Results:
From January 2014 to June 2019, 1243 pregnant women between
24+0 and 39+4 gestational weeks
underwent late amniocentesis in our hospital. They carried 1272 fetuses
including 1154 singleton pregnancies, 5 monochorionic pregnancies with
single puncture (monochorionic monoamniotic, MCMA), 44 monochorionic
pregnancies with double puncture (monochorionic diamniotic, MCDA), 36
dichorionic twin pregnancies with double puncture (dichorionic
diamniotic, DCDA) and 2 triplet pregnancies with triple punctures
(trichorionic triamniotic, TCTA). Among them, 7 MCDA and 5 DCDA chose to
conduct amniocentesis on the fetuses with abnormal ultrasound finding;
24 MCDA, 11 DCDA and 2 TCTA chose to conduct amniocentesis on the
healthy fetuses because the abnormal ones had been terminated already.IndicationsTable 1 showed the late amniocentesis indications among women studied.
It was observed that the most common cause was late detected aberrant
ultrasound findings (or a combination of ultrasound findings with other
earlier indications) (1123/1272 fetuses, 88.3%). These abnormal
ultrasound findings included Central nervous system anomalies (183/1272,
14.4%), cardiovascular defects (161/1272, 12.7%) and urinogenital
defects (157/1272, 12.3%). Another common cause of late amniocentesis
was suspected prenatal diagnosis results (113/1272 fetuses, 8.9%).
Other causes were advanced maternal age, abnormal childbearing history
and monogenic disease in the family.ComplicationsCommon complications of
amniocentesis
include
chorioamnionitis,
preterm
birth (PTB),
intra-uterine
demise (IUD) and trauma 12. In our study, only one
chorioamnionitis was identified on the third day following the
amniocentesis.
A total of 38 PTBs (38/1243, 3.1%)
and 21 IUDs (21/1272, 1.7%) were identified in our study. Among these
PTB and IUD cases, 6 PTBs (15.8%) and 4 IUDs (19%) developed within
the first week
after
amniocentesis. 8 PTBs (21.1%) and 5 IUDs (23.8%) developed within one
month but before 37 gestational weeks after amniocentesis. The remaining
PTBs (63.2%) and IUDs (57.1%) cases took place after one month of the
amniocentesis. 89.7% (104/116) complication is associated with fetal
abnormalities, and 7.8% (9/116) complication took place in fetuses with
suspected prenatal screening tests. (Table S1)
PTBs occurred in 0.3% (4/1155) and 0.5% (6/1155) in singleton
pregnancies, while that occurred in 2.4% (2/84) and 2.4% (2/84) in
twin pregnancies (one week and one-month post-procedure, respectively).
No PTB was observed in triplet pregnancies. The earliest PTB occurred in
a singleton pregnancy at the third day after the operation. 89.5% PTBs
(34/38) took place in fetuses with ultrasound anomalies. Near one-third
(12/38,31.6%) of PTBs among our cases happened to twin pregnancies, as
twin pregnancies are faced with a higher risk (56.6%) for PTB than
singleton pregnancies (9.7 %) even without late
amniocentesis13. Of note,
all
12 twin pregnancies suffering PTBs have double punctures, including 8
MCDA and 4 DCDA.
