Nitric oxide donors and
implantation
ROWAA A. MOSTAFA
MD, FRCOG
Implantation is a progressive process in
which the embryo has to appose and
attach
itself
to
the
maternal
endometrium, and invade it. This process
involves 2 sides:
Endometrium
Embryo
Since the introduction of IVF ,there has
been substantial improvement of all IVF
steps. However, the endpoint, which is to
improve implantation and pregnancy
rates after transferring adequate number
of embryos remains below expectations.
The main reason for this disappointing
result is the quality of the endometrial
factor that is affected during COH . The
fundamental question is : could
implantation be improved in ART,
therefore increasing the pregnancy rates in
IVF/ ICSI cycles?
Adjuvant medical therapies to
improve implantation
Several medical therapies were tried as adjuvants
with progesterone to increase endometrial
receptivity and improve implantation after ET.
 Aspirin.
 Ascorbic acid .
 Vitamin E.
 Corticosteroids.
 Heparin.


Luteal E2 supplementation.
Nitric oxide donors.
Nitric oxide donors
NO donors are compounds capable of releasing free
NO in vivo.
Several observations were behind the trials of using
nitric oxide donors in ART in attempt to improve
endometrial receptivity and implantation.
These observations include




No acts as a relaxant of blood vessels and smooth muscles of uterus.
No inhibits platelets aggregation.
NOS reaches peak levels in the endometrium during implantation
window in natural cycle.
Adequate uterine perfusion is an important factor in uterine receptivity.
Various studies showed that high resistance to uterine blood flow at
HCG time or at ET is correlated with poor outcome. Using Doppler
ultrasonography, Goswamy and Steptoe, 1988 reported a high
incidence of poor uterine perfusion in women with repeated failed
IVF trials. They postulated that sub-optimal uterine blood flow
could possibly be an independent factor of infertility.
Types of NO donors:
Organic:
* Isosorbide mononitrate (ISMN).
* Isosorbide dinitrate (ISDN).
* Isosorbide trinitrate (ISTN).
* Nitroglycerine.
 Non organic:
* Nicorandial.
* Molsidomine.

A study was carried to assess the effect of
nitric oxide donor on uterine blood flow
,
endometrial
receptivity
and
implantation in IVF/ICSI . A better
understanding of implantation is essential
for further improvement of success rates
in assisted conception treatment cycles
Subjects and Methods
The present study was conducted in Fertility
IVF center in the period from September 2006
to May 2008. Forty women whom ICSI was
indicated
for
male
factor
(
oligoasthenosprmia) were selected for this study.
Their ages ranged from 25 to 35 year. . There
were no other indications for ICSI in all
participating women. Cases of PCOD were not
included.
The subjects received the long protocol of
controlled ovarian hyper-stimulation
using GnRH analogue decapeptyl 0.1 mg;
Ferring and HMG , 75 IU FSH and LH;
Menogon ,Ferring 2-3 amp /day.
HCG ,pregnyl; Organon 10 000 IU was given by
IMI when ≥ 3 follicles with a mean diameter of
18 mm or more were seen. Oocytes retrieval
was done 36 hours later followed by ICSI. Each
woman had ET of 2 or 3 good quality embryos
on day 3 after oocytes retrieval. Cases with only
one embryo available for transfer and /or no
grade A embryos, were not included.
Luteal phase support was undertaken
with progesterone vaginal pessaries (
Cyclogest 400mg daily) starting on the
day of oocytes retrieval and for 2 weeks
after embryo transfer. Measurement of
B-HCG was done after 2 weeks and if it is
positive, transvaginal ultrasound scan is
done 2 weeks later to assess the
pregnancy.
The subjects were divided randomly into 2
groups after embryo transfer.
Group I: 20 women received nitric oxide
donors in the form of nitroglycerin skin
patch(Nitroderm 5mg/24 hours) Novartis
pharma S.A.E; Basles Switzerland. The patch
releases transdermal propanetriol trinitrate.
The patches were used for 2 weeks.
Group II: the other 20 women did not receive
this treatment.
Nitroderm TTs is a flat
multilayer system designed
to deliver nitroglycerin
continuously through a
release a release membrane
following application to the
skin. The active substance
penetrates the skin and thus
becomes directly bioavailable
to the systemic circulation .
Three Nitroderm skin patches are available:
TTS 5, TTS 10 and TTS 15. The figures
denote the nominal amount of nitroglycerin
in mg delivered by the system in 24 hours.
The rate of release is 20-25 ug/cm2. hr.
TTS 5 was used in the current study.
Uterine artery doppler blood flow assessment
was done for all women on the day of HCG
administration and one week later. The
pulsatility index (PI) was used for this purpose.
PI
= peak systolic- end diastolic
mean velocity for the entire cardiac cycle
Transvainal probe 5 MHz of Color
doppler ultrasonography (Digital GAIA ,
Sonace 8800, Medison; S.Korea )
machine was used. All scans were done
by experienced operators and almost in
the same time of the day to avoid diurnal
variation in the uterine blood flow.
Transvaginal pelvic scanning was first
performed and the morphology of the
uterus and ovaries was explored. Color
flow mapping and pulsed Doppler
measurements were performed to the
uterine artery on both sides. Blood flow
velocity waveforms were obtained and
quantitated by the calculation of
pulsatility index (PI).
Results
Table(1) patients characteristics
Group I
Group I I
p
Age(mean±SD)ys
29.8 ±3.0
30.6 ±2.7
BMI(mean±SD)
27.7 ± 3.4
26.4 ±3.5
>0.05
N.S
Years of infertility
((mean ±SD)
7.4 ± 2.9
6.1 ± 3.8
>0.05
N.S
>0.05
Signif.
N.S
Table (2) characteristics of treatment cycles
Group I Group II
(mean)
(mean)
P
HMG ampoules
34.5±3.2 37.8 ±4.1 >0.05
HMG days
11.4±2.3 12.5±3.8
>0.05
Retrieved oocytes
7.4 ±2.2 8.7±3.1
>0.05
Fertilized oocytes
5.9±1.3 6.1±1.0
> 0.05
Fertilization rate
79.7±5.3% 73.1±4.8% >0.05
Transferred embryos 2.1± 0.5
2.5 ± 0.2 >0.05
Signif.
N.S
N.S
N.S
N.S
N.S
N.S
Table (3) outcome of the trial
Group I
Mean PI on day HCG
Mean PI after 1 wk
No of pregnancies
singleton
twin
Pregnancy rate
Implantation rate
2.76 ±0.77
2.01 ± 0.52
8
6
2
40%
21.7 %
Group II
2.83±0.56
2.70±0.42
6
6
0
30%
13.1%
P
>0.05
<0.05
>0.05
<0.05
Signif.
NS
S
NS
S
Table (4) PI and pregnancy
No of cases
No of pregnancies
PI on HCG day
low(1-1.99)
medium (2-2.99)
high (>3.0)
4
29
7
3
11
0
PI after 1 week
low
medium
high
7
30
3
5
9
0
Conclusions



Implantation process constitutes the limiting
factor to increase pregnancy rates in ART.
Optimal uterine perfusion is an important
factor for uterine receptivity and consequently
successful implantation.
Nitric oxide donors may hove a role in
optimizing uterine blood flow and perfusion.
Their use may improve implantation which can
increase pregnancy rate in ART treatment
cycles.