Risks Of Delaying Pregnancy Until Age 35 Years Or Older
Everyone is aware of the ticking of the biological clock, but does your 35th birthday represent a particularly special milestone in biology? Do you hit 35 and suddenly become "high risk" overnight?
Women are delivering healthy babies throughout their 30s and beyond. The age of 35 is simply an age that certain risks become more worthy of discussion.
While these risks become slightly more likely after hitting 35 years old, this does not mean that they will have a significant impact on everyone in their mid-thirties and older.
Decline in fertility
Women are born with all the eggs they will ever have. As females age, the likelihood that they will get pregnant reduces due to the declining number of remaining eggs and their reduced quality.
Fertility also declines in men with age due to declining sperm counts, motility, and semen volume. These age-related factors combined can make it more difficult for women to become pregnant.
One study, published in The New England Journal of Medicine, found that among women who received artificial insemination, 74 percent of those under 31 years old were pregnant within a year. However, this decreased to 61 percent of individuals between the ages of 31 to 34, and it further declined to 54 percent of women aged 35 and over.
Certain genetic risks present more often in pregnancy as women age. For example, the rate of having a baby with Down syndrome accelerates with maternal age.
While the rate of an embryo having Down syndrome at the 10-week mark of pregnancy is 1 in 1,064 at age 25, this rises to 1 in 686 at age 30 and 1 in 240 by the age of 35 years. At the age of 40, the Down syndrome rate increases still to 1 in 53, and down to 1 in 19 embryos at age 45.
A study published in Nature Communications set out to investigate why older mothers have a heightened risk of giving birth to children with congenital anomalies that are characterized by abnormal chromosome numbers.
Researchers from the Albert Einstein College of Medicine of Yeshiva University in New York learned that the genetic process of recombination could be responsible for the increased risk of conditions such as Down syndrome.
Recombination is the process in which pairs of chromosomes exchange genetic material before separating. The team found that in older mothers, the process of recombination may be less regulated, which may lead to abnormal chromosome numbers in sex cells or large chromosomal rearrangements.
The risk of miscarriage climbs gradually with the mother's age. Research published in the BMJ showed that risk of miscarriage is around 8.9 percent for women aged 20 to 24 years and increases to 74.7 percent for individuals aged 45 years or above. The declining quality of women's eggs is thought to be responsible for the higher rates of miscarriage.
Stillbirth is more likely in older women than younger women. Asystematic review published in the Canadian Medical Association Journal found that stillbirth is around 1.2 to 2.23 times higher in older women.
Another study, examining data from 385,120 pregnancies in the United Kingdom, observed that the rate of stillbirth was 4.7 per 1,000 for women aged 18 to 34, 6.1 per 1,000 between the ages of 35 and 40 years, and 8.1 per 1,000 for women aged 40 and over.
Furthermore, the stillbirth rate has been shown to be higher in people having their first child and even higher in first-time moms aged 35 or older.
Women aged 35 years and older are often recommended to be induced as they approach their due date because of the increasing risk of stillbirth with gestational age. Around 1 in 1,000 women under 35 years old have a stillbirth during 39 and 40 weeks of gestation, compared with 1.4 in 1,000 women aged 35 to 39, and 2 in 1,000 women at age 40 and above.
The reasons that stillbirth rates increase with maternal age are currently unclear.
Research comparing pregnancy complications among women aged 18 to 34 years, 35 to 40 years, and 40 and over, found small increases in most pregnancy- and birth-related complications with age.
Birthing outcomes such as emergency cesarean delivery and postpartum hemorrhage are increased with maternal age.
The researchers identified increases in the risk of gestational diabetes, placenta previa, breech positioning of the baby, emergency cesarean delivery, postpartum hemorrhage, preterm birth, low birth weight, and high birth weight. Other research has found that risk of maternal mortality also increases with age.
Research presented at the American Stroke Association's International Stroke Conference 2016 revealed that compared with women who go through pregnancy at a younger age, pregnant women aged 40 and older are at greater risk of ischemic stroke, hemorrhagic stroke, heart attack, and death from cardiovascular disease.
"We already knew that older women were more likely than younger women to experience health problems during their pregnancy," said Dr. Adnan I. Qureshi, director of the Zeenat Qureshi Stroke Institute in St. Cloud, MN. "Now, we know that the consequences of that later pregnancy stretch years into the future."
Dr. Qureshi and colleagues found that all the risks, except for hemorrhagic stroke, were explained by well-known risk factors for cardiovascular disease - such as high blood pressure, diabetes, and high cholesterol - that older pregnant women face.