Chromosome analysis of ectopic human conceptuses***

Chromosome analysis of ectopic human conceptuses SHERMAN ELIAS, M.D. MICHELLE LEBEAU, PH.D. JOE LEIGH SIMPSON. M.D. ALICE O. MARTIN, PH.D. Chicago, Illinois Maternal factors (e.g., salpingitis) are known to be associated with ectopic 9jtstations; however. few studies have considered the chromosomal complements or morphologic features of ectopic conceptuses. We studied 23 ectopic conceptuses remOVed from fat/Opian tubea during surgical resection. The chromosomal complements were normal (four with 46.XY; four wlth4$,XX) in all cases in which an intact embryo was identified. as well as In the single case charactari%ed by disorganized embryonic tissue. Ten of the 14 ectopic oo,nceptuses in whiCh only a gestational sac and placental villi were identified also showed normelctvomoaomal complements (seven with 46,XX; three with 46,Xy); in the remaining four cases, va/'lations val'lations from the. normal chromosomal complement were found (46.XXl47,XX. +9; 45.Xl46.XX; 46,XXl47,XX, +mar; and 92.XXXX). The former two probably signify underlying fetal abnormalities; however. the latlel"two could have reflected. respectively, in vitro aberrations or tetraploidy characteristic of normal amnion. Pooled data from this study and two previous reports indicate that ectopic conceptuses probably have no higher frequency of chromosomal abnormalities than inc utero conceptuses of comparable embryonic ages. (AM. J. OeSTET. GVNECOL. 141:698, 1981.)

ECTOPIC PREGNANCY (eccyesis) refers to implantation of the zygote outside the uterus or in an abnormal location within the uterus. The frequency of ectopic pregnancies compared to intrauterine pregnancies has been estimated between 1: 84 and 1: 230. 1• 2 By far the most common ectopic location (approximately 95%) is the fallopian tube. 3 Factors commonly implicated in the pathogenesis of ectopic pregnancies include: (1) acute and chronic scalpingitis, (2) congenital abnormalities of the fallopian tube, (3) previous surgical procedures on the fallopian tube, (4) endometriosis, (5) transmiFrom the Section of Human Genetics, Department of Obstetrics and Gynecology, Northwestern University Medical School. Investigation by the authors was supported by Grants HD 11021, HD02841, and HD 08255 from the National Institutes of H eaith. In addition, investigation by Dr. Elias was aided by Basil O'Connor Starter Research Grant No. 5-306 from the March of Dimes Birth Defects Foundation and by a grant from the W. K. Kellogg Foundation. Presented at the Twenty-eighth Annual Meeting of the Society for Gynecologic Investigation, St. Louis, Missouri, March 19-21,1981. Reprint requests: Sherman Elias, M.D., Section of Human Genetics, Northwestern University Medical School, Prentice Women's Hospital and Maternity Center, 333 East Superior St., Chicago, Illinois 60611.

698

gration of the ovum from one ovarythroughthe abdominal cavity into the contralateral f~llopian tube with resultant ectopic nidation, (6) tumors that distort the fallopian tube as result oftheir location, (7) retrogmde menstrual flow into the fallopian tube such that normal migration is impeded, and (8) the presence oLan intrauterine contraceptive device. Another possible factor, less commonly considered, is that the conceptus is morphologically abnormal and predisposed toward ec~ topic nidation because of delayed migration. Among factors which could predispose toward such morphomorphQlogic aberrations are chromosomaLabnormalities. If ectopic conceptuses showed cytogenetic abnormalities, the observation would have important clinkalimplications, specifically in reference to genetic counseling and prenatal diagnosis. For these reasons we investigated the cytogenetic complements and gross morphologic features of conceptuses removed from the fallopian tube during surgical resection. Material and methods Patient selection and spec~n . coUectK!n. coUecti
©

