There are various reasons why a baby may stop growing in the womb, a condition known as intrauterine growth restriction (IUGR) or intrauterine growth retardation (IUGR). Some common causes include problems with the placenta, birth defects, infections, chronic health conditions in the mother, and substance abuse. IUGR is a serious concern, as it can lead to stillbirth and many health issues for the baby after birth if not managed properly. Detecting IUGR early and determining the cause is critical for the best outcome.
What is IUGR?
IUGR refers to poor growth of the baby while in the mother’s womb during pregnancy. The baby has a birth weight below the 10th percentile for gestational age, meaning it is smaller than 90 percent of fetuses of the same gestational age. IUGR has various causes, some related to the baby and others related to the mother’s health or placenta function. IUGR increases the risk of perinatal mortality and morbidity as well as the development of adult onset diseases later in life.
Key Facts and Statistics
- IUGR complicates up to 10 percent of pregnancies.
- Up to 70 percent of stillbirths are associated with IUGR.
- IUGR increases the risk of perinatal mortality up to 10 times.
- Babies with IUGR are at increased risk of impaired neurodevelopment.
- IUGR is linked to a higher risk of developing diabetes, obesity, hypertension, and heart disease as an adult.
Common Causes of IUGR
Placental Insufficiency
One of the most common causes of IUGR is placental insufficiency. The placenta is vital for providing oxygen and nutrients to the developing baby from the mother’s blood supply. Placental insufficiency occurs when the placenta is abnormal or fails to develop optimally, restricting blood flow and nutrient transport. This limits the supply of oxygen and nutrients to the fetus, restricting growth.
Causes of placental insufficiency include:
- Placental abnormalities like placenta previa
- Maternal blood vessel damage
- Maternal chronic hypertension
- Autoimmune disorders like systemic lupus erythematosus
Pregnancy-induced Hypertension
High blood pressure disorders in pregnancy like preeclampsia and eclampsia can impair blood flow across the placenta. This disrupts oxygen and nutrient delivery to the fetus and causes IUGR. Preeclampsia, related to abnormal function of the placenta, is a leading cause, complicating 5-10% of pregnancies.
Congenital Infections
Maternal infections during pregnancy like cytomegalovirus, toxoplasmosis, rubella, and syphilis can cross the placenta and cause fetal infection. This often damages the placenta and umbilical cord, reducing blood flow and oxygen delivery to the fetus and resulting in IUGR.
Chromosomal and Genetic Defects
Fetal chromosomal abnormalities like trisomy 13, 18 and 21 and genetic disorders like congenital heart defects put pregnancies at higher risk for IUGR. These conditions physically limit growth potential.
Multiple Pregnancy
In twin, triplet or higher multiple pregnancies, competition for nutrients between fetuses may result in IUGR of one or more babies. The placentas share space in the uterus, receiving uneven blood flow distribution.
Maternal Risk Factors
Several maternal factors raise the risk of IUGR:
- Smoking, alcohol or illicit drug use
- Chronic conditions like kidney disease, hypertension, and heart disease
- Autoimmune diseases
- Uterine abnormalities or small uterus
- Low pre-pregnancy weight, poor weight gain, undernutrition
- Teenage pregnancy
- Pregnancies spaced less than 2 years apart
- Previous history of miscarriage or IUGR
Diagnosing IUGR
IUGR is diagnosed through:
- Tracking fundal height and fetal growth progress
- 3D and 4D ultrasonography to visualize fetal anatomy and measure size
- Doppler ultrasounds to examine umbilical arterial blood flow
- Fetal movement monitoring
- Amniotic fluid volume assessment
- Biophysical profile combining fetal heart rate, movement, breathing and fluid volume
IUGR is suspected if there is a flattening of the normally exponential fetal growth curve or a fetus is found measuring small for gestational age. Further testing helps confirm the diagnosis and determine the potential cause like placental dysfunction or congenital abnormalities.
Risks and Complications
IUGR leads to risks and complications, including:
- Stillbirth
- Neonatal mortality
- Birth trauma during labor and delivery
- Hypoglycemia, polycythemia, hypothermia, feeding difficulties
- Respiratory distress syndrome
- Neurodevelopmental impairment – cognitive deficits, cerebral palsy
- Impaired immunity and increased infections
- Hearing and vision problems
- Childhood obesity and metabolic syndrome
- Adult onset cardiovascular disease, diabetes
The earlier the IUGR occurs in pregnancy and the more severe, the higher the risks of complications. Stillbirth risk is 10 times higher with IUGR. Improved neonatal care has increased survival of IUGR infants but they remain prone to morbidities.
Management and Treatment
When IUGR is diagnosed, management focuses on monitoring the fetus and optimizing growth while balancing the risks of prolonged pregnancy.
- Increased prenatal visits to monitor fetal wellbeing – nonstress tests, biophysical profiles
- Ultrasound monitoring of growth, amniotic fluid levels and umbilical artery blood flow
- Search for and treatment of any underlying maternal cause if found like infection
- Modify activity if preeclampsia or hypertension present
- Medications like corticosteroids to mature the fetal lungs if early delivery anticipated
- Early delivery if the risk of stillbirth from staying in utero outweighs risks of prematurity
After birth, IUGR infants need special neonatal intensive care with meticulous management of breathing, nutrition, temperature, blood sugar, and infection risk. Neurodevelopmental follow-up care monitors any impairments.
Prevention
Some recommendations to help prevent IUGR:
- Achieve normal BMI before pregnancy
- Gain adequate weight during pregnancy
- Take folic acid supplements
- Control pre-existing maternal health conditions
- Avoid smoking, alcohol and illicit drugs
- Treat infections and STDs prior to pregnancy
- Space pregnancies at least 2 years apart
- Get early and regular prenatal care
Prenatal screening and diagnosing IUGR early allows for optimal management to limit complications. However, some causes like genetics and chronic maternal health issues are not preventable.
Conclusion
IUGR or failure of the baby to reach its growth potential in the womb is a concerning pregnancy complication. It has varied causes, some fetal and others maternal or placental in origin. IUGR increases the risks for perinatal mortality and long-term morbidities. Thorough evaluation to determine the etiology, close monitoring of fetal growth and wellbeing, and timely delivery when indicated offer the best outcomes. Preventing contributing factors through optimal pre-pregnancy health and prenatal care is important. While not all IUGR can be avoided, excellent management improves the prognosis.