|Year : 2017 | Volume
| Issue : 4 | Page : 267-270
Diagnosis of intrauterine growth restriction
Anne George Cherian
Associate Professor (Obstetrics and Gynecology), Department of Community Health, Christian Medical College, Vellore, Tamil Nadu, India
|Date of Web Publication||17-Nov-2017|
Anne George Cherian
Department of Community Health, Christian Medical College, Vellore - 632 004, Tamil Nadu
Source of Support: None, Conflict of Interest: None
Fetal growth restriction is an adverse event in pregnancy, and the goal of antenatal monitoring is early detection of intrauterine growth restriction (IUGR). This involves the correct determination of gestational age to differentiate fetal growth restriction from a perceived restriction due to the wrong estimation of the gestational age. The use of ultrasound studies to estimate fetal size, growth, and volume of liquor along with simple charting of fetal growth can help diagnose IUGR and guide the physician toward remedial measures. This review discusses clinical examination as well as investigations needed to confirm the diagnosis of fetal growth restriction.
Keywords: Gestational age, intrauterine growth restriction, symphysiofundal height
|How to cite this article:|
Cherian AG. Diagnosis of intrauterine growth restriction. Curr Med Issues 2017;15:267-70
| Introduction|| |
The goal of antenatal monitoring is early detection of intrauterine growth restriction (IUGR) so that antenatal management can be optimized for better neonatal outcome. Unfortunately, in spite of these initiatives, the overall outcome of IUGR has not changed much over time. Close monitoring will lead to changes in the time of delivery or management, but despite this, there is still some controversy over the appropriate type and timing of antenatal monitoring.
A 22-year-old woman. (gravida 1) presents to the physician who has been providing her prenatal care. Her past medical history was not significant. At the 32-week visit, her blood pressure was 140/95 mm. Hg and she had gained 2.25 kg. (5 lb) since her last visit. Urine dipstick testing showed 2+ . protein. Fundal height was 28 cm, unchanged from the measurement obtained at the 30-week visit. The physician suspects growth restriction secondary to the onset of preeclampsia. What will be the next step in management?
The case is discussed at the end of the article.
| Calculating Gestational Age|| |
To diagnose IUGR, it is very important to be sure of the gestational age. The use of last menstrual period (LMP) to calculate the gestational age is a simple method and is the most widely practiced. However, the LMP can sometimes be unreliable. In this setting, a first-trimester ultrasound is the most reliable tool to calculate gestational age. Early ultrasound examination, ideally at eight to 13 weeks of gestation, is more accurate for estimating gestational age than ultrasound assessment later in pregnancy.
An ultrasound examination performed no later than the 20th gestational week when the margin of error is seven to 10 days is the next reliable option. Although ultrasound assessment is used later in pregnancy to estimate fetal weight, ultrasound dating is only accurate to about 3 weeks when it is performed at term. An error that is commonly made is to change a patient's due date on the basis of a third-trimester ultrasonogram. Doing so can result in failure to recognize IUGR.
| Symphysiofundal Height|| |
If the gestational age is known and is accurate, a low-risk pregnancy is followed up by serial measurements of the symphysiofundal height (SFH) as shown in [Figure 1]. Lag in SFH of 3 cm or more can help diagnose IUGR. Sensitivity varies 27%–85%. These features along with history and risk factors can guide towards evaluation with ultrasound.
SFH increases by 1 cm/week between 14 and 32 weeks. Serial measurements of SFH during antenatal checkup from 24 weeks are recommended as it improves prediction of an SGA fetus. Serial measurements of SFH are plotted on an SFH chart [Figure 2]. A customized chart is more reliable than a population-based chart. Women with a single SFH which plots below the 10th centile or serial measurements which demonstrate slow or static growth by crossing centiles should be referred for ultrasound measurement of fetal size.
The impact on perinatal outcome of measuring SFH is uncertain. A systematic review found only one trial with 1639 women which showed that SFH measurement did not improve any of the perinatal outcomes measured. Still, in a low resource setting, measuring the SFH is an important screening tool.
| Ultrasound Assessment of Fetal Growth|| |
Women in whom measurement of SFH is inaccurate because of factors such as obesity, fibroid complicating pregnancy, transverse lie, polyhydramnios, and multiple pregnancy, should be referred for serial assessment of fetal size using ultrasound.
While doing ultrasound the main parameters measured are biparietal diameter (BPD), head circumference (HC), abdominal circumference (AC), and femur length (FL).
The BPD should be measured on an axial plane that traverses the thalami, and cavum septum pellucidum. The transducer must be perpendicular to the central axis of the head, and thus, the hemispheres and calvaria should appear symmetric.
The calipers should be placed at:
- The outer edge of the near calvarial wall and
- The inner edge of the far calvarial wall.
The cerebellar hemispheres should not be in the plane of the image [Figure 3].
