When it comes to the best age to have a child, there is a nine-year Goldilocks zone for women.
That’s the conclusion of a study of more than 31,000 births, which found that women ages 23 to 32 had the lowest risk of birth defects.
Giving birth in the teens or early twenties increased the likelihood of the child being born with central nervous system defects that stunted brain and spinal development, while adult pregnancies were most closely associated with malformations from birth of the head, neck, the eyes and ears.
The researchers said their findings indicated a need for modernized pregnancy safety screening tools as the childbearing age in the developed world continues to age by the decade.
The lowest risk period of 10 years was between 23 and 32 years, and lower and higher ages at birth were almost equally risky
Men now have their first child on average at 26.4 years old, while women give birth for the first time at 23.7 years. Both have increased dramatically over the past two decades
The report also offers possible explanations for the different risks by age group, stating that young mothers are often unprepared for pregnancy and suffer from more unhealthy lifestyle factors such as drug and alcohol use.
Older women are longer exposed to environmental stressors such as air pollution, which the scientists say may contribute to their risk of several birth defects.
The study comes as the average age of new mothers in America hits an all-time high.
American women now give birth for the first time on average at the age of 30 27.2 years in 2000 and 24.6 years in 1970.
The rising age of first-time mothers has been attributed to numerous factors, including social and cultural shifts translating into delayed marriage and more time spent on leisure and travel, better prospects for women in the labor market, and financial constraints.
Scientists from the University of Semmelweis in Hungary analyzed data from 31,128 pregnancies with confirmed non-chromosomal birth defects registered in the Hungarian Case-Control Surveillance of Congenital Abnormalities between 1980 and 2009.
They compared that data to more than 2.8 million births registered with Hungary’s Central Bureau of Statistics during that same 30-year period.
Overall, the risk of nonchromosomal birth defects increased by about a fifth for births to women under 22 years of age. That risk increased by about 15 percent in women over age 32.
The most common and life-threatening complications affect the fetal circulatory system and, in the case of mothers under the age of 20, the central nervous system.
Younger mothers were 25 percent more likely to see defects in their babies’ central nervous system compared to older mothers.
Women who gave birth under the age of 20 saw an even greater risk of central nervous system malformations due to a problem with the development of the brain and/or spinal cord in the developing fetus, leading to serious conditions such as spina bifida .
Older mothers, on the other hand, showed a 100 percent higher risk of having a baby with deformities of the eyes, ears, face and neck caused by a baby’s skull or facial bones fusing together too early or in an abnormal way.
This can cause a baby’s ears to sit abnormally low on the head, the eyes to be medically small, or paralysis of the vocal cords.
Women on the older end of the spectrum were also more likely to have heart defects and more malformations of the urinary system.
And older mothers have a significantly higher chance — 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 risk of fetal genital malformations.
Dr. Boglárka Pethő, assistant professor at Semmelweis University and the study’s first author, said: ‘We can only assume why non-chromosomal birth defects are more likely to develop in certain age groups.
‘For young mothers, it can mainly be lifestyle factors (eg smoking, drug or alcohol use) and that they are often not prepared for a pregnancy.
‘In mothers at an advanced age, the accumulation of environmental effects, such as exposure to chemicals and air pollution, the deterioration of DNA repair mechanisms and aging of the egg cells and endometrium may also play a role.’
Previous research has confirmed that maternal age also increases the risk of having a baby with Down syndrome, an example of a genetic disorder. But less research has been done on non-genetic abnormalities
The number of American women with at least one child has fallen to just 52.1 percent, while the number of men has fallen to 39.7 percent in 2019
The report has been published in the journal BJOG: an international journal of obstetrics and gynaecology.
During a baby boom in the mid-20th century, the average woman gave birth to between three and four children. Just 1.6 children today – the lowest level recorded since records were first kept in 1800.
Women who become pregnant and give birth after age 35 tend to have more dangerous pregnancies. Older mothers may be at increased risk of miscarriage, high blood pressure, gestational diabetes and difficult childbirth.
The findings related to non-genetic birth defects that are not influenced by the mother’s genes.
Previous research has confirmed the link between older maternal age and certain genetic conditions, namely Down syndrome, for which the risk increases from about 1 in 1,250 for a woman who becomes pregnant at age 25 to about 1 in 100 for a woman who becomes pregnant at age 40.
prof. Nándor Ács, director of the Department of Obstetrics and Gynecology at Semmelweis University said: ‘Non-genetic birth defects can often develop due to the mother’s long-term exposure to environmental effects.
“As the childbearing age has been extremely reduced in the developed world, it is more important than ever to respond appropriately to this trend.”