When it comes to the best age for having children, there is a nine-year Goldilocks zone for women.
That’s the conclusion of a study of more than 31,000 births, which showed that women aged 23 to 32 had the lowest risk of birth defects.
Teenage moms and women in their early twenties were more likely to give birth to children with defects to the central nervous system, affecting things like brain and spine development, while mature pregnancies were associated most closely with deformities of the head, neck, eyes, and ears.
Young mothers are often unprepared for pregnancy and must contend with more unhealthy lifestyle factors such as drug and alcohol use, the researchers said.
Older women have been exposed to environmental stressors such as air pollution for longer, which the team believes may contribute to their risk of different birth defects.
The window for having a baby safely is fairly narrow, according to researchers, and the risk factors for various birth defects vary based on maternal age
The lowest risk 10-year period was between 23 and 32 years, and lower and higher ages at birth were almost equally risky
Men are now having their first child at 26.4 years old on average, while women are giving birth for the first time at 23.7. Both have increased greatly in the last two decades
The study comes as the average age of new moms in America hits its highest point on record.
American women are now giving birth for the first time at age 30 on average, up from 27 in 2000 and 24 in 1970.
The rising age of new mothers has been attributed to changing family values, women prioritizing their careers, and the rising cost of living.
For the latest study, scientists at Semmelweis University in Hungary analyzed data from 31,128 pregnancies with confirmed non-chromosomal birth defects recorded in an official Hungarian database between 1980 and 2009.
They compared that data with more than 2.8 million births registered in the country during that same 30-year period.
Overall, the risk of birth defects increased by about a fifth for births in women under the age of 22 compared to those within the ideal childbearing window of ages 23 to 32.
That risk increased by about 15 percent in women above the age of 32 when compared to those within the optimal age window.
The most common and life-threatening complications affected the fetus’ circulatory system and, in the case of mothers under 20, the central nervous system.
Compared to older mothers, younger moms were 25 percent more likely to see defects in their babies’ brains and central nervous systems, leading to serious conditions such as spina bifida, compared to older mothers.
Women who gave birth younger than 20 saw an even greater risk of these problems relative to women 23 to 32.
Older mothers, on the other hand, were twice as likely to have a baby with malformations of the eyes, ears, face, and neck caused by an infant’s skull or facial bones fusing together too soon or in an abnormal way.
This can lead to a baby’s ears being situated abnormally low on the head, their eyes being medically too small, or vocal cord paralysis.
Women on the older end of the spectrum were also more likely to see heart defects as well as more malformations of the urinary system than those in the healthy age window.
And older mothers have a considerably higher likelihood – 45 percent in fact – of giving birth to a baby with a cleft lip and palate, while a younger mother’s risk increases by nine percent.
While the risk of birth defects in the digestive system was higher for younger mothers than older ones – 23 percent and 15 percent respectively – older mothers had a slightly higher chance of fetal genital malformations.
The findings pertained to non-chromosomal and non-genetic birth defects which are not influenced by the mother’s genes. Some non-genetic, non-chromosomal causes of birth defects include alcohol and tobacco use in pregnancy, the presence of certain medical conditions and being on certain medications while pregnant.
Dr Boglárka Pethő, assistant professor at Semmelweis University and the first author of the study said: ‘We can only assume why non-chromosomal birth anomalies are more likely to develop in certain age groups.
‘For young mothers, it could be mainly lifestyle factors (e.g., smoking, drug or alcohol consumption) and that they are often not prepared for pregnancy.
‘Among advanced-aged mothers, the accumulation of environmental effects such as exposure to chemicals and air pollution, the deterioration of DNA repair mechanisms, and the ageing of the eggs and endometrium can also play a role.’
Previous research has confirmed that increased maternal age likewise increases the risk of having a baby with Down’s Syndrome, an example of a genetic disorder. But less research has been conducted in the case of non-genetic anomalies
The number of American women with at least one child has fallen to just 52.1 percent, while the number of men dropped to 39.7 percent in 2019
The report was published in the journal BJOG: an International Journal of Obstetrics & Gynaecology.
A baby boom in the mid-20th century saw the average woman give birth to between three and four children. Today, just 1.6 children – the lowest level recorded since data was first tracked in 1800.
Women who get pregnant and give birth beyond age 35 typically have more dangerous pregnancies. Older mothers may be at increased risk of miscarriage, high blood pressure, gestational diabetes, and a difficult labor.
Previous research has confirmed the association between older maternal age and certain genetic disorders, namely Down’s syndrome, for which the risk increases from about 1 in 1,250 for a woman who conceives at age 25, to about 1 in 100 for a woman who conceives at age 40.
Prof. Nándor Ács, director of the Department of Obstetrics and Gynecology at Semmelweis University, said: ‘Non-genetic birth disorders can often develop from the mothers’ long-term exposure to environmental effects.
‘Since the childbearing age in the developed world has been pushed back to an extreme extent, it is more important than ever to react appropriately to this trend.’