J Med Genet: first published as 10.1136/jmg.24.6.335 on 1 June 1987. Downloaded from Journal of Medical Genetics 1987, 24, 335-343 Midtrimester genetic amniocentesis in Eastern Ontario: a review from 1970 to 1985 ALASDAIR G W HUNTER, DIANE THOMPSON, AND MARSHA SPEEVAK From the Division of Genetics, Children's Hospital of Eastern Ontario, Ottawa, Canada KJH 8L1. SUMMARY Greater use of genetic amniocentesis in the Eastern Ontario region occurred once the results from the various national trials were published.1-3 Acceptance also paralleled an increase in the number of low parity older women having children and the centralisation and greater publicity given to our programme in the late 1970s. A centralised approach has had the positive effects of preventing unnecessary procedures, assuring appropriate patient counselling, follow up, and review, and of increasing obstetric and laboratory expertise. Advanced maternal age has been largely responsible for the increased demand for the service and accounted for an increasing proportion of tests performed, while the absolute number for several other diagnostic categories remained unchanged. We found no evidence that women with a history of previous miscarriage had a higher rate of pregnancy loss following the procedure, and comparison with a group of women who declined amniocentesis did not show that the test increased the risk of miscarriage. copyright. Genetic amniocentesis was first offered in Ottawa in Methods 1970. From then until the end of 1985, 4084 women contacted the Division of Genetics and 3275 of them Only three amniocenteses were carried out in Ottawa underwent the procedure. By 1 January 1979 over 20 before the beginning of the Canadian MRC study in obstetricians had performed a total of 370 tests, and January 1972, which introduced specific data col- the early cases were contributed to the Canadian lection forms and the requirement that patients be http://jmg.bmj.com/ Collaborative Study.' In 1979 area obstetricians followed up. The cytogenetic laboratory continued to agreed to have five of their colleagues (in three use these forms after the study ended in 1975, hospitals) perform all amniocenteses and to have the although the data were not always complete. After counselling and record keeping centralised through the programme was centralised in 1979, all pro- the Division of Genetics at the Children's Hospital of cedures were booked through the Division of Eastern Ontario. The aim was to ensure that patients Genetics and most patients were formally counselled there. New forms were introduced which allowed made informed decisions about amniocentesis, that on September 27, 2021 by guest. Protected the guidelines on indications were followed, and that easy entry of data into a dBase II computer file. One obstetric expertise was maximised. In January 1983 of the participating obstetricians continued to do his the laboratory changed from flask subcultures to in own counselling for advanced maternal age (AMA) situ colonial analysis. This reduced the rate of but used the same forms. Data routinely collected reported mosaicism, increased the case load handled included: gestation at visit and at tap, by dates and per technologist, and decreased the turn around time by ultrasound, and at delivery; age at delivery, past for samples. In 1985 there was renewed interest in the pregnancy, and family history, and reason for the safety, efficacy, and acceptability of genetic amnio- procedure; and recent radiation, drug, alcohol and centesis because of the growing medical promotion smoking history, type of counselling, and Rh status. and public acceptance of chorionic villus sampling, In addition, information as to whether a tap was with which it is compared. We therefore thought this attempted, the number of insertions required, the an opportune time to review our experience with quality and quantity of fluid obtained, placental amniocentesis. location, and various laboratory procedures were recorded. Follow up included standard information Received for publication 15 April 1986. on pregnancy outcome and complications, birth Accepted for publication 30 May 1986. weight, and the attitude of the patient to the 335 J Med Genet: first published as 10.1136/jmg.24.6.335 on 1 June 1987. Downloaded from 336 Alasdair G W Hunter, Diane Thompson, and Marsha Speevak procedure. The reason why a patient who had been Results counselled declined the test was noted, as was the discovery of a dead fetus at the time of the tap. DEMOGRAPHIC TRENDS Starting in 1982, a record was kept of women who Fig 1 shows, by year, the number of women giving declined amniocentesis and counselling when first birth at or over the age of 35 years (AMA) in our contacted for an appointment. Cases were sum- catchment area, which has about 