1981 The C. V. Mosby Co.

Volume 141 Volume 141 Number 6 Number 6

Hospital and Hospital and Maternity Maternity Center, Center, Northwestern Northwestern UniverUniversity. The sity. The only only preselection preselection criterion criterion was was the the exclusion exclusion of specimens of specimens from from women women who who had had previously previously underundergone fallopian gone fallopian tube tube reconstructive reconstructive operation. operation. In In most most cases one cases one of of the the physician physician investigators investigators (S. (S. E. E. or or J. J. L. L. S.) S.) was present was present in in the the operating operating room room to to collect collect and and idenidentify the tify the specimen. specimen. If If attendance attendance was was not not possible, possible, the the operating surgeon operating surgeon was was instructed instructed in in the the method method of of specimen collection. specimen collection. Specifically, Specifically, each each fallopian fallopian tube tube was first was first opened opened longitudinally. longitudinally. The The products products of of conconception were ception were dissected dissected free free and and then then transferred transferred to to aa sterile glass sterile glass screw-cap screw-cap bottle bottle containing containing Hanks Hanks balbalanced salt anced salt solution solution without without magnesium magnesium and and calcium calcium (Flow Laboratories, (Flow Laboratories, McLean, McLean, Virginia) Virginia) but but supplesupplemented with mented with penicillin penicillin (100 (100 U U II m!) m!) and and streptomycin streptomycin sulfate (50 sulfate (50 mcg/ml). mcg/ml). Specimens Specimens were were either either transtransported directly ported directly to to our our laboratory laboratory or or kept kept refrigerated refrigerated before being before being transported transported the the next next working working day. day. Clinical information. Clinical information. As As noted, noted, one one of of the the invesinvestigators (S. tigators (S. E. E. or or J. J. L. L. S.) S.) attempted attempted to to be be in in the the operatoperating room ing room in in order order to to examine examine the the fallopian fallopian tubes tubes and and other pelvic other pelvic structures structures for for overt overt evidence evidence suggesting suggesting pelvic inflammatory pelvic inflammatory disease disease or or other other pelvic pelvic abnorabnormalities. In malities. In other other cases, cases, the the surgeon surgeon was was contacted contacted to to elicit such elicit such information. information. Additional Additional clinical clinical data data were were obtained either obtained either by by patient patient interviews interviews or or by by review review of of the medical the medical records records and and by by review review of of operative operative reports. reports. reports describing describing extirpated extirpated specispeciFinally, pathology Finally, pathology reports mens (i.e., mens (i.e., fallopian fallopian tubes tubes and and products products of of conception) conception) were reviewed. were reviewed. Morphologic evaluation Morphologic evaluation of of ectopic ectopic conceptuses. conceptuses. Upon being Upon being brought brought to to our our laboratory laboratory each each ectopic ectopic conceptus specimen conceptus specimen was was inspected inspected by by one one investigator investigator (S. E.). (S. E.). Each Each specimen specimen was was classified classified into into one one of of two two categories: (1) categories: (1) specimens specimens with with an an identifiable identifiable embryo embryo and (2) and (2) specimens specimens consisting consisting of of only only aa gestational gestational sac sac (intact or (intact or fragmented) fragmented) and and placental placental villi. villi. Cytogenetic laboratory Cytogenetic laboratory procedures. procedures. All All ectopic ectopic conconceptus specimens ceptus specimens were were transferred transferred to to sterile sterile Petri Petri containing Hanks Hanks balanced balanced salt salt solution solution (HBSS) (HBSS) dishes containing dishes without magnesium without magnesium and and calcium calcium (Flow (Flow Laboratories, Laboratories, McLean, Virginia) McLean, Virginia) but but supplemented supplemented with with penicillin penicillin (100 U/ml) U/ml) and (100 and streptomycin streptomycin sulfate sulfate (50 (50 mcg/ml) warmed to warmed to 37° 37° C. C. If If so so identified, identified, embryonic embryonic tissue tissue was was utilized to utilized to initiate initiate cell cell culture; culture; otherwise, otherwise, gestational gestational membranes or membranes or placental placental villi villi were were utilized. utilized. Regardless Regardless of source, of source, specimens specimens were were rinsed rinsed two two to to four four times times with with HBSS and HBSS and antibiotics, antibiotics, followed followed by by two two additional additional rinses rinses with Ham's with Ham's F-12 F-12 media media with with glutamine glutamine (Grand (Grand Island Island Biological Company, Biological Company, Grand Grand Island, Island, New New York) York) supsupplemented with plemented with 15% 15% fetal fetal bovine bovine serum, serum, 100 100 U/ml of of penicillin, and penicillin, and 50 50 mcg/ml of of streptomycin streptomycin sulfate. sulfate. Specimens were Specimens were minced minced with with surgical surgical scissors, scissors, and and the the

Chromos()me analysis Chromos()me analysis of of ectopic ectopic conceptuses conceptuses

