Intrauterine Growth Restriction (IUGR)/Small for Gestational Age (SGA)
A primary goal of an obstetric care provider is “the identification of pregnancies at risk for preventable perinatal morbidity and mortality.” 1 The same principal is a central tenant of the practice of midwifery. Both physicians and midwifes are taught to collect all data necessary for a complete evaluation of the woman, accurately identify problems or diagnoses based on a correct interpretation of the data, and to “anticipate other potential problems or diagnoses that might be expected because of the identified problems or diagnoses.” 2 One of the potential problems that these medical professional should consider is whether the baby may suffer from intrauterine growth restriction (IUGR), also sometimes referred to as small for gestational age (SGA). Generally “birth weight below the population 10 th percentile, corrected for gestational age, has been the most widely used criterion for defining growth restriction at birth.” 3
One reason it is important to consider whether a baby suffers from IUGR is because the perinatal mortality rate for IUGR babies is 6 to 10 times greater than for normally grown babies. 4 As many as 40 percent of all stillborns are growth restricted. 5 If the growth restricted baby is appropriately identified and managed, the perinatal mortality can be lowered. 6 It is critical therefore that the midwife or obstetrical care provider recognize those conditions which place a mother at risk for the development of an IUGR baby. Fortunately, these risk factors are well known.
A leading medical reference identifies the following risk factors for the development of an IUGR fetus: hypertension, renal disease, restrictive lung disease, diabetes, cyanotic heart disease, 7 Antiphospholipid Syndrome, 8 collagen-vascular disease, 9 hemoglobinopathies, 10 smoking, substance use and abuse, severe malnutrition, primary placental disease, multiple gestation, infections, genetic disorders, younger than 16 and older than 35, exposure to teratogens, 11 little maternal weight gain, low pre-pregnancy weight and low socioeconomic status. 12
These risk factors help to identify pregnant women who are at risk for the development of an IUGR fetus. Additionally, common and simple measures such as appropriate weight gain and fundal height are used to screen expectant mothers for suspected IUGR fetuses. Once a suspicion is raised, either through risk factors, inappropriate weight gain or inadequate fundal height, additional tests can be conducted that will help identify the growth restricted fetus. Unfortunately, the commonly used screening tests of inappropriate weight gain and fundal height are less reliable than other tests.
The use of fundal height is a commonly used method of determining the uterine size. Inferentially, if the uterus is increasing in size then presumably the baby is growing as well. The problem with this approach is that fundal height measurements are “prone to considerable inaccuracy and should be used for screening only, not as a sole guide to obstetric management in the presence of risk factors for or suspicions of IUGR.” 13 Clinical assessment of uterine size by fundal height “may be affected by distension of the bladder (up to 7 cm), maternal build, retroversion or retroflexion of the uterus, presence of fibroids, uterine anomaly, length of cervix, position and presentation of the fetus, location of the placenta, amniotic fluid volume, clinician experience, and missing or incorrect data concerning menstrual dates (as high as 43 percent).” 14
It is clear that when a woman has multiple risk factors that increase her risk of having an IUGR baby, the standard of care requires surveillance by ultrasonography. 15 This standard of care is summarized in the medical treatise Obstetrics Normal and Problem Pregnancies as follows:
Significant improvements have been made in detecting and characterizing the growth-restricted fetus. These improvements have served as the basis for plans designed to reduce the associated perinatal morbidity and mortality. Additional studies have confirmed the lack of sensitivity of fundal height measurements for detecting fetal growth restriction. The presence of risk factors should therefore prompt ultrasound estimation of fetal size independent of maternal weight gain or fundal height growth. [16]
Since growth restriction may occur at any time during the child’s development in the mother’s womb, it is necessary for the mother who is at risk to develop an IUGR baby to undergo an ultrasound at the 32-34 week time frame. Otherwise, there is a significant risk of failing to identify a baby who becomes growth restricted later in the pregnancy. Third trimester ultrasounds (approximately weeks 26 to 40) are very accurate. “A third trimester ultrasound examination, with a single measurement of abdominal circumference, detects about 80% of IUGR fetuses.” 17 Some medical providers also use arterial and venous Doppler studies to help identify the growth restricted fetus. 18
When ultrasound tests demonstrate the presence of an IUGR fetus, the caregiver has two options, depending on the age of the fetus. If the fetus is 36 weeks or younger, the caregiver does not attempt to induce delivery or perform a cesarean section as the baby’s lungs are not sufficiently developed at that point unless fetal well-being tests (AFI, NST, Biophysical profile, Doppler tests) indicate that the fetus is in distress. However, if an IUGR fetus is identified after 36 completed weeks, the fetus is near term, and the standard of care is to induce labor or arrange for delivery by a cesarean section. In other words, the caregiver does not wait for the baby to reach term since the incidence of delivering a still birth greatly increases once the IUGR baby reaches term.
