The end point of any ovulation induction protocol is to
indentify the best time for triggering ovulation.
Most crucial step
Critical timing for HCG administation depends on the
criteria for follicular maturity
1. Follicular diameter
2. Serum E2
3. Endometrial thickness
Always time HCG with follicle size
Gnt follicles mature at 15-18 mm
CC follicles mature at 18-20 mm
HCG ovulation triggers
substitute for LH surge seen in spontaneous
Control the timing of ovulation
Timing of SI.
Timing of IUI
Timing of OR
HCG has a half-life of about 35 h: support the
initial part of the luteal phase.
similar activity to LH and binds to its receptor.
capable of inducing luteinization and ovulation.
Ovulation: 38 to 40 h after HCG injection.
2 types: urinary and recombinant
Urinary HCG dose: 5000-10,000 IU, IM.
Dose: 250 mcg, SC.
similar pharmacokinetics as the u HCG: ovulation
is expected following a similar time interval.
Preparation Trade name Route U.pr Price Company
IM 95% Organon
H.P.HCG Choriomon SC,
SC - Serono
SC - Serono
Types of HCG
I. Timing SI
Viable spermatozoa should be present in the female
genital system at the time of ovulation.
Sperms retain their fertilizing capacity for 40-80 h,
oocyte have life span of 12-24 h after ovulation.
between 2 days before & the day of ovulation:
Highest conception rate
On the day after ovulation: conception is zero.
≥24 h after ovulation then oocyte has already
Spontaneous ovulation can be expected when
the lead follicles 18-20 mm.
HCG trigger: when 1-2 follicle(s) is at a mature
It is very important to avoid stimulation of too many
mature (or close to mature) follicles because of the
ovulation can be induced with HCG) or (GnRHa).
Cochrane Database of Systematic Reviews
Evidence is inadequate to recommend or refute
the use of u hCG as an ovulation trigger in
anovulatory women treated with CC
No trials evaluating the use of ovulation triggers
in anovulatory women treated with other
II. Timing IUI
IUI should be performed around the moment of
ovulation. Since spermatozoa and oocytes have only
limited survival times correct timing is essential.
Methods for timing of ovulation:
1. Urinary LH surge: In natural cycles:
Follicular rupture occurs 36 h after the onset of serum LH rise.
A positive urine result is often found only 12 h after the onset of
LH surge in the serum (around the point of serum LH peak).
Serum LH surge >25mIU/ml
ovulation must be expected to occur on average as early as
24 h, after a positive urine test. If one adds a fertilizing life
span for the ovulated ovum of only 12 h to be on the safe
side, IUI 36 h after positive urine test is very satisfactory.Aboubakr Elnashar
Serum LH surge: 12 h
Urine LH surge (serum LH peak): 24 h
lunch-time (11.0-15.00) is the best time to check for
the LH surge using urine dipsticks and insemination at
any time between 18 and 53 h after the onset of the
surge will produce optimal results
(Khattab et al, 2005).
A spontaneous LH surge was noted in a variety of
follicular sizes (14 to 35 mm)
(Vlahos et al, 2005)
2. U/S and HCG triggering
The exogenous HCG mimics the endogenous LH surge
& offers the advantages that the onset of LH surge is
• HCG is given when the leading follicle is 17-20 mm.
• HCG should be withheld if
> 3 follicles > 16 mm:
(Macklon et al, 1999).
>4 follicles ≥ 14 mm
(Kamrava et al., 1982; Hugues et al., 2006).
b. Endometrial thickness:
<6 mm: No pregnancies
9-10 mm or more: The chance of pregnancy is great
(Isaacs et al, 1996).
3. E2 peak (pg/ml):
pregnancies are rare
risk of OHSS is significant
hCG is not given
Cyle is cancelled
(Speroff et al, 2006).
Chochrane. 2010 Cantineau et al
No significant differences between different
timing methods for IUI expressed as live birth rates:
hCG Vs LH surge
uhCG Vs rec hCG
hCG Vs GnRHa
The choice should be based on
convenience for the patient
Since different time intervals between hCG and IUI did
not result in different pregnancy rates, a more flexible
approach might be allowed.
24 0r 36 H after HCG
IUI 36 h after hCG has marginally better pregnancy
rates than 24 h.
Timing of insemination may be kept at 24 or 36 h
after hCG injection to suit the convenience of the
clinic or care provider.
(Rahman et al, 2011)
HCG 34-36 h before or after IUI
HCG after IUI: more closely resembles the
fertilization process in natural cycles.
PR were 10 and 12 % (P = 0.85), respectively.
HCG administration after IUI brought about no
improvement in PR.
HCG can be administered either before or after IUI.
(Firouzabai et al, 2013, Aydin et al, 2013)
III. Before OR
Ovulation occurs 35-42 h after the onset of LH surge
which trigers resumption of meiosis inside the oocyte:
OR is scheduled for at least 35 h after HCG
HCG: 3 or more follicles of size ≥17 mm
Timing of hCG in IVF/ICSI protocols using
GnRH agonist or antagonists: a systematic
review and meta-analysis
Chen et al, 2014
1295 participants were included.
Early Vs 24 –h late HCG
The prolongation of follicular phase by delaying
hCG administration could increase E2, P levels and
oocyte retrieval, which will not influence PR per
oocyte pick-up, miscarriage rate and live birth rate.
Postponing hCG may enable increased flexibility
of cycle scheduling to avoid weekend procedures.