699 699

pieces of pieces of tissue tissue were were seeded seeded into into tissue tissue culture culture flasks. flasks. Depending upon Depending upon the the amount amount of of tissue tissue available, available, two, two, three, or three, or four four cultures cultures were were initiated initiated from from each each ectopic ectopic conceptus. Cultures conceptus. Cultures were were provided provided the the above-menabove-mentioned growth growth media, media, gassed gassed with with ,I)o/c ,I)o/c carbon carbon dioxide dioxide II tioned 95% balanced 95% balanced air air and and maintained maintained at at 37° 37° C C in in aa humidhumidified incubator. ified incubator. The The pH pH of of the the medium medium was was maintained maintained between between 7.2 7.2 and and 7.4 7.4 and and the the growth growth medium medium was was exexchanged weekly. changed weekly. Subcultures Subcultures were were prepared prepared by by (I) (I) disdissociating confluent sociating confluent cells cells from from the the growth growth surface surface of of the the flasks by flasks by addition addition of of proteolytic proteolytic enzymes enzymes (0.05% (0.05% tryptrypand 0.02<;t 0.02o/c elhylenediaminetetraacetate elhylenediaminetetraacetate in in HBSS, HBSS, sin sin and calcium and calcium and magnesium magnesium free; free; Grand Grand Island Island Biological Biological Company) and Company) and (~!) reinoculating reinoculating cells cells into into three three fresh fresh culture flasks culture flasks (U\ (U\ split). split). If If needed, needed, additional additional subculsubcultures were tures were prepared prepared weekly weekly thereafter. thereafter. All cytogenetic All cytogenetic studies studies were were performed performed with with subculsubcultured fibroblasts tured fibroblasts from from the the first first or or second second passage. passage. CulCultures in tures in the the log log phase phase of of growth growth were were exposed exposed to to ColColcemid cemid (Grand (Grand Island Island Biological Biological Company) Company) at at aa final final concentration concentration 0.1 0.1 mcg/ml for for 2 2 hours hours to to accumulate accumulate after which which cell cell suspensions suspensions were were cells in cells in metaphase, metaphase, after prepared by prepared by exposure exposure to to proteolytic proteolytic enzymes enzymes as as alalready described. ready described. Cells Cells in in suspension suspension were were then then treated treated with hypotonic with hypotonic potassium potassium chloride chloride (75 (75 mM) mM) prior prior to to being fixed being fixed with with 3: 3: II methanol: methanol: glacial glacial acetic acetic acid. acid. Trypsin-giemsa banding Trypsin-giemsa banding (GTG) (GTG) was was achie\ed achie\ed by by modmodof the the Seabright Seabright 44 method. method. If If possible, possible, metametaification of ification phases were phases were selected selected for for analysis analysis from from at at least least two two culcultures tures initiated initiated from from each each specimen. specimen. At At least least 12 12 metametaphases were phases were analyzed analyzed from from each each ectopic ectopic specimen. specimen.

Results Clinical data. Clinical data. Table Table II summarizes summarizes the the pertinent pertinent clinclinical data ical data regarding regarding the the 23 23 women women from from whom whom ectopic ectopic conceptuses were conceptuses were obtained. obtained. Their Their mean mean age age was was 25.8 25.8 years (range, years (range, 17 17 to to 39 39 years). years). Fourteen Fourteen of of these these 23 23 women had women had at at least least one one previous previous live live birth. birth. Six Six of of the the 23 women 23 women had had experienced experienced one one or or more more spontaneous spontaneous abortions (all abortions (all first first trimester); trimester); one one patient patient (Case (Case No. No. 20) 20) had a previous ectopic pregnancy in the contralateral fallopian tube. fallopian tube. In In two two patients patients (Cases (Cases ;\los. ;\los. II II and and 15) IS) intrauterine contraceptive intrauterine contraceptive devices devices were were present present within within the uterine the uterine cavity cavity at at the the time time of of operation. operation. In In Case Case No. No. 16 16 bilateral bilateral Pomeroy Pomeroy tubal tubal ligation ligation had had been been performed. performed. Observations at Observations at operation operation and and pathologic pathologic studies studies showed chronic showed chronic inflammation inflammation involving involving the the extirpated extirpated fallopian tube fallopian tube in in seven seven of of 23 23 cases cases (Nos. (Nos. 1, 1, 3, 3, 7, 7, 11, 11, 13, 13, 16, 16, and and 19). 19). Such Such histopathologic histopathologic evidence evidence consisted consisted of of chronic salpingitis, chronic salpingitis, chronic chronic interstitial interstitial salpingitis, salpingitis, folfollicular salpingitis, licular salpingitis, or or salpingitis salpingitis isthmica isthmica nodosa. nodosa. In eight In eight cases cases (Nos. (Nos. 2,11,12, 2, II, 12, 15, IS, 16.17.IR,and22) 16.17.IR,and22)

