Screening for Pre-eclampsia and Foetal Growth Restrictions
MedPiper Technologies and JournoMed had conducted a World Pre-eclampsia week Webinar Series in association with National IRIA Preventive Radiology and Samrakshan Committees where the speakers addressed topics of Pre-eclampsia and Foetal Growth restriction Screening on 25th May, 2022.
Dr. Shilpa Satarkar, MD Radiology, spoke about the core theme of the Samrakshan Program which aims to reduce perinatal mortality in India. The major causes for high mortality rates includes low birth weight and prematurity due to pregnancy hypertensive relative disorders aka pre-eclampsia. Pre-eclampsia can be life threatening and devastating and can deteriorate maternal health within a single day.
In most mothers suffering from the condition, pre-eclampsia can cause abruptio placentae, pulmonary oedema, hepatic and renal issues. While in foetus, it leads to foetal growth restriction, prematurity and other complications. In children exposed to pre-eclampsia before birth, there is an increased risk of cerebral palsy, cardiovascular disease, having high body mass index, and diabetes. All these complications can be treated by developing effective methods for predicting pre-eclampsia aka Pre-eclampsia Screening.
A major purpose for pre-eclampsia screening is to detect the condition and to prevent its progression. Timely effective care improves pre-eclampsia outcomes. The early proposed treatment institution of aspirin improves perinatal outcomes in nearly 60-80% cases.
Pre-eclampsia is a multi system syndrome developed during the second half of the pregnancy. It is characterized by hypertension, proteinuria and maternal organ dysfunction. This condition can be further divided into three types based on when it occurs during the term of pregnancy:
- Early onset pre-eclampsia occurs in less than 32-34 weeks
- Preterm pre-eclampsia occurs in less than 37 weeks
- Term pre-eclampsia occurs later than 37 weeks
During screening, the foetal growth restriction pattern and the maternal environment is being monitored. During pre-eclampsia, maternal health is affected.
Placentation is a two stage process. In the first stage, placentation starts at 8 weeks and ends by 14 weeks. The trophoblasts invade the spiral arteries in the decidua. In the second stage, placentation starts at 14 weeks and ends by 18 weeks. The trophoblasts invade the spiral arteries in the myometrium. By observing the channel formation in the decidua and the myometrium, doctors can determine if it is normotensive or pre-eclampsia condition.
In hypoxia conditions, blood circulation of placenta reduces and its structure is slightly altered. Due to this defective remodeling, certain proinflammatory toxins are released in the maternal environment. These toxins damage the endothelium of the blood vessel, resulting in hypertension and end organ damage.
Aspirin increases the number of blood vessels by inducing neural blood vessel formation in the placenta. All these occur in the placenta and therefore it reduces the risk of hypertensive disorders and its complications.
What ultrasound assess performed in the first trimester scan?
The first trimester scan can be taken between 11-13 weeks of pregnancy. Physicians look for aneuploidy, structural defects, pre-eclampsia and foetal growth restriction along with screening for preterm labor. Currently, FMF method of screening is preferred for pre-eclampsia. Radiologists follow sonography as per the Samrakshan Protocol and guide pregnant women in filling up the Samrakshan forms
Screening pre-eclampsia parameters (FMF recommendations)
The following are the screening parameters for pre-eclampsia at present.
- Maternal characteristics
- Mean arterial pressure
- Uterine artery PI
- The biochemical marker tests such as PAPP-A, PLGF, s FLT1
Screening for pre-eclampsia and foetal growth restriction
Screening for Pre eclampsia and the foetal growth restriction is a five step approach.
- Step 1: Taking maternal history
- Step 2: Measuring mean arterial pressure (MAP)
- Step 3: Uterine artery doppler performed at 11-14 weeks
- Step 4: Calculating the patient specific risk for pre-eclampsia and foetal growth restriction
- Step 5: Filling up of the Samrakshan forms to gather our own data and set own guidelines
How to take the mean arterial pressure?
Women are to sit comfortably and blood pressure is taken on both arms simultaneously using the Sphygmomanometer. The series of two recordings must be taken at 5 min intervals and minimum 2 readings can be utilized.
Mean arterial pressure (MAP)= Diastolic blood pressure + (Systolic blood pressure – Diastolic blood pressure)/3
Add all the readings of maternal characteristics in the FMF calculator. The two measurements of the systolic and the diastolic blood pressures are calculated for both the arms. The system automatically calculates the mean arterial pressure ( MAP).
After calculating the mean arterial pressure (MAP) along with the maternal characteristics, the detection rate for various types of pre eclampsia is determined. Early onset preeclampsia is 74% for nearly less than 34 weeks, for preterm preeclampsia is 63% for 34-37 weeks and for late onset preeclampsia is 49% for greater than 37 weeks of gestation.
Uterine Artery PI
Uterine artery PI is measured using the uterine artery doppler. The most preferred scan is the transabdominal scan. Radiologists at Samrakshan recommends pregnant women to go for combined uterine artery doppler and not for solitary uterine artery doppler as the marker scan. Under the program, biochemical measurements were not included.
The use of biochemical markers are independent of the detection rates. Biochemical markers such as placental growth factor (PLGF), serum soluble FMS-like tyrosine kinase -1 (sFLT-1), pregnancy associated plasma protein- A (PAPP-A) etc. are analysed during the first trimester scan. These factors are involved in placental growth and development.
The combined multimarker screening and randomized patient treatment with Aspirin for evidence-based pre-eclampsia prevention (ASPRE) trial has demonstrated that Aspirin – 150 mg/ day prescribed at night to high risk women at 11-13 weeks till 36 weeks can delay pre-eclampsia.
Samrakshan- An IRIA Initiative
Samrakshan is a national initiative by IRIA to reduce the perinatal mortality in India. This integrates foetal imaging studies with childbirth planning with a focus on pre-eclampsia and foetal growth restriction. Pre-eclampsia and foetal growth restriction are major causes of high prenatal mortality rate in India. A systematic phased approach is designed to train and guide the radiologists in India for pre-eclampsia and foetal growth restriction screening using ultrasound and colour doppler, at 3rd month and 8th month respectively to identify these risks.
Pre-eclampsia and foetal growth restriction screening during the first trimester must be done in all pregnancies. Samrakshan Program is a categorical package that integrates foetal growth parameters and the foeto maternal environment assessment where the main focus is only on structural and chromosomal anomalies. The program provides another dimension to the pregnancy scans by detecting foetal growth abnormalities, hence preventing perinatal deaths.