Indications for Growth Scans in the High Risk Clinic
Indications for Growth Scans in the High Risk Clinic
Indications for growth scans based on SFH monitoring
24 weeks to 32 weeks Growth Scan Generally not Indicated
Growth Scans after 32 weeks based on SFH
"Routine" Growth Scans After 32 Weeks (Regardless of SFH) in the Presence of Normal UAD
"Routine" Growth Scans After 32 Weeks in Diabetics at the High Risk Clinic
Rationale
This guideline aims to decrease the number of unnecessary (not clinically indicated) growth scans being performed in the HRC and to subsequently reduce workload & pressure on the clinic. When deciding on whether a growth scan is indicated, always carefully assess gestational age before requesting a growth scan.
Indications for Growth scans based on SFH monitoring
- SFH <p10 for GA as per gravidogram, as a new finding since the last examination
- 3 SFH measurements that plateau (even if not crossing p10) over at least a two week period
- Current SFH that is less than SFH 2 visits previously (even if not crossing p10)
It is acknowledged that SFH monitoring alone is not sufficient to detect fetal growth restriction, especially in pregnancies at high risk for placental insufficiency.
24 weeks - 32 weeks: Growth Scans Generally Not Indicated
Umbilical artery Doppler (UAD) is the investigation of choice to exclude early onset growth restriction (24 -32 weeks). Therefore, if SFH is suggestive of growth restriction, the initial investigation is UAD, NOT a growth scan.
UAD is performed routinely (irrespective of SFH) at 24 – 32 weeks for previous:
| IUGR baby | Eclampsia |
| Unexplained stillbirth | Pre-eclampsia |
| Preterm birth (not due to cervical incompetence) | Abruptio placentae |
Conditions requiring UAD at 24-32 weeks (irrespective of SFH) in the current pregnancy:
| Diabetes | Morbid Obesity BMI >40 |
| Chronic hypertension | Auto-immune diseases |
| Gestational hypertension |
If the UAD is normal in these conditions, current early onset IUGR has been excluded and a growth scan is not necessary. This situation needs to be reassessed after 32 weeks.
Growth Scans After 32 Weeks Based on SFH
UAD monitoring must still be done but will often not detect late onset IUGR (beyond 32 weeks).
If SFH is less than P10 for gestational age or plateauing beyond 32 weeks (see above), then a growth scan should be performed.
At the growth scan, ALL fetal biometry measurements (BPD, HC, AC, FL as well as EFW) should be taken, recorded on the formal ultrasound report form AND plotted against centiles for gestation (also plot the previous ultrasound measurements to look at trends). The AFI should also be measured.
The SGA protocol should then be consulted to determine management.
Growth scans should not be repeated outside the protocol and not sooner than 3 weeks apart.
"Routine" Growth Scans After 32 Weeks (Regardless of SFH) in the Presence of Normal UAD
In certain patients, SFH monitoring is insufficient for accurate exclusion of fetal growth restriction. In these cases, a routine growth scan at 36 weeks will best detect late onset placental insufficiency.
Patients at particularly high risk of IUGR should also receive routine late growth scans:
| Super morbid obesity (BMI >50) |
Abnormal uterine artery Doppler earlier in the pregnancy |
| Morbid obesity (BMI >40) with hanging pannus or difficult to palpate uterus | Previous severe or early onset (pre)eclampsia |
| Multifibroid uterus (if fibroids large) | Previous abruption |
| Hypertensive conditions | Previous late IUGR |
| Previous unexplained stillbirth |
These patients should receive one growth scan only, at 36 weeks. If growth is good, there is no need to repeat a growth scan unless a new clinical problem arises.
"Routine" Growth Scans After 32 Weeks in Diabetics at the High Risk Clinic
Diabetic mothers should receive UAD monitoring at 24 -32 weeks, then a growth scan at 36 weeks to assess for late placental insufficiency or macrosomia and to determine mode of delivery. EFW for mode of delivery can also be assessed clinically at late pre-term/ early term for these patients, especially if the abdomen examines well.
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Tygerberg Hospital, Department of Obstetrics and Gynaecology; Guideline for indications for growth scans in the high risk clinic; Version: July 2018; Last checked for updates by EMGuidance: Oct 2023