15 000 deliveries a marised and reviewed twice a year. A concerted effort year. It also gives the number and percentage of was made at the time of each review to update follow AMA women who underwent the procedure, and up information, and separate attempts have been finally the total number of women per year who made on several occasions to find missing data, underwent amniocentesis. Genetic amniocentesis including during the course of this review. was introduced at a time when the age specific Data were analysed using the standard logical fertility of women of 35 and over was falling search formats of dBase II as well as command rapidly.4 Only a small fraction of these women had programmes normally used for an annual review of amniocentesis. The numbers began to show a the outcome of patients referred to the prenatal marked rise in 1976 to 1977 and this coincided with programme. For purposes of several comparisons, the publication of a number of surveys attesting to the data have been divided into pre-1979, 1979 to the relative safety of the test, -3 as well as the 1982, and 1983 to 1985. At the time of writing many centralisation of the programme in mid-1979. How- patients tapped in 1985 were yet to deliver, and so ever, more important was the fact that a cohort of data concerning miscarriage risks and follow up end educated women, who had postponed their families, on 31 December 1984. began to have children in large numbers. Thus, to copyright. No of women _ 35 years at delivery (00-0) V/. of women ¢ 35 years having amniocentesis - -- No of women having amniocentesis --- Noof women > 35 years having amniocentesis (0.07) Estimated 1294 * (51.1) http://jmg.bmj.com/ 1200 1200* (45.5)/-" 1087 (0.5) (43.1 1000 993(4.1)993 ~~~~~~~~~~~~(39.7)979 (0.0) (.)902 845.......840 (1.9) (30.3>.... C 800I 789 (5.2) (2.-...0 E -749 (7.4) ( 17.3) 743 on September 27, 2021 by guest. Protected 0w 698 (15.8) 694 721 600 , ,613 0 570 0 z 483, 495 . 422 400 426 301 ' 358 200 253 245 153---160 .179 .97S 103 -120 nn% -~ v 71 72 73 74 75 76 77 78 79 80 81 82 83 84 85 Year FIG 1 No of women giving birth at or over 35 years by year. J Med Genet: first published as 10.1136/jmg.24.6.335 on 1 June 1987. Downloaded from Midtrimester getnetic amniocentesis in Eastern Otntario: a review frotn 1970 to 1985 337 some extent, the increase in amniocenteses per- gravidity represented a small group with low utilis- formed paralleled the rising age specific fertility of ation throughout the period of study. The fact that women over 35. The percent usage has also increased the proportion of gravida 1 women was higher before steadily to the point that in 1985 we estimate that 1979 than after suggests that the pre-1979 period was just over 50% of AMA women had an amniocentesis the beginning of the 'career delayed baby boom'. and that about 70% were in contact with our Although advanced maternal age has always been department. the most common indication for genetic amnio- The data have been divided into the three time centesis, its relative dominance has continued to periods previously described so as to provide a increase over the years from 60(% before 1979 to its number of comparisons: pre-1979, 1979 to 1982, and current level of 851% (table 2). Initially, women who 1983 to 1985. Table 1 summarises the gravid status of had already had an abnormal child were propor- all women referred to the programme and provides a tionately more likely to be tested and the actual separate tabulation for those referred for AMA. For number of tests performed for such indications has all periods, and regardless of indication, almost half remained relatively constant, with the exception of a the amniocenteses were performed during a first or decline in testing for neural tube defects in second second pregnancy. We had anticipated this would be degree relatives (largely replaced by ultrasound and the case for the latter years but had expected a higher serum a fetoprotein screening). Few women in our proportion of multigravid women before 1979. For region have had amniocentesis for fetal sexing example, in 1970, only 8.8% of Ontario women because they were at risk of transmitting an X linked delivering over the age of 35 were primiparas, and in disease. The minimum 50% probability that a male 1977 the figure was 16%.4By contrast, 29-8% of our would be unaffected seemed to be the major deterent. pre-1979 AMA mothers were gravida (the per- Tests performed for inappropriate reasons were centage who would be para 1 would be even higher). eliminated once the programme was centralised in Thus it appears that even before 1979 a large 1979. proportion of AMA women using amniocentesis The age distribution of patients has paralleled the represented women who had postponed their families shift in the indications.