R. K. Bhatt is a Consultant (Obstetrics and Gynecology and Fetal Maternal Medicine Splt), Army Hospital (Research and Referral, New Delhi). She is aluminous of B. J. Medical College, Pune, and obtained postgraduation from INHS Asvini, Mumbai. Her special interests are fetal medicine, genetics, invasive procedures and high-risk pregnancy. She has numerous publications to credit. She is currently working on preeclampsia screening.
Introduction :Recurrent pregnancy losses (RPLs) are seen in up to 15–20% of all clinically recognized pregnancies, 1–2% of women in general population. Repeated losses are seen in 5–10% of women. The prevalence of chromosomal rearrangements is 6.65% in couples with repeated pregnancy losses. Two to 4% of RPL are associated with parental balanced reciprocal and Robertsonian translocations.
Materials and Methods :The study was conducted at a tertiary care hospital in New Delhi, and in total, 204 couples with RPL enrolled in the study.
ResultsIn total, 4490 couples presented to the obstetric clinic, of which 204 (4.5%) couples had repeated pregnancy losses. Cytogenetic analysis was done in 198 couples. Out of total 198 patients, 14 patients (7.1%) had cytogenetic alterations. Most common aberrations observed were structural rearrangements, of which reciprocal translocations were more common. In our study cohort, all the couples had maternal age of ≤ 35 years and all the alterations were seen either in mother or in both parents.
Discussion: Our study highlights that cytogenetic alterations not only are common in first trimester miscarriages, but are an important event in miscarriages presenting at later period of gestation and in young mothers as well.
Keywords Robertsonian translocations · Balanced translocations · Unbalanced translocations · Miscarriage
Pregnancy loss is an enormous physical, social and emotional
burden on a couple which progresses to worry and
further discontent if pregnancy loss recurs. Recurrent pregnancy
losses are common and are seen in up to 15–20% of all clinically recognized pregnancies. Recurrent pregnancy
loss (RPL) is defined as “three or more consecutive
pregnancy losses prior to 20 weeks from the last menstrual
period” [1]. Successful pregnancy is dependent on multiple
factors including genetic and the reproductive tolerance of
the couples. When this tolerance is not achieved, it results in
the repetitive pregnancy loss with genetically incompatible
fetus. The prevalence of spontaneous pregnancy loss is 1–2%
of women in general population.
Repeated pregnancy losses are seen in 9–12% of women
aged < 35 years and increase to 50% after 40 years of age,
of which nearly 50% remain unexplained [2]. The risk of
miscarriage in subsequent pregnancies is 30% after two
losses, compared with 33% after three losses among patients
without a history of a live birth [3]. Two to 4% of RPLs
are associated with a parental balanced structural chromosome
rearrangement, most common of which are balanced
reciprocal and Robertsonian translocations. Others include
chromosomal inversions, insertions and mosaicism. These
abnormalities are responsible for unequal exchange of chromosome or genetic content during gametogenesis, leading
to partial deletions and duplication in the conceptus.
The prevalence of chromosomal rearrangements has
been found to be 2–8% in couples with repeated pregnancy
losses as compared to 0.55% of the general population [4].
The prevalence of chromosomal abnormality in product of
conception of miscarriage is found to be 50–70% [5] which
reemphasizes the need for comprehensive and systematic
cytogenetic workup of couples with RPL which remains an
uncommon practice till today.
The prevalence of cytogenetic alterations varies widely in
different studies. Most of the pregnancy losses during early
first trimester are attributed to chromosomal abnormalities
of which trisomies are the most frequently detected anomalies
(60–80%), followed by triploidies (12.4%), monosomy
X (7–20%), tetraploidies (9.2%) and structural chromosome
anomalies (4.7%) [5–7]. The mechanism for aneuploidies
is predominantly nondisjunction which may be related to
advanced maternal age, while structural abnormalities may
occur secondary to unequal chromosome segregation during
meiosis.
The study brings attention to unequivocal need for
cytogenetic workup to save couples from the guilt of being
incomplete as they cannot create a viable pregnancy as well
as for better understanding of disease biology.