700 Elias at al.

November 15. 1981 Am. J. Obstet. Gynecol.

Table I. Clinical information regarding the 23 women from whom ectopic conceptuses were recovered Gravidity Case Age (includes present No. (yr) ectopic pregnancy) 1 2 3 4 5 6 7 8 9 10

4 1 5 3 1 1 1 3 3

11

28 31 35 33 25 23 17 28 19 24 20

12 13 14 15

33 39 30 30

2 4 2 3

16

36

17 18

Parity (>20 weeks)

No. offirsttrimester spontaneous Last menstrual Date of abortions operation Period 1 0 1 0 0 0 0 0 0

Pathologic evidence of chronic salpingitis·

0

7/12179 6/28179 7128179 9/18179 8115179 9/13179 9/18179 10/15/79 911179 11119179 10/15179

8/16179 8/19179 9/18179 10/13179 11112179 11112/79 11124179 12/5179 12/6179 12117179

Present Absent Present Absent Absent Absent Present Absent Absent Absent Present

1 2 1 1

0 1 0 1

12/15179 1112/80 1130/80 2/22/80

12/27179 3/16180 3/26180 3/26/80

Absent Present Absent Absent

5

4

0

3/5180

5/19/80

Present

28 34

1 5

0 2

0 2

3/23/80 5/10/80

5/28180 6117/80

Absent Absent

19 20

28 24

3 3

2 0

0 2

3/15180 6/13/80

6127180 8/5180

Present Absent

21 22 23

33 30 28

6 1 1

1 0 0

4 0 0

9/17/80 11114/80 12/1180

1115180 116181 1116/81

Absent Absent Absent

2 0 3 2 0 0 0 2 2

2

Other pertinentinfOTmlliion

Intrauterine contraceptive device in situ Previous trisomy 13 offspring Intrauterine contraceptive device in utero Rilateralpomeroy tubal ligation. 1977 Previous elective firsttrimester abortion Previous ectopic pregnancy in contralateral fallopiantllbe

*Review of pathology report indicated the presence of a chronic inflammatory process of the fallopian tube on the basis o(ilistopathologic diagnosis of chronic salpingitis. chronic interstitial salpingitis, follicular salpingitis, or salpingitiS isthmica nodosa.

an intact embryo (20 to 35 mm) was found; none of these eight showed external malformations. In one additional case (No.6) embryonic tissue appeared disorganized and lacked identifiable structures; however, striated muscle and skin were observed through an inverted microscope (x 40). In the remaining 16 cases no identifiable embryo was identified, merely an empty or fragmented gestational sac and placental villi. Cytogenetics. In 18 of 23 cases more than one culture was analyzed. In the remaining five cases failure of some cultures to grow necessitated analyses on the basis of only a single culture. The chromosomal complements were normal (four with 46,XY; four with 46,XX) in all eight cases in which an intact embryo was identified, as well as in the case characterized by disorganized embryonic tissue ( 46,XX). Ten of the 14 ectopic conceptuses in which only gestational sac and placental villi were identified also showed normal chromosomal complements (seven with 46,XX; three with 46,XY). In the remaining four cases derived from gestational sac and placental villi, variations from the normal chromosomal complement were found

(Table II). In Case No.5, among IS cells analyzed from the single culture available, four showed tetraploidy (92,XXXX); the other 11 cells appeared to be hypomodal tetraploid cells with chromosome counts raqg;. ing from 50 to 90. In three cases mosaicism that included a normal 46,XX line was detected. In Case No. 8, 46,XX/47,XX,+9 mosaicism was found inaH three cultures available for analysis. Among a total of 19 cells analyzed, six showed trisomy 9. In Case No. 14,among 50 cells analyzed from the only available culture, three were 45,X and 41 were 46,XX, suggesting 45,X/46,XX mosaicism. (The remaining six cells were hypotnod~J, missing various different chromosomes other than X); InCase No. 21, among 41 cells analyzed from the ()nly available culture, three cells showed a marker chromosome (Fig. 1). The marker chromosome, an acrocentric approximately l4 the size of chromosomes Nos. 2Land 22, was always observed in close proximity to D- or G-group chromosomes. C banding showed a positive heterochromatic region, suggesting presenceofa centromere. The origin of this marker chromosome could not be further identified.

