1 Section of Child Life and Health, Department of Reproductive and Developmental Sciences, University of Edinburgh and 2 School of Computer Science, University of St Andrews, UK
3 To whom correspondence should be addressed at: Department of Haematology/Oncology, Royal Hospital for Sick Children, 17 Millerfield Place, Edinburgh EH9 1LW, UK. e-mail: Hamish.Wallace{at}luht.scot.nhs.uk
![]() |
Abstract |
---|
![]() ![]() ![]() ![]() ![]() ![]() |
---|
Key words: fertility counselling/human primordial follicle/ovarian reserve/ovarian volume/reproductive age
![]() |
Introduction |
---|
![]() ![]() ![]() ![]() ![]() ![]() |
---|
Several studies have reported the number of primordial ovarian follicles at different ages in humans. These data have been used to construct complex mathematical models of follicle decline (Block, 1952, 1953; Baker, 1963
; Gougeon, 1984
; Richardson et al., 1987
). During embryo development, several million germ cells are formed in the ovarian rudiment, several hundred thousand are present at birth and some 300 000 are present at menarche (Block, 1952
; Baker, 1963
). The precise number of primordial follicles remaining at menopause is unclear, but is of the order of 1000. Ovarian follicles were counted in the ovaries of 43 females aged 644 years, following accidental death, and, using linear extrapolation, the number of follicles present at menopause was predicted to be 2200 (Block, 1952
). This is now considered an overestimate, as further studies of follicle numbers present in the ovaries of pre- peri- and post-menopausal women have demonstrated that <1000 ovarian follicles remain in peri-menopausal women, indicating that follicle decline accelerates in the decade preceding menopause (Richardson et al., 1987
). With only an estimated 400 ovulations occurring during the reproductive period, this progressive reduction is attributed to follicle death by apoptosis. Follicle depletion as a result of atresia and recruitment towards ovulation leads to premature exhaustion of the follicle pool and menopause long before death (te Velde and Pearson, 2002
).
There currently are no reliable markers or clinical methods to assess ovarian reserve accurately in the normally menstruating pre-menopausal woman. Follicular density measured in ovarian biopsies from infertile women shows a significant negative correlation with increasing age. Women >35 years of age have a mean ovarian volume significantly smaller than in women <35 years, and have been shown to have only a third of the follicles of younger women (Lass et al., 1997a). An ovarian volume of <3 ml was predictive of a poor response to ovulation induction by HMG for IVF, very suggestive of reduced ovarian reserve (Lass et al., 1997b
). Furthermore, women with a low number of retrieved oocytes at ovulation induction for IVF were more likely to become post-menopausal at an earlier age than women with a higher number of retrieved oocytes (De Boer et al., 2002
)
Following the rapid increase in the use of transvaginal sonography, the measurement of ovarian volume has become quick, accurate and cost-effective. Ovarian volume measurement has become a potentially useful tool in the screening, diagnosis and monitoring of the treatment of conditions such as polycystic ovarian syndrome and ovarian cancer, and in the prediction of superovulation during IVF (Lass and Brinsden, 1999). The aim of this work is to describe a methodology for determining a womans reproductive age and ovarian reserve by measurement of ovarian volume by transvaginal sonography.
![]() |
Methods and Results |
---|
![]() ![]() ![]() ![]() ![]() ![]() |
---|
This equation expresses the rate of change in the population from birth, and we consider it to be the best model currently available. To find the population at a given age, y(x), we must solve the equation. This can be done either numerically or analytically. A numeric solution is inexact, but computation is designed to bound local errors, and, hopefully, minimize global errors. An analytical solution need not exist, and may be hard to find. It will, however, be exact (subject to careful evaluation of the terms involved). We solved the FaddyGosden equation using a 7th8th continuous RungeKutta numerical method (Butcher, 1987), and used the solution to estimate the radiosensitivity of the human oocyte (Wallace et al., 2003
). We have since solved the differential equation analytically using the Maple (Char, 1991
) computer algebra system; the two solutions agree to within 10 primordial follicles. Application of the FaddyGosden model for healthy women from birth to 51 years enables the average primordial follicle population to be determined for any given age (Figure 1).
