Chorionic villus sampling CVS is an ambulatory procedure usually performed at tertiary centers to obtain samples of the placenta for genetic diagnosis. The procedure is carried out under ultrasound guidance trasvaginally or transabdominally. The approach is performed between 10 and 14 weeks of gestation by skilled and experienced operator. The procedure should be avoided before 10 weeks as it can increase the incidence of limb defect 1.2 and most abortions would have occurred before this time. It is also difficult to perform before this gestational age.
Amniocentesis is an alternative to CVS to obtain amniotic fluid which contains fetal cells for culturing and karyotyping. It is performed transabdominally under US guidance and is considered the most popular invasive procedure which should be done after completed 15 weeks of gestation. Early amniocentesis is associated with culture failure and fetal loss so it is better to avoid it 3
The main indications for genetic diagnosis include advanced maternal age, previous abnormal child, and family history of congenital abnormality as discussed in several studies 4. Other indications include abnormal US finding and soft tissue markers at aneuploidy screen. The most serious complication of CVS and amniocentesis is fetal loss which is reported around 1% 4,5.
The objective of the study is to study the trends in indications for invasive prenatal diagnostic procedures, and ultimately to look at the rate of miscarriages as an end point complication of the procedures performed and to compare the results to what has been reported in the literature.
Material and Methodology
Over a period of 5 years 943 Jordanian women underwent diagnostic prenatal procedures in the tertiary center of fetal medicine at King Hussein Hospital, Royal medical services which is considered a referral center to all military hospitals in Jordan. This is a retrospective review of all invasive procedures between 2013 and 2017. All patients who underwent CVS for thalassaemia and all patients who underwent molecular DNA testing and their samples were send outside Jordan for analysis were excluded from our study.
The first trimester screen which involves calculating the risk of having a baby with Down syndrome involves B-HCG, PAPPA, Nuchal translucency and maternal age is not offered at our center. Patients who are interested in doing the test are asked to go to a private laboratory to have it done. None invasive prenatal diagnosis is not offered at our centre and all tests were done privately.
Procedures performed included amniocentesis done after 15 weeks and CVS done between 11-14 weeks respectively which were done by 3 experienced consultants. Cordocentesis procedures were excluded from the study due to the lack of experience of certain consultants in this procedure and due to the increase risk of miscarriage associated with it compared to other procedures 6.
After explaining to the women the risks of the procedure (pretest counseling). The procedures were performed under US guidance and aseptic technique transabdominal approach only, using a spinal needle G 18-20 for amniocentesis and G18 for CVS. Prophylactic antibiotic was not prescribed. Local anesthesia was given only to patients who underwent CVS. All patients were given appointments to be seen in clinic in one week after the procedure to discuss the early results and to follow up results and to assess complications. Following the procedures, the patients were asked to notify the center should any sign or symptom of complications appear. All procedures were recorded in a specific form which was divided into two parts, one was filled in the clinic which included the maternal age, parity, gestational age, indication for the procedure, procedure performed, test requested, any complication at the time of the procedure and a positive fetal heart for the reassurance of the mother at the end of the procedure. All the patients with negative blood groups were given Anti D immunoglobulin. The second part is filled at the laboratory which includes the results and saving the data into a specialized registry for follow up and auditing purposes.
The indications of performing the procedures were as follows:
1. Advanced maternal age (AMA); age of the pregnant women 37 years and above
2. Family history of congenital abnormalities and/or history of abnormal offspring
3. Abnormal US findings; Polyhadraminos, IUGR, Cystic hygroma, Renal abnormalities, CNS abnormality, and others
4. Abnormal integrated tests; first trimester (PAPP-A and nuchal translucency) and second trimester (serum AFP, UE3,beta_hCG,inhibin A)
5. Soft tissue markers of aneuploidy on scan
6. Family history of Down syndrome
The study was approved by our local ethical committee at the Royal Medical Services.
This study was conducted in the fetal medicine unit at King Hussein Medical Hospital where diagnostic procedures were done by 3 operators at a rate of 60 cases annually each. This is above the standard rate (usually around 30 cases per year) 7. The maximum number of procedures was done in 2016 where the number of cases was 211, on the other hand, the lowest number of procedures was in 2017 reaching 166 cases as shown in Chart 1.Chart 2 shows the number of abnormal cytology detected at our unit, showing the highest at 25 cases in 2014 and the lowest at 8 cases in 2013. Fig 1 shows the type of abnormalities detected over a 5 years period where the maximum number is 29 cases of Down syndrome.Figure 2 shows indications of procedures annually between 2013 and 2017. Table 1 compares the percentage of CVS cases to AC throughout the five years showing a roughly three-fold prevalence of AC at 74.7% over CVS at 25.2%. Table 2 compares the percentage rate of miscarriage associated with both procedures over five years period. The percentage of miscarriage occurrence with CVS is at 1.26% compared to miscarriage rate of 0.28% for AC. Table 3 shows the frequency of the abnormalities detected in relation to the indication of procedure.