Chromosome analysis of ectopic conceptuses 701

Volume 141 Number 6

Fig. 1. Case No. 21. Ectopic conceptus with a 46,XX/47,XX,+mar complement. Left: Partial metaphase preparation with arrow directed toward the marker chromosome. Trypsin-giemsa banding (GTG). Right: Sequential C banding (CBG) of the same partial metaphast! showing a positive heterochromatic region in the marker chromosome, suggesting the presence of a centromere.

Table H. Cytogenetic studies of ectopic conceptuses in which variations from the normal chromosomal complement were observed. Source of tissue in each case was gestational sac and placental villi

Total ceU

Case No.

metoplwes aMiyzed

5 8 14 21

15 19 50 41

No. of cultures from which cytogenetic studies were Performed* 1 3

1 1

45 1 45, Other

2

4:j:

1#

2**

6~

Chromosomes per ceU

J 1 45,}(

3

46, Other 3§

1 46,xx J47,xX,+9 147,xx,+-1 7 41 36

~5(j:s;90 llt

!92,xx

4

2

*In all cases four cultures were initiated from each ectopic conceptus; however, some cultures either failed to grow or did not yield metaphase preparations suitable for analysis. tBroken tetraploid cells with chromosome numbers ranging from 50 to 90. :j:One 45,XX, -18; one 45.XX, -16; one 45.XX, -18; one 45.XX with missing chromosome undetermined. lOne 46,XX.+9,-21; one 46,+9,-16; one 46,XX,+9,-12 (each cell from a different culture). /lOne 47,XX,+9 cell found in each of the three cultures. ~Two 45,XX,-16; one 45,XX,-7; one 45,XX,-14; one 45,XX,-20; one 45,XX,-C group chromosome. #One 45,XX,-2,-20, +mar. *·One 45,XX,-21; one 45,XX,-13.

Comment In the present study four of the 23 ectopic conceptuses showed variations from the normal chromosomal complement, but their interpretations must be approached cautiously. In three of the four cases mosaicism that included a normal 46,XX cell line was de-

tected. In Case No.8, 46,XXI47,XX,+9wasdetected in three different cultures, strongly indicating that a trisomy 9 ce1l1int~ was actually present. In fa.ct, trisomy 9 has been detected among first~trimesterspontanrous abortuses as well as more rarely among live born malformed children,'" 6 Moreover, trisomy 9 in live births is

702 Elias et al.

November 15. 1981 Am. ]. Obstet. Gynewl.

Table III. Cytogenetic findings among reported series of ectopic conceptuses Variationsfrorn nonruJl ~omt:d complement

Ntmnal

chTtnMSOmal Stries

No.

t?f

cases

c~t

Tltraploid

46XX . 146,x¥

No.

Busch and Benirschke10 (1974)

25

13

8

Poland et al. l l (1976)

16

6

6*

Present series

23

12

7

Total

64

31

21

2

3

AYi8U,f>loiti No·1

T,pe

2 1 1 1 1 1 1 8

45,X/46.XX 47,XY,+G 46,XXl47,XX,+D 47,XY,+21 47.XX,+16 45.Xl46.XX 46.X'Cl47 ,XX, +9

Other No·1

Type

46,XX/47,XX, + mar

Tetraploid cells may be of amnionic origin. hence they are considered separilte1y. The marker chromosome may haveoriginilted either from the amnion or as an in vitro culture aberration; hence it is considered separately. *lncludes one specimen considered a 46,XY;del (16)(q22) by the authors. In our opinion this purponedabnormality represents a normal variant of chromosome No. 16.

