

We personalize sIUGR care to match your unique situation. Our doctors closely monitor both of your unborn babies’ growth and development regularly throughout your pregnancy. The Fetal Care Center partners with your doctor so women who live farther away from St. Louis may be able to get some of their testing done closer to home, while still receiving optimal care. 

Our doctors may recommend you undergo twice-weekly (or more frequent) specialized fetal testing to evaluate the health of the babies. These tests may include:

  • Doppler studies to monitor the flow in your baby’s umbilical cord, liver and brain
  • Biophysical profiles may use ultrasound and/or fetal heart tests to check on your baby’s well-being, including breathing, movement and amniotic fluid levels
  • Non-stress tests (NSTs) measure your baby’s heart rate

Our goal in treating sIUGR is to prolong the pregnancy for as long as possible for both unborn babies. In severe cases, sIUGR may threaten the life of one or both babies. 

If necessary, our specialists will guide you through available treatment options. We work with our pediatric advanced care team, newborn medicine team and perinatal behavioral health service care team to help families navigate even the most difficult situations, both during pregnancy and after delivery.

Preterm delivery is common. At the Women & Infants Center, many specialists work together to deliver the best outcomes for mothers and babies at high risk of complications. Our team of fetal care specialists carefully plan the timing of your delivery. And a team of newborn and pediatric specialists stands ready to tend to both babies immediately after delivery. 

Newborns affected by sIUGR receive specialized care in the Women & Infants Center’s level IV newborn intensive care unit (NICU) at St. Louis Children’s Hospital. Our NICU is near the delivery room, to keep moms and babies closely connected.

Contact Us

To make an appointment with a Washington University fetal care specialist at the Women & Infants Center, call 855.925.0631.