|
|
Ovarian volume decreases with increasing age
Adult ovaries are ovoid, measure 35 cm (D1) x 1.53 cm (D2) x 0.61.5 cm (D3) and weigh 58 g (Clement, 1991
). During transvaginal sonography, the ovaries are measured in three planes and ovarian volume is calculated from the prolate ellipsoid formula V = D1 x D2 x D3 x 0.523. There is good evidence that adult ovarian volume decreases with increasing age as the remaining pool of primordial follicles becomes exhausted. As part of the University of Kentucky Ovarian Cancer Screening programme, 13 963 women between 25 and 91 years of age underwent annual transvaginal sonography. From 58 673 observations of ovarian volume, a statistically significant decrease in ovarian volume was shown with each decade of life from age 30 to 70 years (Figure 3). Mean (±SEM) ovarian volume was 6.6 (±0.19) ml in women <30 years old, 6.1 (±0.06) ml in women 3039 years, 4.8 (±0.03) ml in women aged 4049 years, 2.6 (±0.01) ml in women 5059 years old and 2.1 (±0.01) ml in women aged 6069 years. Mean ovarian volume was 4.9 ml in pre-menopausal women and 2.2 ml in post-menopausal women (Pavlik et al., 2000
).
|
|
|
In Figure 6, we describe the relationship between ovarian volume (as a surrogate measure for the remaining primordial follicle pool) and reproductive age for women of chronological ages 2545 years at 5 year intervals. The age at menopause for each age group is fixed at 50.4 years (Treloar, 1981), corresponding to an ovarian volume of 2.2 ml being the mean ovarian volume for post-menopausal women (Pavlik et al., 2000
). More specifically, if a woman of chronological age 2551 years has her mean ovarian volume measured by transvaginal sonography, then, taking ovarian volume data for her age from Pavlik et al. (2000
), we can estimate her reproductive age using ovarian volume as a surrogate for her ovarian reserve. We can then predict her age of menopause. This prediction will only apply to women who have no evidence of ovarian disease and who are not on hormonal contraception.
|
![]() |
Discussion |
---|
![]() ![]() ![]() ![]() ![]() ![]() |
---|
Evidence to support our first assumption that the observed variation in age at menopause is due to wide variation in the number of primordial follicles present at birth comes from the histological studies of the number of follicles in human ovaries at different ages. Reproductive ageing in women is due to exhaustion of the remaining pool of primordial follicles, with <1000 ovarian follicles remaining in peri-menopausal women (Richardson et al., 1987). It has been accepted for some time that it is a critical number of primordial follicles rather than a critical age that determines the timing of the menopause (Gosden, 1987
). The studies (Block, 1952
, 1953; Baker, 1963
; Gougeon, 1984
; Richardson et al., 1987
; Gougeon et al., 1994
) which counted primordial follicles in human ovaries provided the basis on which the FaddyGosden mathematical model was derived, but also clearly showed a wide variation in the number of primordial follicles present at birth and at all ages until the menopause. Furthermore, the age related-decline in the number of follicles is bi-exponential and more than doubles when numbers fall below a critical number of
25 000 (Faddy et al., 1992
). The wide variation in age at menopause of otherwise healthy Western women (Treloar, 1981
; Van Noord et al., 1997
) must be due to either variation in the rate of primordial follicle loss, for which there is no evidence, or a wide variation in the number of primordial follicles present at birth, for which there is good histological evidence (Baker, 1963
). The FaddyGosden solution for those women with an average age at menopause (Figure 1) can therefore be applied to those who are pre-programmed through a reduced (increased) number of primordial follicles at birth to have an early (late) menopause (Figure 2, lower panel).
Our second assumption is that ovarian volume between the ages of 25 and 50 years is directly related to the remaining primordial follicle population. The human ovary changes in size, shape and activity throughout life. At birth, the ovary is 1 cm in length and weighs <0.3 g (Clement, 1991
); there is continuous slow growth of the ovaries throughout childhood, and by puberty they have reached the size and shape of the adult ovary (Ivarsson et al., 1983
). The largest published study of ovarian volume related to age (Pavlik et al., 2000
) showed a statistically significant decrease in ovarian volume with each decade of life from 30 to 70 years. As we have shown, this steady decrease in ovarian volume throughout reproductive life significantly correlates with the number of primordial follicles present in the ovary as calculated from our solution of the FaddyGosden equation. Further evidence to support this relationship comes from studies of the ability of the ovary to respond to exogenous gonadotrophins for successful IVF. Women who have a mean ovarian volume of <3 ml have a very high chance of failure to respond to ovulation induction, implying significantly reduced ovarian reserve (Lass et al., 1997b
). In a further study of 60 infertile women aged 1945 years, which included an ovarian biopsy (Lass et al., 1997a
), a significant negative correlation between increasing age, ovarian volume and the density of primordial follicles in the ovarian cortex was found. A recent study (Erdem et al., 2003
) of both fertile (n = 53) and infertile (n = 62) women (aged 3545 years) showed a significant negative correlation between mean ovarian volume and age in both groups. Interestingly, basal FSH and antral follicle counts did not differ between infertile and fertile women, whereas mean ovarian volume was significantly smaller in the infertile women. These studies support a strong direct association between mean ovarian volume and remaining ovarian reserve. For ovarian volume to be used as a surrogate measure of the remaining primordial follicle pool, it is important for women to be assessed when they are not taking hormonal contraception because it appears that oral contraception reduces the volumes of both ovaries in all phases of the menstrual cycle (Christensen et al., 1997
).