usually associated with mosaicism involving a normal diploid cell line. In a second case (No. 14) three of 50 (6%) cells showed monosomy X, suggesting 45,X/ 46,XX mosaicism. However, the possibility that cells from a nonmosaic 45,X ectopic conceptus became admixed with 46,XX cells of maternal origin could not be excluded. Indeed, such spurious mosaicism seems especially plausible in view of knowledge that about 24% of chromosomally abnormal spontaneous abortuses are 45,X.6 In a third case (No. 21), three of 41 cells analyzed from the single available culture showed an extra marker chromosome (47,XX,+mar). A "marker" chromosome may be defined as a morphologically distinguishable chromosome that cannot be more definitively characterized. The significance of supernumerary marker chromosomes is uncertain, and they may originate from any chromosome(s) in the complement. To determine the significance of a marker chromosome present in a minority of cells, multiple cultures should ideally be analyzed. Presence of the marker chromosome in only a single culture suggest in vitro aberration, not reflecting an underlying embryonic abnormality. Unfortunately, in this case only one culture was available; thus, uncertainty remains concerning the significance of the marker chromosome. However. mosaicism involving marker chromosomes in cultured amniotic fluid cells is usually not confirmed in fetuses or infants; thus, most likely the marker chromosome did not originate in the ectopic conceptus but rather originated in vitro. In a fourth case (No.5) all 15 cells from the sole available culture showed tetraploidy (92,XXXX). Tetraploidy occurs among spontaneous abortuses, and several live born infants have been tetraploid. 6. 7 However, more commonly tetraploidy is an ostensibly normal finding in amniotic fluid cells derived from a

pregnancy in which a fetus shows a normal diploid complement.B Furthermore, X-chromatin studies and DNA determinations indicate that tetraploid celisoccut naturally in human amnion. 9 In addition, in this case the cultured ectopic conceptus material was derived from gestational sac and placental villi. Thus, tetraploidy in the embryo cannot be established witheertainty, and in fact it seems more reasonable to assume that the tetraploid cells reflect not etnbryonicbut rather amnionic origin. In Table III available cytogenetic data cOncetnihg studies of ectopic pregnancies are presented. Unfortunately, no specific details were given regarding selection criteria in either of these two previous studies,ro• 11 and chromosome banding techniques were notu/iedin one study .10 Thus, comparisons between previous studies and the present series may be difficult. Nonetheless, eight of the pooled total of 64 ectopic conceptuses (12.5%) showed a probable chromosomal abnormality. Five of these eight abnormal ectopic conceptuses showed autosomal trisomy (including two withmosa, icism involving a 46,XX cell line), whereasthreeconceptuses had 45,X/46,XX mosaicism. If the three CMes with tetraploidy and the one case with a markerchromosome are assumed to reflect true cytogeneticabnormalities in the conceptuses, the frequency ofchromosomal abnormalities among ectopic conceptuses would be even higher, i.e., 11/64 (19%). Is the frequency of chromosomal abnormalities among ectopic conceptuses different from that of intrauterine pregnancies? Unfortunately, the issue -can only be addressed in an inferential fashion. Hertig and associates 12 conducted morphologic studies ofeady implanted embryos recovered at the time ofhysterectomy and concluded that six of 26 (23%) showedabnormalities incompatible with continued embryogene-

Volume 141 Number 6

sis; however, the chromosomal complements of these abnormal conceptuses are unknown. Other studies have assessed the frequency of chromosomal abnormalities in either spontaneous abortions (50% to 60%)13 or induced abortions (7%)14, 15; these abortuses were usually collected at least 8 weeks after the first missed menstrual period, or 6 weeks' embryonic age. Such series contained few abortuses less than 6 weeks' embryonic age. On the other hand, most ectopic conceptuses are surgically removed at only 2 to 6 weeks' embryonic age. Thus, direct comparisons between ectopic gestations and in utero gestations (i.e., induced or spontaneous abortuses) with respect to chromosomal abnormalities cannot readily be made. However, among a series of 955 induced abortions, Yamamoto and associates 14• 15 performed cytogenetic studies of 84 abortuses said to be at 4 to 5 weeks' embryonic age. Nine of the 84 (14%) showed chromosomal abnormalities. The frequency of chromosomal abnormalities in 2- to 5-week intrauterine conceptuses (4 to 7 weeks from the first missed menses) can thus be estimated to be 14% to 23% .12, 14. 15 Such estimates permit at least rough comparisons of the frequency of chromosomal abnormalities between in utero and ectopic conceptuses at