For IUD, it took place in 1.1% (13/1154) singleton pregnancies and
5.9% (5/85) twin pregnancies. No IUD was observed in triplet
pregnancies. The earliest IUD occurred in a singleton pregnancy with CNS
anomalies on the next day after the operation. Only one of the 21 IUDs
cases reported no fetal malformations and all 5 twin pregnancies
suffering IUD have double punctures. It should be noted that among 5 IUD
cases in twin pregnancies, 2 cases show 50% mortality rate, with one
case having oligohydramnios and the other with hydramnios.Pathogenic findingsCMAIn our cohort, chromosomal disorders
were identified in 133 (133/1272, 10.5%) fetuses. Sixty-six of them
were aneuploidies (66/1272, 5.2%), including 35 trisomy 21, 9 trisomy
18 and 6 trisomy 13. Other aneuploidies included sex chromosomal
abnormality (like XXX, XXY), trisomy 8 and trisomy 9. (Table S2)
Pathogenic
copy
number abnormality were identified in 67 (67/1272, 5.3%)
fetuses
by CMA, while only two could be detected by karyotyping (a deletion of
on chr18q22.3q2314 and a duplication of on
5q21.1q22.2). The other 24 CNVs
(24/26, 92.3%),
two trisomy 21 and one trisomy 18
from CMA could not be identified via
karyotyping.ES (MES and WES)MES and WES were carried out in five and seven fetuses (parents and
fetus) respectively.
Chromosomal disorders were identified in one fetus (1/12, 8.3%) whose
CMA result was negative. Two copy number changes were considered likely
pathogenic (2/12, 16.7%), while another two cases were likely benign
(2/12, 16.7%).
However, 6 cases tested by exome sequencing showed different genetic
results compared with tests by CMA.
4 cases tested by exome sequencing
(1 case with pathogenic result, 2 cases with likely pathogenic result
and 1 with likely benign result) were reported positive by CMA. 2 cases
tested by exome sequencing (1 case positive and 1 likely benign) were
reported aneuploidies by CMA. (Table 2)
Two ES reports were supported by the ultrasound findings. In the first
case, the pregnant woman with pathogenic WES findings underwent
amniocentesis due to FGR identified by ultrasound. Trio-exome sequencing
showed a mutation c.625+1G>A in the SLC7A7 gene compatible
with fetal Lysinuric protein intolerance (LPI) 15. The
couple chose to continue the pregnancy, but IUD took place 2 months
after the amniocentesis. In the second case, the couple was referred for
genetic counseling during their fourth pregnancy due to fetal
cenencephalocele, hydrocephalus and cerebellum dysplasia. They decided
to terminate the pregnancy, although CMA showed normal result. The
muscle tissue of the aborted fetus was then isolated for WES. ISPD gene
mutations, c.674delC(p.A225Dfs*21) and c.1106T>G(p.V369G),
associated with Walker-Warburg syndrome were identified16 which was consistent with the ultrasound findings
Pregnancy outcomeIn our cohort, 725 (57.0%) pregnancies resulted in
live
births, 451 (35.5%) pregnancies were terminated, 21 (1.7%) fetuses
died in utero, and 75 (5.9%) fetuses were lost to follow up. (Table 3)
Among the 451 terminated pregnancies, pathogenic gene was identified in
114 cases by one of CMA and ES (114/132, 86.4%). 310
couples
terminated the pregnancy despite normal results of CMA and ES
(310/1272, 24.4%) owing to
the
fetal abnormalities detected by ultrasound, especially urinogenital and
cardiovascular malformations.
27 of 65 (41.5%) fetuses that have been diagnosed with a VOUS, likely
pathogenic or likely benign in the report, decided to terminate the
pregnancy owing to the abnormal finding on ultrasound examination.
Others were live birth, except one was lost to follow up and the other
two were IUD.
In 66 fetuses with aneuploidy identified by CMA, 31/35 pregnancies with
trisomy 21 (include the two pregnancies whose ES results showed normal
and likely benign), 9/9 pregnancies with trisomy
18, 6/6 pregnancies with trisomy 13
and 13/16 other aneuploidy were terminated after receiving the genetic
reports. Two fetuses with trisomy 21 had IUD and one had PTB took place
before receiving the genetic result. The other 4 among the 66 women
finally decided to give birth to the babies.
60 out of 67 pregnancies with pathogenic CNV identified by CMA were
finally terminated. A woman with a CNV was IUD and another three was PTB
before receiving the genetic result. The other 3 women chose to continue
the pregnancy and gave birth to the fetuses finally.