Giving birth aged 23 to 32 cuts risk of some congenital conditions

The optimum age for giving birth to reduce the baby’s risk of certain health conditions is between 23 and 32, according to a study in Hungary, although the chances remain low at all ages looked at.

The likelihood of having a baby with Down’s syndrome or other medical conditions caused by alterations to chromosomes – the packages of DNA – was already known to increase with age.

But it was unclear how age at the time of birth affects the baby’s risk of being born with another group of conditions, collectively known as non-chromosomal anomalies (NCAs). These encompass a diverse range of conditions, including cleft palate, club foot and disorders of the heart, genitals, brain, lungs and digestive system.

They are thought to have a range of causes, including maternal infection, poor diet and exposure to toxins, pollutants or radiation while the fetus is developing, although the specific trigger is usually unknown for any given case, says Boglárka Pethő at Semmelweis University in Budapest, Hungary.

To investigate the impact of age on NCAs, Pethő and her colleagues analysed a register of births and stillbirths involving congenital conditions that had been kept in Hungary between 1980 and 2009, as well as abortions that had been carried out because of such conditions. They excluded cases with chromosomal anomalies and milder NCAs, such as hernias.

The researchers also looked at the total number of live births – nearly 3 million over the period studied – and broke it down by the mother’s age at birth to calculate the risk of having a baby with an NCA at every age. Overall, about 1 in 100 of the babies would have had one of the conditions.

They found that the chance of an NCA was lowest in the women aged between 23 and 32. In those older than that, there was a 15 per cent higher chance of such a birth, while there was a 20 per cent higher chance in the younger women.

In women older than 32, the chance of NCAs may be higher because their eggs are older, says Pethő, although in women younger than 23, the higher risk may be because they are more likely to smoke, take drugs and drink, although the study didn’t investigate causes.

“This is an interesting study including a very large number of babies,” says Asma Khalil, vice-president for academia and strategy at the UK’s Royal College of Obstetricians and Gynaecologists. However, “the risks to the babies born to mothers outside of the [23 to 32] age range are still small”, she says. For instance, the chance of women younger than 23 having a baby with an NCA is about 1.2 in 100.