HC is measured on the same plane as BPD that is on an axial plane that traverses the thalami and cavum septum pellucidum. The transducer must be perpendicular to the central axis of the head, and thus, the hemispheres and calvaria should appear symmetric. The cerebellar hemispheres should not be in the plane of the image, or the probe will be too caudal giving an inaccurate size of the fetal head [Figure 4].
AC is measured by a transverse section through the upper abdomen, which should demonstrate the following fetal landmarks:
- Fetal stomach
- Umbilical vein
- Portal sinus.
The calipers should be on the skin surface (skin surface should be visible). The kidneys and cord insertion should not be visible. The umbilical vein should not be seen up to the skin line. The gallbladder may sometimes be seen [Figure 5].
Measurement of the FL is considered accurate only when the image shows two blunted ends [Figure 6].
The fetal weight is estimated from these parameters using the Hadlock's formula. AC and FL are the most important factors in determining fetal weight. Serial ultrasounds at 3 weekly intervals in a woman with risk factors help as a screening tool for assessing growth velocity of the fetus. Loss of or decreased growth is an important indicator of possible IUGR. Change in AC of <10 mm over a period of 2 weeks has a sensitivity of 85% and specificity of 74% of identifying IUGR.
| Amniotic Fluid Volume|| |
A quantitative estimate of amniotic fluid volume is an indicator of fetal well-being. It is a part of the biophysical profile. Amniotic fluid volume is assessed by calculating the four-quadrant amniotic fluid index (AFI) or by measuring single largest pocket of amniotic fluid.
Amniotic fluid index
AFI is calculated by adding the depth (in centimeters) of the amniotic fluid of 4 different pockets of fluid not containing the umbilical cord or fetal extremities in 4 abdominal quadrants using the umbilicus as a reference point and with the transducer perpendicular to the floor. Normal AFI-5–25 cm.
Deepest vertical pocket
DVP refers to the vertical dimension of the largest pocket of amniotic fluid (with a horizontal measure of at least 1 cm) not containing umbilical cord or fetal extremities and measured at a right angle to the uterine contour and perpendicular to the floor [Figure 7]. Normal DVP-2–8 cm.
Both RCOG and ACOG use single DVP to interpret amniotic fluid volume. However, it should not be the only form of surveillance in SGA fetuses and should be used in conjunction with other parameters.
| Growth Charts|| |
The estimated weight may be plotted on a chart during antenatal visits to serially monitor growth [Figure 8]. Charts built on a homogenous fetal population should be used. Customized growth charts make adjustments for maternal height, weight, parity, ethnic origin and fetal sex and are more reliable than general population-based charts.
What are customized growth charts
Customized charts delineate the Gestation Related Optimal Weight for each baby, by adjusting for characteristics such as maternal height, weight, parity and ethnic origin, and predicting the growth potential by excluding pathological factors such as smoking and diabetes.
These charts improve the antenatal detection of fetal growth problems, avoid unnecessary investigations, and reduce anxiety by reassuring mothers when growth is normal.
| Christian Medical College Protocol|| |
In the Christian Medical College, Vellore, the following protocol is used in the screening and antenatal assessment of IUGR.
In a low-risk pregnancy, serial measurements of SFH are done to decide which women will need ultrasound to diagnose IUGR.
Measurements for SFH are plotted on a chart at every visit. These are done till term, and those falling below 2 standard deviations or showing no linear growth are sent for ultrasound evaluation.
In a high-risk woman, or if SFH measurements are unreliable, serial ultrasounds are done at 28, 32, and 36 weeks of gestation.
| Conclusion|| |
- Determining the accurate gestational age is vital in the monitoring and management of all pregnancies and more so if suspected to have growth restriction
- Serial measurement of SFH is recommended in a low resource setting with ultrasound being used in the confirmation and diagnosis of IUGR
- Customized growth charts are recommended to serially monitor fetal growth.
The patient has been diagnosed with severe preeclampsia as well as suspected growth restriction.
Management of preeclampsia includes Inj. Magnesium sulfate 4 g slow IV as 20% solution followed by Inj. Magnesium Sulfate as 50% solution at the rate of 1 g/hr. She will also need to be given steroids to help with lung maturity.
An ultrasound will help in the confirmation of intrauterine growth restriction. In this case, an ultrasound examination showed a normal biparietal diameter and head circumference, although the abdominal circumference was 24.5 cm, which is at the 2.5th percentile. Estimated fetal weight was 1,465 g (3 lb, 4 oz), which placed the infant in the 3rd percentile. The amniotic fluid index was 6.0.
In secondary level setup, this patient will need referral to a tertiary level center where delivery will be considered 48 hours after the second dose of steroids.
Financial support and sponsorship
Conflicts of interest
There are no conflicts of interest.
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[Figure 1], [Figure 2], [Figure 3], [Figure 4], [Figure 5], [Figure 6], [Figure 7], [Figure 8]