Intrauterine growth restriction, also known as IUGR, is a medical term utilized for poor growth in utero. This occurs when the baby is not growing to the expected size that it should at its gestational age. IUGR is very common and is caused by a variety of reasons.
The two types of IUGR include symmetrical and asymmetrical. Symmetrical IUGR means that all parts of the baby’s body and head are small and all body parts are within the same growth percentiles. Asymmetrical IUGR occurs when the baby’s head and brain are their expected size for gestational age, but the body is smaller. Asymmetrical IUGR is also often termed head sparing IUGR. Both forms of IUGR lead to slowed growth in utero and can lead to low birth weight once they have reached full term.
Most often, IUGR occurs if a baby is not getting enough nutrients while in utero. This typically is due to two main reasons: placental issues or umbilical cord issues. It is important to note that most causes of IUGR have nothing to do with the mother’s diet or nutritional status.
Other very common causes of IUGR include:
During pregnancy, the baby’s growth will be measured in two main ways: fundal height and via ultrasound. Typically, physicians measure a woman’s fundal height or uterine height at each visit. Fundal height is the measurement between the top of the pubic bone to the top of the uterus. This measurement is compared to the gestational weeks and if the measurement is less than expected, then the mother may be screened further for IUGR.
A prenatal ultrasound is the gold standard for diagnosis of IUGR. An ultrasound can take direct measurements of the baby’s body and head in order to determine if they are growing slower than expected.
Once IUGR has been diagnosed, then treatment typically involves serial monitoring. As long as the baby continues to grow, even if at a slowed rate, then the baby is safe in utero. Sometimes doctors will do weekly to biweekly ultrasounds to determine growth and ensure that the baby is thriving. Sometimes, induction of labor at an earlier date is also recommended if the baby stops growing. Most babies with IUGR do well once born and have catch up growth outside of the womb.