Follicle Tracking for IVF
Follicle tracking involves tracking the development of eggs
within the ovary from an immature state (primordial follicles)
to a mature state (leading or dominant follicles). This process
may be monitored with transvaginal ultrasound in combination
with blood levels of the female hormones oestrogen and progesterone.
Follicles may be tracked in a natural cycle. When a leading
follicle is seen (average size=22mm , with a range of 17-27mm)
then intercourse may be appropriately timed. Alternatively
drugs which promote release of the mature egg (leutinising
hormone)may be administered.
For most patients on IVF treatment however, the ovaries
are artificially stimulated with hormones (follicle stimulating
hormone) which produces multiple mature eggs which are then
harvested following administration of luteinising hormone.
In this setting the follicular development is followed more
closely. Usually between 2-4 scans and blood sampling are
performed per treatment cycle. The timing of ultrasound guided
needle aspiration of mature follicles is based on the scan
and blood results.
If the eggs are less mature than expected the timing of
egg collection is postponed and where the follicular development
is in advance of the expected time then the date of egg collection
is brought forward.
In most patients egg collection is performed as a transvaginal
ultrasound guided procedure under anaesthetic. However in
some patients in view of difficulty with vaginal access it
may be performed transabdominally.
In some patients pain may be experienced following the procedure
and if this pain worsens then an ultrasound examination may
be performed to determine the presence or absence of internal
haemorrhage after collection.
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