“The majority of fetal deaths occur after the 36 th week of gestation and before labor which leads to the conclusion that many deaths could be prevented by accurate recognition of growth restriction and appropriately timed and conducted intervention.” 19 “Prompt delivery is likely for the fetus at or near term who is considered growth restricted.” 20
Each case is fact specific. If you or a loved one experiences a still born birth of a baby who is found to be growth restricted, it may be appropriate to have the relevant medical records reviewed to determine whether appropriate surveillance procedures were used.
References and Additional Readings
1. Norwitz E, Robinson JN, and Repke JT. Labor and Delivery. Chapter 13, Obstetrics Normal and Problem Pregnancies, edited by Gabbe S, Niebyl JR, Simpson JL. 4 th Ed. 2002.
2. Iams, JD. Preterm Birth. Chapter 23, Obstetrics Normal and Problem Pregnancies, edited by Gabbe S, Niebyl JR, Simpson JL. 4 th Ed. 2002.
3. Bernstein I, Gabbe SG, Reed KL. Intrauterine Growth Restriction, Chapter 25, Obstetrics Normal and Problem Pregnancies, Gabbe S, Niebyl JR, Simpson JL. 4 th Ed. 2002.
4. Fetal Growth Disorders, Chapter 12, High Risk Pregnancy Management Options, James DK, Steer PJ, Weiner CP, Gonik B. 3rd Ed. 2006, p. 250.
5. Chronic hypertension in pregnancy. ACOG Practice Bulletin, Clinical Management Guidelines for Obstetrician-Gynecologists, Number 29, July 2001.
6. Intrauterine growth restriction. ACOG Practice Bulletin, Clinical Management Guidelines for Obstetrician-Gynecologists, Number 12, January 2000.
7. Smoking cessation during pregnancy. ACOG Committee Opinion No. 316. American College of Obstetricians and Gynecologists. Obstet Gynecol 2005;106:883-8.
8. Ultrasonography in Pregnancy. ACOG Practice Bulletin, Clinical Management Guidelines for Obstetrician-Gynecologists, Number 58, December 2004.
9. Fetal Growth Disorders, Chapter 38, Williams Obstetrics, Cunningham FG, Leveno KJ, Bloom SL, Hauth JC, Gilstrap L, Wenstrom K. 22 nd Ed. 2005.
10. Basics of Management and Care, Chapter 2, Chapter 24, Varney’s Midwifery, Varney H, Kriebs JM, Gegor CL. 4 th Ed. 2004
11. Pharmacology and Midwifery, Chapter 10, Varney’s Midwifery, Varney H, Kriebs JM, Gegor CL. 4 th Ed. 2004.
12. Substance Abuse, Chapter 12, Varney’s Midwifery, Varney H, Kriebs JM, Gegor CL. 4 th Ed. 2004.
13. Screening for and Collaborative Management of Antepartal Complications, Chapter 24, Varney’s Midwifery, Varney H, Kriebs JM, Gegor CL. 4 th Ed. 2004.
14. Complications of Gestational Age Assessment and the Postdate Pregnancy, Chapter 25, Varney’s Midwifery, Varney H, Kriebs JM, Gegor CL. 4 th Ed. 2004.
15. T he Normal First Stage of Labor, Chapter 26, Varney’s Midwifery, Varney H, Kriebs JM, Gegor CL. 4 th Ed. 2004.
16. Engstrom JL, McFarlin BL, Sampson MB. Fundal height measurement part 4—accuracy of clinicians’ identification of the uterine fundus during pregnancy. Journal of Nurse-Midwifery 1993; 38, 6:318-323.
