Louis Graydon  DCR(R), DMU  Superintendent Sonographer, Friarage Hospital, Northallerton, England, DL6 1JG

Key Words: amniocentesis; maternal age; obstetric risk; ultrasound; pregnancy; genetics

Introduction

Amniocentesis is useful for prenatal diagnosis in conditions like maternal Rhesus iso-immunisation; gender determination and chromosome studies ⁽¹⁾. Many obstetric units offer this test to pregnant women. There are however risks associated with this procedure ^(2). The Obstetric & Gynaecology department in Northallerton, North Yorkshire, England serves a rural population of about 122,000.  Between 1992-2001, the departmental staff comprised 3 consultants, 2 Associate Specialists and a series of Senior House Officers spending between 6-12 months.  The annual delivery rate was about 1300 babies and caesarean section rate was 20%.  Midwives conduct a large percentage of deliveries and there are opportunities for delivery in a waterpool.  As part of the antenatal care given to pregnant women, amniocentesis is offered where indicated.  Prior to this procedure, there is proper counselling by doctor/midwife and the patient gives written consent.

Audit

Auditing in a small district hospital when numbers for specific examinations are small in comparison to large teaching centres can be a challenge ^(3).  A 10-year audit on Amniocentesis carried out at the Friarage Hospital, Northallerton, North Yorkshire is reported in this article.  The hospital has approximately 300 beds and serves a large rural area close to the Yorkshire Dales and Moors.  The aim of the audit was to:

1.                  Evaluate whether care and standards can be maintained when an average of 3-4 amniocentesis were performed a month.

2.                  Monitor the indications for amniocentesis

3.                  Record the outcome - either at delivery or termination.

4.                  Monitor risk.

Indications for amniocentesis

There were several indications for amniocentesis.  These included: positive triple test; maternal age; increased nuchal translucency measurement; anomaly detected on scan; Rhesus iso-immunisation and previous chromosomal abnormality. The majority of cases were referred because of a positive triple test.  From 1992 until 2000 the number of referrals due to maternal age became greater than those for Triple Test, maternal age being classified as mothers over 38 years of age or older.

Method/Procedure:

The patient is fully counselled before the amniocentesis about the risks of miscarriage, the procedure itself and the timescale involved in receiving the results.

An ultrasound scan is performed to establish placental / foetal position and confirm gestation and viability. An entry site is marked using a skin marker.

 Using aseptic technique and under direct real time ultrasound guidance a 22 gauge spinal needle is introduced without using local anaesthetic. The needle tip is followed to the target amniotic pool avoiding the placenta whilst also keeping a careful watch of foetal movements. 10 – 15 mls. of clear amniotic fluid is withdrawn, the needle is removed and a small plaster is placed over the needle entry. A further scan is performed to observe foetal heartbeat and movements and to reassure the patient. This procedure has been previously reported by

 other clinicians ^(2,4,5). The patient is given instructions to  rest for 24 hours with no lifting or driving and informed how she will receive her results. The sample is taken to the pathology department at the Friarage Hospital from where it is then taken by car to the Cytogenetic Unit at St. James’ Hospital, Leeds a journey of about 50 miles. High risk patients, or patients whose triple test result is 1:100 or less, or late amniocentesis of 18 weeks or over are offered a quick result within 48 hours using FISH technique. Patients who request quick result from the PCR test done in London had to pay the cost because this test is not available on the National Health Service.  Results for those samples requiring full culture take approximately 2-3 weeks to come through.

 Number of Amniocentesis per Year.

1992 – 27

1993 – 53

1994 – 44

1995 – 53

1996 – 46

1997 – 39

1998 – 52

1999 – 47

2000 – 55

2001 – 55

 

 

Results/Outcomes:

These are shown in the figure and tables. The number of amniocenteses doubled between 1992 and 1993 then fluctuated between 39 and 55 over the following years.  The number remained at 55 for 2000 and 2001.  Some patients undergoing amniocentesis were carrying twins. Out of the 471 amniocenteses performed during the 10-year period, 444 (94%) were carried out by the same 3 clinicians.   The remaining 27 amniocenteses, these were performed by about five other doctors but under the direct supervision of the 3 main clinicians responsible for amniocentesis.

