Age-Related fertility decline: counselling & management.
Ageing can have a significant impact on both male and female fertility outcomes due to inherent natural biological processes. According to data released in October 2023 by the Australian Bureau of Statistics (ABS), the average age of both mothers and fathers has steadily increased since the mid-1970s. Sixty per cent of births are to mothers who are between 30-39 years, a sharp increase from less than 20% in 1975. The average number of children is also less.
Despite total fertility remaining low, the fertility rate for women in their late 30s and early 40s has significantly increased, with the fertility rate of mothers aged 35-39 years almost doubling from 36.0 to 69.3 births per 1,000 women, and for mothers aged 40-44 years, it has nearly tripled from 5.5 to 15.8 births per 1,000 women. This shift towards later parenthood for men and women follows trends to establish careers and securing economic independence before having children. This may appear to be reassuring for those who wish to delay parenthood, but it often results in increasing medical intervention to achieve one’s dreams of parenthood. This can be associated with increased financial pressures as well as physical and psychological morbidity, particularly when fertility treatment is not successful.
Whilst the spotlight has been focused primarily on maternal age, there is increasing evidence that suggests that the father's age contributes to his offspring's chance of having an inheritable disease. A literature review by Kaltsas et. al. shows a direct correlation between paternal age and decreased sperm quality and testicular function. Whilst the definition of advanced paternal age has been debated, it is thought that men over the age of 40 can have poorer reproductive outcomes. DNA mutations and chromosomal aneuploidies have all been linked to the father's advancing age. Increasing paternal age affects the success rate of in vitro fertilisation (IVF), intracytoplasmic sperm injection (ICSI), and increases premature birth rate. Several conditions, including autism, schizophrenia, bipolar disorders, and paediatric leukaemia, have been linked to the advanced paternal age.
There are several ways that age can affect fertility in women. Firstly, women are born with a set number of eggs that reduce over time. These eggs are exposed to radiation, unhealthy food choices, alcohol, smoking and endocrine disrupting agents which can all affect the quality which results in increasing genetic abnormalities.
This in turn can result in an increase in time to conception, a decreased chance of conception and increased miscarriage. The ability to fall pregnant declines more rapidly from the age of 37. Women who conceive later in life are more likely to conceive a pregnancy affected by autosomal aneuploidies such as trisomy 21, 13 and 18 and are advised to consider non-invasive prenatal testing after conception as well as additional first trimester screening tests.
Babies born to women aged ≥40 years have been shown to have a two-fold increased risk for cardiac defects, esophageal atresia, and craniosynostosis and therefore benefit from a detailed specialist ultrasound in pregnancy. Increasing maternal age is also associated with an increase in menstrual irregularity due to a decrease in cyclical production of estrogen and progesterone which impacts on the ability to conceive.
Key messages
Advanced maternal age leads to a decrease in fertility resulting in an increased need for ART
Early pregnancy complications are higher for women of advanced maternal age due to increased risk of chromosomal and genetic disorders
Women of advanced maternal age are at increased risk for late pregnancy complications, especially hypertension-related conditions, gestational diabetes, fetal growth restriction, preterm birth, and stillbirth.
Advancing age can also be associated with an increase chance of developing fibroids, polyps and adenomyosis all of which can impact on the ability to fall pregnant and can alter pregnancy outcomes.
Whilst the advent of Artificial Reproductive Technology (ART) has given the gift of a pregnancy to many couples, it should also be highlighted that advanced maternal age is associated with an increase in ectopic pregnancy, preterm delivery, gestational diabetes, hypertensive disorders in pregnancy, intrauterine growth restriction, placenta praevia, stillbirth, post-partum haemorrhage, caesarean section and peripartum hysterectomy.
A higher caesarean section rate has been largely attributed to labour dystocia with advanced maternal age regardless of parity and higher rates of postpartum depression that is delayed in onset is more common in women over the age of 35. Fertility treatment has enabled women with poor egg quality, diminished ovarian reserve or primary ovarian insufficiency to achieve a pregnancy with egg donation as can women who are perimenopausal.
The importance of preconception screening including metabolic screening cannot be underestimated, to identify women who are at increased risk in pregnancy to ensure that a pregnancy is safe for both the woman and the unborn child.