The study was conducted at a tertiary care hospital in New
Delhi, India, from January 2016 to December 2018. In
total, 204 couples with RPL presented at obstetric clinic.
We reviewed the cytogenetics findings in all the couples
with history of repeated spontaneous miscarriage. Cytogenetic
analysis was offered to all the couples, for screening of
parental carrier abnormalities when other causes had been
ruled out, out of which 198 couples consented for cytogenetic
analysis.
A total of 198 couples were investigated for chromosomal
abnormalities with detailed case history of consecutive miscarriages
or stillbirth or previous history of malformed fetus
with multiple congenital malformations. The gestational age
at the time of pregnancy loss was estimated by reviewing
ultrasound. Parental karyotyping was performed to look for
chromosomal defects. Once a cytogenetic cause was found,
prenatal diagnosis was offered by amniocentesis and karyotyping.
Cytogenetic diagnosis was performed by culturing
of amniotic cells or by chorionic villi culture. Minimum 20
GTG-banded metaphase cells were karyotyped and analyzed
depending on availability of metaphases as per ISCN 2016.
In addition, total numbers of live births and subsequent miscarriages
are also being recorded. Dichotomous variables were analyzed using Chi-squared and Fisher’s exact test
(Table 1).
Statistical analysis of all the data set was performed using
Stata 14.0.
In total, 4490 couples presented to the obstetric clinic, of which 204 (4.5%) couples had repeated pregnancy losses. One hundred and ninety-eight couples consented for cytogenetic analysis. Cytogenetic analysis was done in all these couples. Out of total 198 patients (couples), 14 couples or their offsprings (7.1%) had cytogenetic alterations. Most common aberrations observed were structural rearrangements, of which reciprocal translocations were more common. In our study cohort, all the couples had maternal age of ≤ 35 years. Cytogenetic analysis revealed rearrangements in maternal genome in all the couples. In three couples, father also had cytogenetic alteration.
Reciprocal Translocations
Seven families (50%) had reciprocal translocation, of which six were carrier parents and one was child with de novo reciprocal translocation with normal karyotype in parents. Out of six carrier parents, five had children with normal phenotype of which four had normal genotype as well, while one had balanced translocation as was seen in mother. One of the six carrier parents had offspring with recombinant chromosomal rearrangement as 46,X_,rec(15) (15pter → 15q22::5p15 → pter)mat. One of the couples with normal child in this pregnancy had offspring with unbalanced translocation in previous pregnancy where the couple was counseled and termination was planned.
Robertsonian Translocations
Three out of 14 (21.4%) patients had Robertsonian translocations.
Chromosome 13 was involved in all of these cases,
two of which had involvement of chromosome 14 with chromosome
13 (66.7%), while one had fusion of chromosome
22 with chromosome 13 (33.3%). Among one of the couples,
father had additional chromosomal material on short arm
of chromosome 21. Children of all three couples delivered
phenotypically normal children, of which two had normal
genotype, while one had Robertsonian translocation same as
that seen in the mother. All three patients had phenotypically
normal children. However, one of these patients had similar
alteration as seen in the mother.
Unbalanced Translocation
Four families (28.5%) had unbalanced translocation with chromosomal gain or loss, out of which three couples had chromosomal alteration. Chromosomal analysis revealed that two of these three couples had chromosomal rearrangements in both the parents. One of the offsprings with karyotypically normal chromosomes had loss of 439 kb on 17p11.2 (Smith–Magenis syndrome). The couple had four previous miscarriages, including one with Pierre Robin syndrome and one with multiple congenital anomalies including congenital heart defects. The couple was counseled, and termination was planned. Two of the couples where both the parents had chromosomal rearrangements had normal phenotype and genotype in present offspring after previous 2–3 miscarriages. One patient, who presented with positivity for triple screen, was found to have balanced translocation in the offspring.
We, in India, have scarcity of data on prevalence and
spectrum of cytogenetic alteration in repeated pregnancy
losses. The study was carried out to bring increased
awareness of the genetic role in recurrent miscarriages.
