Advanced maternal age
Advanced maternal age, in a broad sense, is the instance of a woman being of an older age at a stage of reproduction, although there are various definitions of specific age and stage of reproduction. The variability in definitions regarding age is in part explained by the effects of increasing age occurring as a continuum rather than as a threshold effect. The most commonly used definition of advanced maternal age is 35 years or more at the time of childbirth.
In Western, Northern, and Southern Europe, first-time mothers are on average 26 to 29 years old, up from 23 to 25 years at the start of the 1970s. In a number of European countries (Spain), the mean age of women at first childbirth has now even crossed the 30 year threshold.
This process is not restricted to Europe. Asia, Japan and the United States are all seeing average age at first birth on the rise, and increasingly the process is spreading to countries in the developing world like China, Turkey and Iran. In the U.S., the average age of first childbirth was 25.4 in 2010.
Having children later was not exceptional in the past, when families were larger and women often continued bearing children until the end of their reproductive age. What is so radical about this recent transformation is that it is the age at which women give birth to their first child which is becoming comparatively high, leaving an ever more constricted window of biological opportunity for second and subsequent children should they be desired. Unsurprisingly, high first-birth ages and rapid rates of birth postponement are associated with the arrival of low, and lowest-low fertility.
This association has now become especially clear since the postponement of first births in a number of countries has now continued unabated for more than three decades, and has become one of the most prominent characteristics of fertility patterns in developed societies. A variety of authors (in particular Lesthaeghe) have argued that fertility postponement constitutes the ‘hallmark’ of what has become known as the second demographic transition.
Others have proposed that the postponement process itself constitutes a separate 'third transition'. On this latter view modern developed societies exhibit a kind of dual fertility regime, with the majority of births being concentrated either among very young or increasingly older mothers. This is sometimes known as the 'rectangularisation' of fertility patterns.
Decreased fertility 
A woman's fertility peaks in the early and mid twenties, after which it starts to decline, with advanced maternal age causing an increased risk of female infertility.
According to Henri Leridon, PhD, an epidemiologist with the French Institute of Health and Medical Research, of women trying to get pregnant, without using fertility drugs or in vitro fertilization: 
- At age 30
- 75% will have a conception ending in a live birth within one year
- 91% will have a conception ending in a live birth within four years.
- At age 35
- 66% will have a conception ending in a live birth within one year
- 84% will have a conception ending in a live birth within four years.
- At age 40
- 44% will have a conception ending in a live birth within one year
- 64% will have a conception ending in a live birth within four years.
Risk of birth defects 
A woman's risk of having a baby with chromosomal abnormalities increases with her age. Down syndrome is the most common chromosomal birth defect, and a woman's risk of having a baby with Down syndrome is:
- At age 25, 1 in 1,250
- At age 30, 1 in 1,000
- At age 35, 1 in 400
- At age 40, 1 in 100
- At age 45, 1 in 30
- At age 49, 1 in 10
Other effects 
The risk of the mother dying before the child becomes an adult increases by more advanced maternal age, such as can be demonstrated by the following data from France in 2007:
|Maternal age at childbirth||25||30||35||40||45|
|Risk of mother not surviving until child's 18th birthday (in %)||1.0||1.6||2.6||3.8||5.5|
On the other hand, advanced maternal age is associated with a more stable family environment, higher socio-economic position, higher income and better living conditions, as well as better parenting practices, but it is more or less uncertain whether these entities are effects of advanced maternal age, are contributors to advanced maternal age, or common effects of a certain state such as personality type.
Explanations for birth postponement 
A variety of explanations have been offered as to why people postpone parenthood.
Increase in education levels 
A delay is normally associated with increasing levels of education. Post-industrial economies exhibit an ever-increasing demand for highly educated and flexible workers. For the individual, the pursuit of higher education constitutes the principal pathway for finding a stable job, securing a higher salary, and for increasing career prospects generally. As a result most young people remain enrolled in some form of education well into early adulthood.
The anticipated number of years post-compulsory education is now as high as 8.5 years in France, and up to half of all those in the 20-24 age group (and even between 50% and 55% in Denmark, Finland, and France) are enrolled in full-time or part-time studies. Women have especially benefited from this development and now form more than half of the graduate and postgraduate students in a majority of European countries. Such education expansion evidently has a direct implication for fertility trends.
Employment and motherhood 
Women face a potential conflict between employment and motherhood. This conflict, which is fuelled by rapidly increasing education level and labor force participation among women, constitutes one of the most widely debated issues in contemporary fertility research.
Traditionally, employment and motherhood were seen as incompatible roles, and Gary Becker’s argument that the increasing gender equality which gives rise to greater earning power for women increases both their labor force participation and the opportunity costs of childbearing, consequently reducing the demand for children. Recent studies, however, have increasingly found that the relationship between labor force participation and fertility is not a straightforward one and may be filtered through a number of additional factors. Looked at dynamically it is not hard to argue that compatibility between family life and labor force participation, as impacted by societal differences, cohort membership, age, and education all serve to modify this relationship.
In the past, many women became employed but with the mindset that when they married or became pregnant they would withdraw from the workforce. More recently women have begun to enter the workforce with a long-term mindset where they invest more and, instead of working intermittent jobs, plan a career. These women tend to marry later and give birth at more advanced ages to first put together a career. The ability for mothers to persist in employment after the birth of a child remains subject to intense pressure.