  The results for 433 patients (92%) were of normal karyotype. Out of the remainder, 19 (5%) were lost to the audit. It must be recorded that there were some cases where the outcome was normal with abnormal karyotype or the outcome was abnormal with a normal karyotype.

However, in 411 patients (87%), were known to have a normal outcome- live births and normal karyotype babies. Thirty-eight patients had abnormal karyotypes. There were 12 terminations of pregnancies and one miscarriage. Five people had abnormal karyotypes but carried the pregnancies to term- (1 chromosomal translocations, 1 trisomy, 1 mosaic Turner and 1 Turner's syndrome.)

There was 1 miscarriage as a direct result of amniocentesis over the 10-year audit.  (0.2%), which is significantly better than the national average of 1% risk of miscarriage.(Ref.)

Table: Main outcomes

Condition	Number
Trisomy  21	14
Trisomy 13	1
Turner's	2
Translocations	2
Klinefelter's syndrome	1
Osteogenesis imperfecta	2
Cleft palate/lip	1
Fracture	1

Indications and Results

Triple Test

Of the 290 screen positive triple tests 13 (4.5%) had abnormal karyotype.  11 screened positive for Trisomy 21.  There were 9 terminations in this group and 2 carried to term.

1 - translocation between Ch14 and Ch21.

1 - extra material on the short arm of Ch22.

Maternal Age

Of the 112 amniocenteses performed for maternal age, 109 (97%) had a normal karyotype.  106 had normal babies.

2 were lost to the audit.

1 miscarried 3 weeks after the amniocentesis

Of the 3 with abnormal karyotype:

1 – 47 XXY Kleinfelter’s (termination)

1 – screen positive for Trisomy 21 (Carried to term)

1 – mosaic for Turner’s (carried to term)

Increased Nuchal Translucency

Total number was seven.  Six had normal babies and 1-screened positive for Trisomy 21 (termination)

Abnormalities seen on Scan

These included a range of anomalies:

1 – fractured femur with normal karyotype.  Outcome – fractured femur

1 – Cleft palate/lip with normal karyotype.  Outcome – cleft palate/lip

There were 3 patients with cystic hygromas and generalised skin oedema.

1 – screened positive for Turner’s syndrome.  Outcome – Turner’s syndrome

1 – screened positive for Trisomy 21.  Outcome – termination

1 – screened positive for Trisomy 13.  Foetus died in utero.

Skeletal Dysplasia

One patient - The cells failed to grow.  Outcome – termination at 21 weeks for osteogenesis Type II

Iso-immunisation

Of the 15 patients sampled, none were karyotyped.  All babies are doing well.

Comments and discussion

This audit gives an indication of how standards can be maintained by a dedicated team of specialists.  In 2002 Northallerton Health Services NHS Trust of which the Friarage Hospital was part, merged with South Tees NHS Trust, thus becoming part of a large teaching hospital trust.  It is unlikely that an intimate and consolidated audit involving small numbers of patients and staff would ever be achievable in the future. While such an audit is useful, it can cost a lot in terms of money and time (3).

References

1. Nicolaides K, Brizot M, Patel F, Snijders R. Comparison of chorionic sampling and amniocentesis for foetal karyotyping at 10-13 weeks gestation. Lancet 1994; 344:435-9.
2. de Crespigny LC, Robinson HP. Amniocentesis: a comparison of monitored amniocentesis versus blind needle insertion. Aust N Z J Obstet Gynaecol 1986; 26:124-8.

3. Weiner JJ, Farrow A, Farrow SC. Audit of amniocentesis from a district general hospital: is it worth it? BMJ 1990; 300(6734): 1243-5.

4. Romero R, Jeanty P, Reece EA et al. Sonogrsphically monitored amniocentesis to decrease intraoperative complication. Obstet Gynaecol 1985; 65: 426-30.

5.The Canadian early and Midtrimester Amniocentesis Trial (CEMAT) group Randomised trial to assess safety and fetal outcome of early and midtrimester amniocentesis. Lancet 1998; 351(9098): 242-7.