Advanced maternal age
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 such as China, Turkey and Iran.
[4] Advanced maternal age is associated with adverse reproductive effects including increased risk of infertility,[5] and chromosomal abnormalities in children.
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.
[9] 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.
[10] On this latter view, modern developed societies exhibit a kind of dual fertility pattern, with the majority of births being concentrated either among very young or increasingly older mothers.
[4] The German Federal Institute for Population Research stated in 2015 the percentage for women with an age of at least 35 giving birth to a child was 25.9%.
[14] A woman's fertility peaks lasts during the twenties and first half of thirties, after which it starts to decline, with advanced maternal age causing an increased risk of female infertility.
A qualitative study on couples in the United States who used in-vitro fertilization to conceive their first child when the woman was aged 40 or older at the time of delivery found that 72% of the women and 57% of the men believed that they had enhanced emotional preparedness for parenting which benefitted both their children and themselves.
[22] In quantitative studies, mother's older age at first birth has been associated with increases in children's psychiatric health,[23] language skills,[23] cognitive ability,[24] and fewer social and emotional difficulties.
If purely biological factors were at work, 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.
As ovarian reserve and fertility decline with age, there is also a parallel increase in pregnancy failure and meiotic errors resulting in chromosomally abnormal conceptions.