17. Alexander GR, Jimes JH, Kaufman RB, Mor J, and Kogan M. A United States national reference for fetal growth. Obstetrics & Gynecology 1996; 87, No. 2;163-168
18. AIUM Practice Guideline for the Performance of Obstetric Ultrasound Examinations. American Institute of Ultrasound in Medicine. 2007.
19. McFarlin BL. Intrauterine Growth Retardation: A review of etiology, diagnosis and management. 1994 Journal of Nurse Midwifery, 39,2: 52S -65S.
20. Fetal Growth Restriction, http://emedicine.medscape.com/article/261226-overview, Feb. 2011, Ross MG.
Footnotes:
[1] Bernstein at p. 869; and McFarlin BL. Intrauterine Growth Retardation: A review of etiology, diagnosis and management. 1994 Journal of Nurse Midwifery, 39,2: 52S -65S.
[2] Basics of Management and Care, Chapter 2, Varney’s Midwifery, Varney H, Kriebs JM, Gegor CL. 4 th Ed. 2004, p. 31.
[3] Bernstein I, Gabbe SG, Reed KL. Intrauterine growth restriction. Chapter 25, Obstetrics Normal and Problem Pregnancies, edited by Gabbe S, Niebyl JR, Simpson JL. 4 th Ed. 2002, p. 870.
[4] Bernstein at p. 869.
[5] Bernstien at p. 869.
[6] Bernstien at p. 869.
[7] Cyanotic heart disease is a heart defect that results in low blood oxygen levels.
[8] Antiphospholipid syndrome is a condition that can cause clotting within your arteries or veins and various other problems.
[9] Collagen is a tough, glue-like protein that represents 30% of body protein and shapes the structure of tendons, bones, and connective tissues. Malfunctioning of the immune system can affect these structures. This is known as collagen-vascular disease.
[10] Hemoglobinopathies are genetic (inherited) disorders of hemoglobin, the oxygen-carrying protein of the red blood cells.
[11] A teratogen is a substance that is capable of affecting the growth and/or development of the fetus. Under the Food and Drug Administration’s regulations, unless studies demonstrate that the drug in question is “not known to have a potential for indirect harm to the fetus,” the drug package insert must contain a statement setting forth a letter category.
[12] Intrauterine growth restriction. ACOG Practice Bulletin, Clinical Management Guidelines for Obstetrician-Gynecologists, Number 12, January 2000, p. 592.
[13] Engstrom JL, McFarlin BL, Sampson MB. Fundal height measurement part 4—accuracy of clinicians’ identification of the uterine fundus during pregnancy. Journal of Nurse-Midwifery 1993; 38, 6:318-323, p. 318; Intrauterine growth restriction. ACOG Practice Bulletin, Clinical Management Guidelines for Obstetrician-Gynecologists, Number 12, January 2000, p. 594.
[14] Wood CL. Complications of Gestational Age Assessment and the Postdate Pregnancy, Chapter 25, Varney’s Midwifery, Varney H, Kriebs JM, Gegor CL. 4 th Ed. 2004, pp. 718-719; McFarlin BL. Intrauterine Growth Retardation: A review of etiology, diagnosis and management. 1994 Journal of Nurse Midwifery, 39,2: 52S -65S; and Engstrom JL, Work BA Jr., Prenatal prediction of small- and large-for-gestational age neonates. Journal of Obstet. Gynecol. Neonatal Nursing., 1992 Nov-Dec;21(6): 486-95.
[15] Intrauterine growth restriction. ACOG Practice Bulletin, Clinical Management Guidelines for Obstetrician-Gynecologists, Number 12, January 2000, p. 595.
[16] Bernstein at p. 874.
[17] Intrauterine growth restriction. ACOG Practice Bulletin, Clinical Management Guidelines for Obstetrician-Gynecologists, Number 12, January 2000, p. 595.
[18] Baschat AA. Fetal Growth Disorders, Chapter 12, High Risk Pregnancy Management Options, James DK, Steer PJ, Weiner CP, Gonik B. 3rd Ed. 2006, p. 250.
[19]Bernstein at p. 883.
[20] Fetal Growth Disorders, Chapter 38, Williams Obstetrics, Cunningham FG, Leveno KJ, Bloom SL, Hauth JC, Gilstrap L, Wenstrom K. 22 nd Ed. 2005, p. 903.