The assessment of ovarian reserve in the otherwise healthy pre-menopausal woman remains a challenge. FSH in the early follicular phase of the menstrual cycle reflects the sum of both hypothalamic drive and ovarian feedback, but is not elevated until the peri-menopausal period (Wallach, 1995). Direct products of the ovary including inhibin B and anti-Mullerian hormone (AMH) have been investigated (De Vet et al., 2002
; Van Rooij et al., 2002
) as markers of a diminished ovarian reserve. The value of inhibin B is significantly increased following the administration of a single dose of FSH to stimulate granulosa cell function in small healthy follicles (Yong et al., 2003
). AMH, a member of the transforming growth factor-
family, is produced by granulosa cells of early developing follicles and is postulated to have a role in the regulation of human folliculogenesis (Durlinger et al., 1999
). Concentrations decrease over time in young normo-ovulatory women before other markers of ovarian ageing (De Vet et al., 2002
), and reduced baseline levels of AMH are associated with a poor response to ovarian stimulation for IVF (Van Rooij et al., 2002
). Interestingly, levels show little fluctuation over the menstrual cycle (Cook et al., 2000
). The measurement of AMH in the circulation is certainly a promising marker of ovarian ageing, but as yet it has not been shown to be helpful in assessing ovarian reserve for the individual.
The number of small antral follicles measuring between 2 and 10 mm in the early follicular phase of the menstrual cycle on transvaginal sonography was found to have the best correlation with chronological age in a study of 162 healthy female volunteers with proven normal fertility and regular menstrual cycles (Scheffer et al., 2003). The women were divided into three age groups; young (n = 49; 2534 years), middle (n = 53; 3540 years) and old (n = 60; 4146 years), and the number of small antral follicles fell significantly from median (range) 15 (330), 9 (125), 4 (117) in each group, respectively. Antral follicle counts have been used successfully to predict the ovarian response and pregnancy results of patients undergoing assisted reproductive technologies, with no pregnancies in the women with an antral follicle count of
3 (Chang et al., 1998
). Undoubtedly the number of small antral follicles reflects the remaining primordial follicle pool, but the wide range within each age group, and the large variation over concurrent cycles, makes interpretation difficult for the individual and it therefore remains at best an indirect test.
Fertility is a major concern for women who have survived cancer during childhood, and is of increasing importance because 70% of children treated for malignant disease will become long- term survivors (Mertens et al., 2001; Wallace et al., 2001
). Some women may develop an early menopause, but others may progress through puberty normally and have regular menstrual cycles with normal endocrine profiles (Wallace et al., 1989a
,b, 1993). As the agents used to treat childhood malignancy will destroy a greater or lesser number of ovarian primordial follicles, it would be of value to be able to assess accurately the effect of treatment on the ovarian reserve, particularly in those women with apparently normal ovarian function. Assessment of ovarian reserve in childhood cancer survivors with regular menstrual cycles and basal FSH <10 IU/l by repeated transvaginal sonography has shown that female survivors had significantly smaller ovarian volumes and a lower number of small antral follicles per ovary than controls (Larsen et al., 2003
). In a recent study, we have confirmed significantly reduced ovarian volumes and shown reduced serum AMH concentrations (Bath et al., 2003
), providing clear evidence for diminished ovarian reserve in regularly menstruating pre-menopausal childhood cancer survivors.
