EUROP. J. OBSTET. GYNEC. REPROD. BIOL., 1979,9/2,65-74 @ Elsevier/North-Holland Biomedical Press

Cytogenetic investigationin 413 couples with spontaneous abortions C. Turleau.

F. Chavin-Colin

Unit6 de Recherche

INSERM

and J. de Grouchy

U.173 and E.R.149,

CNRS, Hbpital des Enfants-Malades, Clinique de GBnPtique Mkdicale, 75 730

Paris Cedex 15, France

Accepted for publication 3 October 1978 TURLEAU, C., CHAVINCOLIN, F. and de GROUCHY, J. (1979): Cytogenetic investigation in 413 couples with spontaneous abortions. Europ. J. Obstet. Gynec. reprod. Biol., 912, 65-74. 413 couples with one or more spontaneous miscarriages were kayotyped. Observed chromosomal rearrangements were classified as major rearrangements,i.e. Robertsonianand reciprocal translocations,pericentricand paracentricinversions,supernumerary small metacentrics, and minor rearrangements, i.e. pericentric inversions of chromosome 9, and constitutional fragility of particular chromosome sites. 2.30% of the individuals were carriers of a major rearrangement, which represents a ten-fold increase when compared to the general population. The contribution of each type of rearrangement is unequal, the most important being pericentric inversions (36 times more frequent than in the general population). Contrary to data from the literature, the probability of finding a rearrangement does not seem to increase with the number of miscarriages. chromosomes; spontaneous abortions; reproductive failure

Introduction

There is, however, a small percentage of cases in which a structural rearrangement is detected in the unbalanced state in the abortus and in the balanced state in one of the progenitors. In this event the risk of recurrence is high, and indeed cytogenetic investigations of couples having experienced recurrent abortions show an increase in structurally balanced rearrangements as compared to the general population. Series which have been reported by a variety of laboratories concur in showing an overall ten-fold increase of such rearrangements. However, these series are of relatively small sizes, and give little information on the obstetrical histories of the couples and on the relative importance of the different types of chromosomal rearrangements (Winigate, 1965; Bishun and Morton, 1968; Pergament, Kadotani and

The importance of chromosomal aberrations as possible causes of fetal wastage was first demonstrated by systematic cytogenetic investigations of spontaneous abortuses (Carr, 1963; BouB, Bout! and Lazar, 1967; Boue and Boue, 1975; BouC, Daketse, Deluchat, Ravise, Yvert and Baud, 1976). It is now considered that 60-65% of detectable spontaneous miscarriages occurring during the first trimester are due to chromosomal aberrations. These aberrations are mostly numerical, trisomies in particular, and are essentially de novo. The karyotypes of the progenitors are usually normal, and the risk of recurrence is negligible (Alberman, Creasy, Elliot and Spicer, 1976). 65

66

C. Turieau et ai.: Kmyotypes of 413 couples with spontaneousabortions

Sato, 1968; Kadotani, Ohama and Sato, 1969; Wilson, 1969; de la Chapelle, Schrijder and Kokkonen, 1973; Kaosaar and Mikelsaar, 1973; Sinet, Dutrillaux, Prieur and Lejeune, 1973; Pemod, Soubirous and Robert, 1975; Battin, 1977; Byrd, Askew and McDonough, 1977; Kulazhenko, Levchenko, Usoev and Zhukova, 1977; Stenchever, Parks, Daines et al., 1977). We report here on a large series of 413 couples, and shall attempt to single out possible correlations between the types of chromosomal rearrangements, the history of fetal loss and the risk for further pregnancies.

Material

The population under study comprises 413 couples having experienced at least one spontaneous abortion. In every case both members of the couple were examined. An expulsion of the fetus before the sixth month was considered as a spontaneous abortion. Loss of the fetus after 6 mth was considered a stillbirth. Most spontaneous abortions occurred in the first trimester. In this paper the duration of pregnancies is given as from conception. Couples were referred for cytogenetic investigation by a variety of gynecologists and obstetricians. The age of the abortion, the state of the fetus, the possible existence of another cause for the abortion (i.e. uterine malformations, hormonal insufficiency, previously induced abortion(s)), are variable, According to their obstetrical history at the time of examination, couples can be assigned to one of 4 groups, defined as follows: (a) all pregnancies had ended in a spontaneous miscarriage; (b) there was at least one normal pregnancy besides one or more spontaneous miscarriages; (c) there was no normal child. All pregnancies were abnormal but the obstetric history included extrauterine pregnancies, hydatiform moles, stillbirths or early neonatal deaths (with or without evident malformations), as well as spontaneous miscarriages; (d) there were normal and abnormal pregnancies besides the miscarriages. Induced abortions were not included in the total

number of pregnancies. In cases of multiple marriages only the pregnancies of the couple under studjr were considered. Couples with spontaneous abortions ascertained in our laboratory because of the observation of a child (or a relative) with a chromosomal rearrangement were excluded. ‘Non-index’ couples, i.e. couples related to index couples, were also excluded. Control population

For obvious reasons - the size required in particular - it would have been practically impossible to constitute a correct control population. No normal adult population study exists that could be used as a control. The only available studies bear on newborn populations totalling almost 50,000 infants. Although they are not ideal controls of the present investigation, they are not significantly biased, since the control frequencies which are required concern balanced rearrangements having no deleterious effect. The control figures to be used in this study are those recently given by the Medical Research Council’s Committee on Protection against Ionizing Radiations (Evans, 1977).

