Follow-up on pregnant women with CMV
There are currently three tests that allow monitoring of a fetus whose mother has been infected with CMV.
One test is amniocentesis, which is highly reliable for diagnosing fetal infection up to the time of testing, but it does not determine whether the fetus has been harmed by the infection.
The other tests are targeted ultrasound scans and fetal brain MRI. If their results are normal, they can almost certainly rule out severe injury to the newborn. See Articles tab.
1.Amniocentesis – This test can detect CMV in the urine excreted by the fetus, which helps determine whether the fetus has been infected.
It is preferable to perform the test after week 21 of pregnancy, provided that at least seven weeks have passed since the estimated time of maternal infection. In addition, initial research evidence suggests that if the mother was infected around conception or early in the first trimester, the test sensitivity will also be high when performed at the usual timing of amniocentesis (weeks 17 to 20). Therefore, the doctor may consider performing the test earlier
Between weeks 24 and 32, the test is generally not performed in Israel due to the risk of preterm birth caused by the procedure. Preterm delivery at such an early gestational age carries significant risks unrelated to CMV.
If the couple does not wish to perform amniocentesis for CMV, it is recommended to follow the same protocol used for a positive amniocentesis result and conduct imaging based monitoring. The physician may consider performing amniocentesis later in the pregnancy only if signs of fetal injury appear.
Testing the amniotic fluid for CMV uses the same procedure as a standard genetic amniocentesis, with one difference: an additional vial of amniotic fluid is collected and sent to a virology laboratory.
If the maternal infection occurred after week 16 and because the risk of fetal injury from such an infection is low, the doctor may choose imaging follow up only.
Women who undergo amniocentesis at week 32 will be asked to receive two injections to promote fetal lung maturation a few days beforehand. After the procedure, the woman will remain under observation and be connected to a fetal monitor for about thirty minutes. In addition, the procedure must be performed in a hospital with delivery facilities, with an additional physician present. This detailed protocol ensures that if any complication arises, the fetus can be treated in the optimal way.
It is important to obtain Form 17 both for the amniocentesis and for the virology laboratory.
The CMV infection test result is usually returned within a few days.
Whenever maternal infection occurs during pregnancy, it is recommended to perform a urine or saliva test for the newborn after birth. Details of these tests can be found in the Birth and Time in the Neonatal Department tab.
If amniocentesis is negative, there is still an approximately eight percent chance of fetal infection. However, since the assumption is that infection occurred after the procedure, meaning during weeks when injury is not expected, recommendations range from the more lenient approach of performing only a newborn saliva or urine test after birth to the more cautious approach of performing one targeted ultrasound scan around weeks 30 to 32.
A list of hospitals where the test can be performed can be found in the Important Telephone Numbers tab
2. CMV targeted scans –
The targeted scans are performed starting from week 24 at intervals of approximately four weeks until weeks 34 to 36. These scans focus on identifying signs that indicate fetal injuries characteristic of CMV.
Targeted scans are performed if the amniocentesis result is positive for the presence of CMV, or in cases where the woman chose not to undergo amniocentesis but a maternal CMV infection during or near pregnancy is known.
The exact timing for beginning the targeted scans will be determined by the specialist monitoring the pregnancy, based on the gestational week in which the mother became infected.
It should be noted that choosing the physician who performs the scan is highly important, since this evaluation relies on the examiner’s experience with fetuses infected with CMV in general and with fetal brain assessment in particular.
3. MRI (magnetic resonance imaging) of the fetus brain
This test is performed at weeks 32 to 34 of pregnancy in cases where the fetus has been infected with CMV, or when the mother chose not to undergo amniocentesis but a definite maternal infection during or near pregnancy is known.
This test requires special performance and interpretation, and it is not available in every hospital. A list of hospitals where the test is performed can be found in the Important Telephone Numbers tab.
Some hospitals instruct women to take a Valium tablet before the test in order to reduce fetal movement and improve the likelihood of obtaining accurate results.
The leading experts in Israel in fetal imaging for CMV believe that consistency between findings from targeted ultrasound scans and the fetal brain MRI supports the diagnosis, whether suspicious findings are present or not.
A lack of consistency between these findings regarding possible injury due to infection will lead to discussion about the possibility of false results, especially false positives.
Follow-up protocol
The follow-up protocol for a woman who contracts CMV for the first time during pregnancy depends on the week of infection.
Infection more than three months before conception – is currently considered safe, and most experts do not recommend any special CMV testing, except for performing a urine test for the newborn.
Infection about two to three months before conception – it is usually recommended to perform one targeted ultrasound around week 32, and after birth, a urine test for the newborn.
Infection from one month before conception up to week 16 of pregnancy- it is usually suggested to perform amniocentesis after week 21, and further follow-up will depend on the test result:
– Negative amniocentesis – indicates that the fetus was not infected up to the time of the test. Even if infection occurs later in pregnancy, in most cases there will be no severe damage.
In this case, a targeted scan at weeks 30-32 is recommended for additional reassurance.
In any case, a urine test after birth is recommended to rule out late infection.
– Positive amniocentesis – the full testing protocol will be initiated, including targeted scans for CMV from week 24 until weeks 34-36, and a fetal brain MRI at weeks 32-34. Despite a positive amniocentesis result, hospitals still perform a urine test when the baby is born, but they do not wait for the result and begin the tests described in the Birth and Time in the Neonatal Department tab.
It is herein stressed that no two cases are alike, and the attending doctor manages the follow-up of the pregnancy according to the level of risk, and according to the wishes and beliefs of each woman.
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