The ability to make a direct and accurate assessment of ovarian reserve would be of enormous benefit to women who are being considered for assisted reproductive technologies, for young women who are long-term survivors of childhood cancer and for women who are considering delaying starting a family for personal or professional reasons (Nikolaou and Templeton, 2003). Demographic (Wood, 1989
) and clinical (Noord-Zaadstra et al., 1991
) studies have shown that women experience their optimal fertility before the age of 3031 years, and it gradually declines towards the age of 40 years. The possibility of providing a direct and easily reproducible assessment of ovarian reserve and reproductive age through the transvaginal measurement of ovarian volume for all interested women is a real advance, and opens the door to the possibility of screening women for early ovarian ageing which currently affects 10% of the general population.
![]() |
Acknowledgements |
---|
![]() |
References |
---|
![]() ![]() ![]() ![]() ![]() ![]() |
---|
Bath LE, Wallace WHB, Shaw MP, Fitzpatrick C and Anderson RA (2003) Depletion of the ovarian reserve in young women following treatment for cancer in childhood: detection by anti-Mullerian hormone, inhibin B and ovarian ultrasound. Hum Reprod 18,23682374
Block E (1952) Quantitative morphological investigations of the follicular system in women: variations at different ages. Acta Anat 14,108123.
Block E (1953) A quantitative morphological investigations of the follicular system in newborn female infants. Acta Anat 17,201206.[Medline]
Butcher JC (1987) The Numerical Analysis of Ordinary Differential Equations: RungeKutta and General Linear Methods. Wiley, Chichester.
Chang M-Y, Chiang C-H, Hsieh T-T, Soong Y-K and Hsu K-H (1998) Use of the antral follicle count to predict the outcome of assisted reproductive technologies. Fertil Steril 69,505510.[CrossRef][Medline]
Char BW (1991) Maple V Reference Manual. Springer, Heidelberg.
Christensen JT, Boldsen J and Westergaard JG (1997) Ovarian volume in gynecologically healthy women using no contraception, or using IUD or oral contraception. Acta Obstet Gynecol 76,784789.
Clement PB (1991) Ovary. In Sternberg SS (ed.), Histology for Pathologists. Raven Press, New York, pp. 765795.
Cook CL, Siow Y, Taylor S and Fallat ME (2000) Serum mullerian inhibiting substance levels during normal menstrual cycles. Fertil Steril 73,859861.[CrossRef][Medline]
DeBoer EJ, den Tonkelaar I, te velde ER, Burger CW, Klip H and van Leeuwen FE (2002) A low number of retrieved oocytes at in-vitro fertilization treatment is predictive of early menopause. Fertil Steril 77,978985.[CrossRef][Medline]
DeVet A, Laven JSE, de Jong FH, Themmen APL and Fauser BCJM (2002) Antimullerian hormone serum levels: a putative marker of ovarian aging. Fertil Steril 77,357362.[CrossRef][Medline]
Durlinger AL, Kramer P, Karels B, de Jong FH, Uilenbroek JT, Grootegoed JA et al. (1999) Control of primordial follicle recruitment by anti-Mullerian hormone in the mouse ovary. Endocrinology 140,57895796.
Erdem M, Erdem A, Biberoglu K and Arslan M (2003) Age-related changes in ovarian volume, antral follicle counts and basal follicle stimulating hormone levels: comparison between fertile and infertile women. Gynecol Endocrinol 17,199205.[Medline]
Faddy MJ and Gosden RG (1996) A model conforming the decline in follicle numbers to the age of menopause in women. Hum Reprod 11,14841486.
Faddy MJ, Gosden RG, Gougeon A, Richardson SJ and Nelson JF (1992) Accelerated disappearance of ovarian follicles in mid-life: implications for forecasting menopause. Hum Reprod 7,13421346.[Abstract]
Gosden RG (1987) Follicular status at the menopause. Hum Reprod 2,617621.[Abstract]
Gougeon A (1984) Caractéres qualitatifs et quantitatifs de la population filliculaire dans lovaire humain adulte. Contracept Fertil Sexual 12,527.
Gougeon A, Ecochard R and Thalabard JC (1994) Age related changes of the population of human ovarian follicles: increase in the disappearance rate of non-growing and early-growing follicles in aging women. Biol Reprod 50,653663.[Abstract]
Ivarsson S-A, Nilsson KO and Persson P-H (1983) Ultrasonography of the pelvic organs in prepubertal and postpubertal girls. Arch Dis Child 58,352354.[Abstract]
Larsen EC, Muller J, Rechnitzer C, Schmieglow K and Andersen AN (2003) Diminished ovarian reserve in female childhood cancer survivors with regular menstrual cycles and basal FSH <10 IU/l. Hum Reprod 18,417422.
Lass A and Brinsden P (1999) The role of ovarian volume in reproductive medicine. Hum Reprod Update 5,256266.