As much as labor force participation per se, security of employment is thought to be important, and the widespread presence of part-time and temporary employment at the younger ages are thought to persuade many to delay pregnancy. This is not an unequivocal view, since the availability of part-time employment may be thought to act in a pro-natal direction, making motherhood and employment continuity possible, and it may be rather the employment stability of the father which is the key factor.
- economic uncertainty, related to the “economic precariousness of an individual’s employment and educational enrollment circumstances,”
- temporal uncertainty, and
- employment relationship uncertainty, reflecting the type and precariousness of the employment contract.
In the Mills-Blossfeld framework, being unemployed leads to a high level of an individual’s economic uncertainty, whereas rising unemployment rates could lead to higher temporal uncertainty. Young adults are increasingly susceptible to all forms of uncertainty, especially with regard to their employment, which has a disproportionate impact on disadvantaged—especially less educated—social groups.
In addition, the rapid pace of change, the unpredictability of social and economic developments, and the overflow of information create uncertainty about possible behavioural outcomes as well as about the probability of these outcomes, and about the amount of information to be collected for a particular decision. Unsurprisingly these authors suggest that the rapid rise of globalisation has been a key factor associated with increasing the levels of each of the these three types of uncertainty.
Changes in interpregnancy interval 
Kalberer et al. have shown that despite the older maternal age at birth of the first child, the time span between the birth of the first and the second child (= interpregnancy interval) decreased over the last decades. If purely biological factors were at work here, it could be argued that interpregnancy interval should have increased, as fertility declines with age, which would make it harder for the woman to get a second child after postponed birth of the first one. This not being the case shows that sociologic factors (see above) prime over biological factors in determining interpregnancy interval.
With technology developments cases of post-menopausal pregnancies have occurred, and there are several known cases of older women carrying a pregnancy to term, usually with in vitro fertilization of a donor egg. A 61-year-old Brazilian woman with implantation of a donor egg expected her first child September 2011.
See also 
- Effect of advanced age on fertility and pregnancy in women at UpToDate. Author: Ruth C Fretts. Section Editor: Louise Wilkins-Haug. Deputy Editor: Vanessa A Barss. This topic last updated: Dec 3, 2012.
- Huang, L.; Sauve, R.; Birkett, N.; Fergusson, D.; Van Walraven, C. (2008). "Maternal age and risk of stillbirth: A systematic review". Canadian Medical Association Journal 178 (2): 165–172. doi:10.1503/cmaj.070150. PMC 2175002. PMID 18195290.
- Kohler, H. P.; Billari, F. C. and Ortega, J. A. (2002). "The emergence of lowest-low fertility in Europe during the 1990s". Population and Development Review 28 (4): 641–680.
-   Leridon, H. (2004). "Can assisted reproduction technology compensate for the natural decline in fertility with age? A model assessment". Human Reproduction 19 (7): 1548–1553. doi:10.1093/humrep/deh304. PMID 15205397.
- "American Society for Reproductive Medicine (ASRM). Age and Fertility: A Guide for Patients ASRM, Birmingham, AL, 2003". March of Dimes. Archived from the original on 30 January 2009. Retrieved 2/5/09.
- Nelson, S. M.; Telfer, E. E.; Anderson, R. A. (2012). "The ageing ovary and uterus: New biological insights". Human Reproduction Update 19 (1): 67–83. doi:10.1093/humupd/dms043. PMC 3508627. PMID 23103636.
- Schmidt, L.; Sobotka, T.; Bentzen, J. G.; Nyboe Andersen, A.; on behalf of the ESHRE Reproduction Society Task Force (2011). "Demographic and medical consequences of the postponement of parenthood". Human Reproduction Update 18 (1): 29–43. doi:10.1093/humupd/dmr040. PMID 21989171.
- Kalberer U, Baud D, Fontanet A, Hohlfeld P, de Ziegler D. Birth records from Swiss married couples analyzed over the past 35 years reveal an aging of first-time mothers by 5.1 years while the interpregnancy interval has shortened. Fertil Steril. 2009 Dec;92(6):2072-3.
- "Woman, 61, pregnant". The Sydney Morning Herald. 27 September 2011.
Further reading 
- Hofmeister, Heather; Mills, Melinda; Blossfeld, Hans-Peter (2003), Globalization, Uncertainty and Women’s Mid-Career Life Courses: A Theoretical Framework. University of Bamberg, Working Papers PDF
- Lesthaeghe, R. and Neels, K. (2002). "From the first to the second demographic transition: An interpretation of the spatial continuity of demographic innovation in France, Belgium and Switzerland". European Journal of Population 18 (4): 325–360.
- Sobotka, Tomás (2004). "Postponement of childbearing and low fertility in Europe, Dissertation". University of Groningen.
- Gavrilov, L.A., Gavrilova, N.S. Human longevity and parental age at conception. In: J.-M.Robine, T.B.L. Kirkwood, M. Allard (eds.) Sex and Longevity: Sexuality, Gender, Reproduction, Parenthood, Berlin, Heidelberg: Springer-Verlag, 2000, 7-31.
- Gavrilov, L.A., Gavrilova, N.S. Parental age at conception and offspring longevity. Reviews in Clinical Gerontology, 1997, 7: 5-12.
- The Fertility Bust, Charlemagne, The Economist, February 9 2006
- Low and Lowest-Low Fertility in Europe: Causes, Implications and Policy Options. By H-P Kohler, F.C. Billari and J.A Ortega. University of Pennsylvania, 2005.
- Postponement of childbearing and low fertility in Europe Power Point presentation by Tomas Sobotka
- InterNational Council on Infertility Information Dissemination