Our study supports the previous finding of higher prevalence
of genetic alterations in couples with pregnancy
losses. Though it highlights that cytogenetic alterations
are common not only in first trimester miscarriages, they
are important in miscarriages presenting at later period of
gestation as well. We found higher frequency in second
and third trimester pregnancy losses as well.
In the present study, all the mothers presenting with
RPL were young (< 35 years), hence challenging the perception
of more prevalence of cytogenetic alterations with
higher maternal age.
Robertsonian translocations (ROBs) are the most common
structural abnormality in general population with
overall incidence of Robertsonian translocations of approx
1/1000 newborns [8, 9]. Though all human acrocentric
chromosomes are capable of participating in the formation
of Robertsonian translocations, chromosomes 13 and
14 are most commonly involved [10]. In those with RPL,
ROBs involving chromosomes 13 and 14 followed by 13
and 22 were reported to be more common [11]. Similar
findings were noted in our study as well. Homologous
ROBs are predominantly de novo in occurrence, while
heterologous ROBs are inherited from carrier parent [10,
12]. In our study as well, the heterologous ROB was inherited
from mother.
Reciprocal translocations were most common and were
seen 42.8% of couples (6/14) in our study. Some cytogenetic
derangements were noted. One child was found to
have reciprocal translocation where mother had increased
risk on triple screen (AFP, unconjugated estriol and beta
hCG) for Down syndrome which denotes false positivity,
further reemphasizing the need to carry out cytogenetic
studies and karyotyping in particular. The most commonly
involved chromosomes were chromosomes 5, 6, 10 and 15.
Reciprocal translocation of chromosomes 5 and 15 was
seen in two patients though at different band positions.
One of the offsprings in the couple showed recombinant
chromosome. Chromosome 6 had pericentric inversion
and translation with chromosome 1 in one patient each.
Chromosome 10 had reciprocal translocation with chromosomes
10 and 13 each. In the literature, reciprocal
translocations have been reported in approximately 50%
of patients [13]; similar prevalence was noted in our study
as well.
Unbalanced translocations were seen in 03 out of 14
patients (21.4%). In one of these, although both husband and
wife had cytogenetic rearrangement, the present offspring
had normal rearrangement. One couple was karyotypically
normal and had small deletion in offspring. It is little surprising
that individuals with microscopic unbalanced translocations
were presented with some abnormality. Couples
with unbalanced translocations found it difficult to conceive
than to have miscarriages. Scrutiny of the cases revealed
that one such case had heteromorphic variation of pericentric
inversion of chromosome 9, and the other two were the
presence of extrachromosomal material at short arm of acrocentric
chromosome.
Of the total 14 couples, nine (69.2%) couples had normal
outcome in subsequent pregnancies. Out of four couples,
whose subsequent pregnancies had cytogenetic alterations,
two had similar rearrangement as seen in one of the parents,
one had recombinant chromosome, while one was incidental
finding where chromosomal analysis was done because
mother was triple screen positive. One couple underwent
cytogenetic workup as previous product of conceptions
showed features suggestive of Pierre Robin syndrome and
another one had multiple congenital anomalies.
To conclude, structural cytogenetic rearrangements are
very common in couples with repeated pregnancy losses,
most common of which were found to be sporadic reciprocal
translocations in our study. For Robertsonian and sporadic
reciprocal translocations, karyotyping remains the procedure
of choice for chromosomal analysis. However, for submicroscopic
deletions or duplications, microarray is required
to be performed.
We recommend that all the patients with more than two
pregnancy losses at any period of gestation should undergo
routine parental cytogenetic analysis with karyotyping followed by microarray where clinical suspicion of involvement
of genetic factors is high. The challenge is to identify
the abnormality early to save the couple from agony
of pregnancy loss. Complete genetic workup will facilitate
appropriate genetic counseling to these couples.
Conflicts of interest There are no potential conflicts of interest to declare.
Human and Animal Rights Research involved human participants for
workup of miscarriages, and no animal trials were involved.
Informed Consent Written informed consent was obtained from all
the patients.