REFERENCES 1. Harralson,]. D., Van Nagell,J. R., and Roddick,]. W.,Jr.: Operative management of ruptured tubal pregnancy, AM. j. OBSTET. GVNECOL. 115:995, 1973. 2. Clark, j. F. S., and Jones, S. A.: Advanced ectopic pregnancy, j. Reprod. Med. 14:30, 1975. 3. Brenner, P. F., Roy, S., and Mishell, D. R., Jr.: Ectopic pregnancy: A study of 300 surgically treated cases,JAMA 20:673, 1980. 4. Seabright, M.: A rapid banding technique for human chromosomes, Lancet 2:971, 1971. 5. Rethore, M.: Syndromes involving chromosomes 4, 9, and 12, in Yunis, J. j., editor: New Chromosomal Syndromes; New York, 1977, Academic Press, Inc., p. 119. 6. Hassold, T., Chen, N., Funkhouser,J., Jooss, T., Manuel, B., Matsuura,j., Wilson, C., Yamane,j. A., and Jacobs, P. A.: A cytogenetic study of 1000 spontaneous abortions, Ann. Hum. Genet. 44:151,1980. 7. Golbus, M. S., Bachman, R., Wiltse, S., and Hall, B. D.: Case report: Tetraploidy in a liveborn infant, j. Med. Genet. 25:329, 1976. 8. Milunsky, A.: Genetic Disorders and the Fetus. Diagnosis, prevention, and treatment, New York, 1979, Plenum Press, p. 24. 9. Klinger, H. P., and Schwarzacher, H. G.: The sex chromatin and heterochromatin bodies in human diploid and polyploid nuclei, J. Biophys. Biochem.Cytol. 8:345, 1960.

Chromosome analysis of ectopic conceptuses

703

comparableembr'fonic ages. Even in the highly unlikely event that all 12 abnormal chromosomal complements found among the 64 ectopic conceptuses (19%) (Table II) truly reflect embryonic chromosomal abnormalities, ectopic conceptuses still show no higher frequency of chromosomal abnormalities than in utero conceptuses of comparable gc:~stational age. This especially seems true if one accepts the likely assumption that only eight of 64 (12.5%) ectopic conceptuses were chromosomally abnormal. On the basis of our studies, we conclude that ectopic conceptuses are no more likely to show chromosomal abnormalities than in utero conceptuses of comparable gestational age. Accordingly, maternal factors (e.g., chronic salpingitis, endometriosis, etc.) remain the likely explanation for most ectopic pregnancies. Finally, our findings are applicable to genetic counseling. Ectopic pregnandes can be assumed to have no higher frequency of chromosomal abnormalities than induced abortions and less than spontaneous abortuses. Even repeated ectopic gestations probably do not place a woman at increased risk for recurrent aneuploidy, unlike the situation that occurs following repeated abortions.16. 17

10. Busch, D. H., and Benirschke, K.: Cytogenetic studies of ectopic pregnancies. Virchows Arch. (Cell PathoL) 16: 331, 1974. 11. Poland, B. J., DiU, F. J., and Styblo, C.: Embryonic development in ectopic human pregnancy. Teratology 14:315, 1976. 12. Hertig, A. T., Rock,j., Adams, E. C., and Menkin, M. C.: Thirty-four fertilized human ova, good, bad and indifferent recovered from 210 women of unknown fertility. A study of biologic wastage in early human pregnancy, Pediatrics U:202, 1959. 13. Carr, D. H., and Gedeon, M.: Population cytogenetics of human abortusc!S, in Hook, E. B., and P()Jter, 1. H., editors: Population cytogenetics: Studies in humans, New York, 1977, Academic Press, Inc., p. 1. 14. Yamamoto, M., Fujimori, R., Ito, T., Kamimura, K.,and Watanabe, G.: Chromosome studies in 500 induced abortions, HutrumgenetikH:9, 1975. 15. Yamamoto, M., Ito, T., and Watanabe, G.: fine Weitere Chromosomenanlyse bei kiinstlichen Aborten, Hum. Genet. 34:69, 1976. 16. Elias, S., and Simpson,j. L.: Evaluation and clinical man· agementof patumts at apparent increased risk for spontaneous abortions, in Porter, 1. H., and Hook, E. B., editors: Human Embryonic and Fetal Death, New York, 1980, Academic Press, Inc., p. 331. 17. Simpson, J. L.: Repeated suboptimal pregnancy outcome, Birth Defects 17(1):1l3, 1981.