Variations in Vascular Endothelial Growth Factor (VEGF) levels were prospectively evaluated in 18 young women undergoing in vitro fertilization treatments according to the “Long Protocol” and a typical pattern of VEGF levels was recorded. A significant increase in VEGF concentrations was observed only when the follicles reached a mean diameter of 15.3 mm in concurrence with mature oocyte retrieval. Since an increase in VEGF levels is related to follicular vascularity and oocyte developpment, our study supports the approach that oocyte retrieval may be performed when follicles > 15 mm in diameter appear. Anticipating egg retrieval in young patients with an optimal ovarian reserve may decrease the incidence of severe ovarian hyperstimulation, without compromising the treatment results.
The incidence of severe Ovarian Hyperstimulation Syndrome (OHSS) in gonadotropin-treated cycles is 0.5% - 3.0% [
VEGF, also known as Vascular Permeability Factor, is a homodimeric glycoprotein acting as an endothelial cell mitogenic/angiogenic factor [
In situ hybridization technique has been able to reveal the presence of VEGF mRNA in rat corpora lutea and cumulus oophorus of preovulatory follicles [
Serum VEGF concentrations are positively correlated with follicular fluid VEGF levels [
This prospective study was approved by the Institutional Review Board at the Soroka University Medical Center, Beer-Sheva, Israel, and included 18 young patients undergoing IVF due to male infertility (9 cases), pelvic adhesions (2 cases), and unexplained infertility (7 couples). The mean age of the 18 women in the study was 26.9 ± 1.7 years and the mean basic hormonal profile on the third day of the menstrual cycle was: estradiol 26.2 ± 26 pg/ml; FSH 5.5 ± 1.7 mIU/ml; LH 4.8 ± 2.6 mIU/ml.
The standard treatment regimen followed the “Long Protocol”, and ovarian down regulation was achieved by administration of controlled-release Gonadotropin Releasing Hormone (GnRH) agonist 3.75 mg (Decapeptyl C.R. 3.75 mg, Ferring Farmaceutical GmbH, Kiel, Germany) at the midluteal phase of the preceding cycle. Serum estradiol (E2) levels below 50 pg/mL 12 - 14 days following GnRH agonist injection were used to define ovarian quiescence. Controlled ovarian hyperstimulation was performed using hMG (Pergonal, Teva, Ramat-Gan, Israel) according to an individually adjusted technique monitored by serum estradiol (E2) and transvaginal ovarian sonography. Ten thousand Units of hCG (Chorigon, Teva, Ramat-Gan, Israel) were injected intramuscularly when serum E2 levels were at least 500 pg/ml and at least two follicles > 15 mm in diameter were observed. Mean gonadotrophin stimulation period per treatment cycle was 13 ± 0.9 days.
Transvaginal sonographically guided ovum retrieval was performed under general anesthesia 36 - 38 hours following hCG administration. The oocytes were inseminated or subjected to intracytoplasmic sperm injection (ICSI) according to the semen quality on the day of egg retrieval. Embryo transfer (ET) was performed 2 or 3 days later using embryos with the highest number of blastomers and having the highest embryo grading score.
Luteal phase was supported by five injections of hCG 1250 U every other day starting 48 hours after oocyte retrieval, or daily intramuscular administration of 50 mg progesterone (Gestone, Paines & Byrne Limited, West Byfleet, Surrey, UK) in patients at high risk for developing Ovarian Hyperstimulation Syndrome (peak E2 levels > 2000 pg/mL), or combined luteal support, adding four injections of hCG 1250 U every other day in progesterone-supported cycles in which the serum E2 and progesterone levels dropped sharply seven days following ET.
In all patients, serum b-hCG was obtained 14 - 17 days following ET and pregnancies confirmed by the presence of a pregnancy sac and cardiac activity on sonography.
Serum samples were obtained during IVF/ET treatment at the following time points: sample 1—ovarian down-regulation (12 - 14 days following GnRH agonist injection); samples 2, 3, and 4—during gonadotropin administration (follicular phase); sample 5—the day of egg retrieval; sample 6—day of ET; and samples 7, 8—seven and fourteen days following ET, respectively. The assessment of VEGF serum concentration was obtained using the Elisa Kit (VEGF Quantikine Human Immunoassay, R&D Systems Inc., Minneapolis, MN, USA).
Statistical analysis was performed two-tailed with Chisquare or Fisher exact test. Statistical significance was assumed at a p value < 0.05.
As shown in
Therefore, the follicular phase of the cycle was characterized by a gradual but statistically significant (p < 0.0006) reduction of the VEGF level between sample 1 (14 days following GnRHa injection) and sample 3 (9 - 11 days of ovarian stimulation). Thereafter, a significant increase (p < 0.002) in VEGF level between sample 3 and sample 4 (11 - 13 days of stimulation—hCG injection day) in concert with a continuous increase in E2 level and a rise in the mean follicular size from 14.1 mm to 15.3 mm were observed.
Samples 5-8 (
Embryo transfer was performed on day two or three using 3 ± 1 embryos per transfer. There was no difference in the number of retrieved oocytes or the fertilization rates between the study group and our general population. Three women achieved clinical pregnancy, but we could not observe a significant difference in VEGF serum levels in the pregnant women. None of the patients in the study group developed symptoms of severe OHSS.
Christenson and Stouffer [
Several studies have been able to demonstrate an association between increases in perifollicular blood flow on power Doppler ultrasound [
The timing of hCG administration that leads to the egg retrieval is typically guided by the follicle diameter and is based on the assumption that the follicular size predicts the ability of the eggs to be fertilized. The assumption is based on only a few clinical studies and recommends the leading follicle size of >18 mm as most suitable for egg retrieval [
Although the oocytes from smaller follicles give lower percentages of development [