Lass A, Silye R, Abrams D, Krausz T, Hovatta O, Margara R and Winston RML (1997a) Follicular density in ovarian biopsy of infertile women: a novel method to assess ovarian reserve. Hum Reprod 12,10281031.[CrossRef][Medline]
Lass A, Skull J, McVeigh E, Margara R and Winston RML (1997b) Measurement of ovarian volume by transvaginal sonography before ovulation induction with human menopausal gonadotrophin for in-vitro fertilization can predict poor response. Hum Reprod 12,294297.[Abstract]
Mertens AC, Yasui Y, Neglia JP, Potter JD, Nesbit ME Jr, Ruccione K, Smithson WA and Robison LL (2001) Late mortality experience in five-year survivors of childhood and adolescent cancer: the Childhood Cancer Survivor Study. J Clin Oncol. 19,31633172.
Nikolaou D and Templeton A (2003) Early ovarian ageing: a hypothesis. Hum Reprod 18,11371139.
Noord-Zaadstra BM, Looman CW, Alsbach H, Habbema JD, te Velde ER and Karbaat J (1991) Delaying childbearing: effect of age on fecundity and outcome of pregnancy. Br Med J 302,13611365.[Medline]
Pavlik E, DePriest PD, Gallion HH, Ueland FR, Reedy MB, Kryscio RJ and van Nagell JR (2000) Ovarian volume related to age. Gynecol Oncol 77,410412.[CrossRef][Medline]
Richardson SJ, Senikas V and Nelson JF (1987) Follicular depletion during the menopausal transition: evidence for accelerated loss and ultimate exhaustion. J Clin Endocrinol Metab 65,12311237.[Abstract]
Scheffer GJ, Broekmans FJM, Looman CWN, Blankenstein M, Fauser BCJM, de Jong FH and te Velde ER (2003) The number of antral follicles in normal women with proven fertility is the best reflection of reproductive age. Hum Reprod 18,700706.
teVelde ER and Pearson PL (2002) The variability of female reproduction ageing. Hum Reprod Update 8,141154.
Treloar A (1981) Menstrual cyclicity and the pre-menopause. Maturitas 3,249264.[Medline]
VanNoord PAH, Dubas JS, Dorland M, Boersma H and te Velde E (1997) Age at natural menopause in a population-based screening cohort: the role of menarche, fecundity, and lifestyle factors. Fertil Steril 68,95102.[CrossRef][Medline]
VanRooij IA, Broekmans FJ, te Velde ER, Fauser BC, Bancsi LF, Jong FH and Themmen AP (2002) Serum anti-Müllerian hormone levels: a novel measure of ovarian reserve. Hum Reprod 17,30653071
Wallace WHB, Shalet SM, Hendry JH, Morris-Jones PH and Gattamaneni HR (1989a) Ovarian failure following abdominal irradiation in childhood: the radiosensitivity of the human oocyte. Br J Radiol 62,995998.[Abstract]
Wallace WHB, Shalet SM, Crowne EC, Morris-Jones PH and Gattamaneni HR (1989b) Ovarian failure following abdominal irradiation in childhood: natural history and prognosis. Clin Oncol 1,7579.
Wallace WHB, Shalet SM, Tetlow LJ and Morris-Jones PH (1993) Ovarian function following the treatment of childhood acute lymphoblastic leukaemia. Med Pediatr Oncol 21,333339.[Medline]
Wallace WHB, Blacklay A, Eiser C, Davies H, Hawkins M, Levitt GA and Jenney MEM (2001) Developing strategies for long-term follow up of survivors of childhood cancer. Br Med J, 323,271274.
Wallace WHB, Thomson AB and Kelsey TW (2003) The radiosensitivity of the human oocyte. Hum Reprod 18,15.[CrossRef][Medline]
Wallach EE (1995) Pitfalls in evaluating the ovarian reserve. Fertil Steril 63,1214.[Medline]
Wood JW (1989) Fecundity and natural fertility in humans. Oxford Rev Reprod Biol 11,61109.[Medline]
Yong PYK, Baird DT, Thong KJ, McNeilly AS and Anderson RA (2003) Prospective analysis of the relationships between the ovarian follicle cohort and basal FSH concentration, the inhibin response to exogenous FSH and ovarian follicle number at different stages of the normal menstrual cycle and after pituitary down-regulation. Hum Reprod 18,3544.
Submitted on January 26, 2004; accepted on March 31, 2004.