12. Oocyte Retrieval in IVM
KeywordsIVMPick upNeedleOocyte management for in vitro maturation
Transvaginal oocyte retrieval during assisted reproductive technologies (ARTs) was first introduced in 1981, replacing both surgical egg collection and laparoscopic retrieval but also previous different approaches such as the transurethral ultrasound-guided route. It is well known that the number of oocytes retrieved depends on many factors: type of aspiration needle (wide or narrow bore or single or double channel), aspiration pressure, follicular flushing, timing of HCG triggering, and experience and skills of the surgeon.
Follicle diameter and fluid volume
Follicle diameter (mm)
Fluid volume (mL)
Hemisphere surface area (mm2)
Thus antral follicles of 3 mm may contain a competent oocyte, but will have approximately 1/300th the amount of fluid of a normal dominant follicle, with practical consequences on the oocyte aspiration technique .
Bevel of the needle
Rigidity of the needle
Critical aspects to deal with are also the higher risk of bleeding and pain for the patient during and after the collection of immature eggs.
Seyhan et al. analyzed pain scores with different gauge needles comparing a 19-gauge needle for IVM with a 16- or 17-gauge IVF needle: they found a trend of lower pain scores with 19-gauge needle, although not statistically significant; they suggested that smaller needles could give a more comfortable collection, even if in IVF enlarged ovaries with multiple large follicles and higher aspiration pressure could cause more pain. It is likely that within the range of conventional needles, smaller size results in less pain intra- and postoperatively, with a similar number of collected oocytes .
This may be particularly important in ART settings in which limited anesthesia is available for the patient. Seyhan et al. compared IVM patients in cases using a 19-gauge needle to IVF patients in cases using a 16- or 17-gauge needle. Records on 375 patients were reviewed retrospectively.
There were several approaches to anesthesia, but 233 patients received conscious sedation with midazolam and fentanyl together with a paracervical block.
Patients ranked the amount of pain they experienced during the procedure on a scale of 1 to 10. There was no difference in the pain experience of the groups. Note that in addition to different gauge needles, this study compared different aspiration procedures since IVF required passage of the needle through the vagina and into each ovary only once, whereas IVM required a number of punctures in each ovary.
The authors viewed the results as showing that a smaller gauge needle was less traumatic since multiple insertions of the 19-gauge needle caused no more pain than two insertions of the larger needle. Several studies from the IVF literature also suggest that smaller needles cause less pain for women who are lightly sedated during retrieval; however, more studies are needed to confirm this.
Manufacturer (identification number)
Needle length (cm)
Bevel length (mm)
Bevel angle (degrees)a
Needle dead space (mL)a
Total dead space (mL)
Length ultrasound scoring (mm)
Ultrasound scoring begins
Flow rate (mL/s)b
Cooper-Smith, Trumbull, CT(AR-N1695)
Cook Medical, Spencer, IN (K-OPSD-1635-A-S-US)
1 mm above bevel top
Smiths. Medical, Kent, UK (Wallace, 0NS1733LL-500)
Smiths Medical, Kent, UK (Wallace, ONS18333LL-500)
Cook Medical, Spencer, IN (K-OPS-7035-RWH-ET)
2 mm above bevel top
IVFETFLEX.com, Ganz, Austria (Steiner-Tan 21 gauge)
0.5 mm above bevel top