No. of Small Antral Follicles Can Predict IVF Pregnancy


HAMBURG, GERMANY — The presence of small antral follicles measuring 2.1–4.0 mm predicted pregnancy and ovarian response in a prospective cohort of 142 women who underwent in vitro fertilization.

The study took advantage of a novel software program called sonography-based automated volume count (SonoAVC) that can automatically identify and measure the dimensions of hypoechogenic areas such as ovarian follicles observed on 3-D ultrasonography. In this instance, the program was used to calculate the number of antral follicles measuring 9 mm or less in diameter in the early follicular phase (days 2–5) in subfertile women (aged 40 years or less) who were due to undergo their first cycle of assisted reproductive technology.

In all, 73 viable pregnancies were confirmed on ultrasound 7 weeks following embryo transfer.

Women who conceived had significantly more antral follicles measuring 2.1–4.0 mm than did those who had unsuccessful treatment, Nick Raine-Fenning, Ph.D., and his colleagues reported at the World Congress on Ultrasound in Obstetrics and Gynecology. There were no significant differences among women with antral follicles measuring 4.1–6.0 mm, 6.1–8.0 mm, or 8.1–9.0 mm.

On multiple logistic regression analysis, the number of antral follicles measuring 2.1–4.0 mm was a significant independent predictor of pregnancy (odds ratio, 1.23), said Dr. Raine-Fenning of the University of Nottingham (England). The total number of antral follicles and younger age also were significant predictors, while other antral follicle subgroups and type of treatment were not.

“These early results are encouraging, as very few studies have shown a link [between the number of these small follicles and] eventual pregnancy outcome,” they said.

Larger follicles are more likely to be atretic and of poorer quality, while smaller antral follicles relate more closely to serum levels of anti-Müllerian hormone and may better reflect the quality of the oocyte, Dr. Raine-Fenning said in an interview.

Current tests of ovarian reserve are considered quantitative, in that they give an idea of how many oocytes one can expect during in vitro fertilization (IVF) treatment, but are not qualitative, as they cannot predict pregnancy, he noted.

Among women who conceived in the current study versus those who did not, there were more mature oocytes (10.73 vs. 9.04), fertilized oocytes (7.26 vs. 5.81), and cleaved embryos (6.89 vs. 5.53). The number of small antral follicles 2.1–4.0 mm in size was a significant predictor for all three of these secondary outcomes both in univariate and multivariate analyses, Dr. Raine-Fenning reported.

Earlier this year, the investigators reported that SonoAVC identified a comparable number of follicles to real-time 2-D ultrasound in a preliminary study of 72 women undergoing their first cycle of assisted reproductive technology. Follicle tracking with SonoAVC did not significantly improve the number of mature oocytes retrieved, however, when compared with conventional ultrasound (11.43 vs. 10.70) or clinical pregnancy rates (43% vs. 42%).

The SonoAVC software is available only with a few General Electric ultrasound machines, but the additional cost of the software should be reclaimed in improved efficiency in the IVF unit, Dr. Raine-Fenning said.

He reported no relevant financial conflicts of interest.

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