Methods

Some 106 couples seen between 1968 and 1973 were routinely studied without applying banding techniques. If, however, a chromosomal rearrangement was found, this was further investigated by means of a banding technique. From 1973 on banding techniques were applied, and 307 couples were thus examined. Qtogenetic

techniques

R-banding was used routinely. When needed, G or C banding was also utilized. As a rule, for each person, some 16 mitoses were photographed and analyzed. Three or 4 of these were karyotyped. Definition of chromosomal rearrangements

Chromosomal rearrangements are, for the purpose of this study, divided into major and minor rearrangements.

61

C. Turleau et al.. Karyotypes of 413 couples with spontaneous abortions

These include: Major rearrangements. (a) Robertsonian translocations, which occur between two acrocentric chromosomes with breaks on opposite sides of the centromere in each chromosome and rejoining of the long arms. This results in the loss of one centromere and two short arms (which have no phenotypic effect) and reduction by one unit in chromosome number in the balanced heterozygote. (b) Reciprocal translocations, which result from the mutual exchange of chromosome segments between two non-homologous chromosomes. The heterozygote carrier has a fully balanced chromosome complement, with no reduction in chromosome number. (c) Inversions, which are due to two breaks in the same chromosome followed by reunion after inversion of the segment between the breaks. When this segment includes the centromere the inversion is called pericentric. If not, the inversion is paracentric. (d) Supernumerary fragments, which consist of a centromere and smalI arms. They are usually of unknown origin. We have retained only two Minor rearrangements. types of minor rearrangements: (a) A constitutional fragility of a particular chromosome site. This results in frequent breakages of this point. (b) Pericentric inversion of chromosome 9 limited to the heterochromatic region (inv(9)). polymorphisms, Polymorphisms. Chromosome which are largely a function of personal interpretation, have not been considered. They include: large satellites, large secondary constrictions, large Y chromosomes. Non-systematic anomalies (such as slight increase of chromosomal breakage, or occasional marker chromosomes) have also not been considered. Meiotic consequences

of chromosome

rearrangements

Major rearrangements have no phenotypic effect when they are in the balanced state. They are liable, however, to result in unbaianced gametes at meiosis through malsegregation. They may therefore be observed with an increased frequency in couples with reproduction failure. Rearrangements here considered as minor are also devoid of phenotypic effect. Their role during meiosis

is still poorly understood. They have been considered as possible factors enhancing nondisjunction through interchromosomal effect (Lejeune, 1963; Grell and Valencia , 1964).

Results

In the total 413 couples, 19 major and 6 minor rearrangements were found. There was no instance where both members of a couple had an abnormal karyotype. These rearrangements are detailed in Table I. A brief description of each affected family is given in the Appendix. TABLE I

Observed chromosomal rearrangements No. in laboratory registry

I. Major rearrangements

Robertsonian translocations 45,XX,t(lSq22q) 45,XYJWqGq) 45,XX,t(lSq2lq) 45,XY,Ql3q14q) 45,XX,t(13q14q) Reciprocal translocations 46,XX,t(2q+;3p-) 46,XX,t(S;l O)(ql 1 ;q3 1) 46,XX,t(l;2)@3;~2) 46,XX,t(8;13)(p12;q33) 46,XX,t(3;19)(p25;~12) 46,XY,t(1;19)(lql9p;lp19q) 46,XX,t(3;15)(q28;q22) 46,XX,t(l;l7)(p34;pll) 46,XY,t(7Q)(q3l;q21) Pericentric inversions 46,XX,inv(S)(p14q14) 46,XX,inv(3)(p14q12) 46,XX,inv(2)(pl2q14) Paracentric inversion 46,XX,inv(S)(ql2qlS) Supernumerary smaii metacentric 47,XX,+mar

4343 4435 6382 6958 8563 4288 4628 4838 6618 7428 7439 1714 8363 8199 6184 8055 8361 7367 7625

II. Minor rearrangements Constitutional breakage 46,XX,16q21 5053 46,XX,lOq24 7169 46,XX,17p12 7777 Pericentric inversion cf chromosome 9 46,XX,inv(9)(pllq13) 8252 46,XYjnv(9)(pllq13) 8341 46,XY ,inv(9)(pl lql3) 8913

C. Turleau et al.: Karyotypes of413 couples with spontaneousabortions

68 TABLE II

Comparison of the frequencies of balanced autosomal rearrangements in a population of 413 couples with spontaneous abortions and in the general population (The frequencies in the general population are from Evans (1977).) Total individuals examined

Robertsonian

43,558 826

Reciprocal translocations

Inversions

No.

%

No.

%

No.

%

36 9

0.08 1.09

6 3

0.01 0.36

81 17 ’

0.19 2.06

Total _-

D/D

Consecutive newborns Couples with spontaneous abortions Increase Significance (P)

translocations

DIG

No.

%

No.

%

31 2

0.07 0.24

8 3

0.02 0.36

x3 NS

xl8