Older moms more likely to have premature birth or complications

By Stephen Beech

Older mothers are more likely to give birth prematurely or suffer complications, warns new research.

Giving birth to a child after the age of 40 is becoming more common, but it can entail an increased risk to the child.

The new study, based on data from more than 300,000 births in Sweden, shows that babies of older moms are more often born prematurely or with complications, especially when the mother is 45 years of age or older.

In Sweden, just under one in 20 mothers (4.8%) were 40 years of age or older in 2022.

Previous studies have shown that older moms differ from younger mothers in several respects, including having a higher body mass index (BMI), a higher proportion having utilised reproductive technology, such as IVF, an increased risk of some diseases during pregnancy, and a higher proportion of Caesarean births.

The study, published in the journal Acta Pedriatica, looked at how the mother’s age affected the health of her newborn baby.

Researchers from Uppsala University and Linköping University analyzed data from Sweden’s National Medical Birth Register, which includes all pregnancies from week 22 that lead to childbirth.

A total of 312,221 children born to women over the age of 34 in the period 2010 to 2022 were included in the study, excluding twin births.

The babies were divided into three groups according to their mother’s age: 35 to 39, 40 to 44, plus 45 and older.

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The research team was particularly interested in how the health of the child at birth was affected when their mother was older than 39.

The children born to mothers aged 35 to 39 served as a reference group.

Study lead author Sofia Voss, of Uppsala University, said: “First of all, we could see that for babies born in Sweden, serious complications are rare, regardless of the mother’s age.

"But we also found that children of older mothers have a higher risk of stillbirth, premature birth, low birth weight relative to length of pregnancy, and low blood sugar compared to babies born to mothers aged 35 to 39.

"The study showed that the highest risks of all were to babies born to mothers 45 years and older.”

Stillbirth is uncommon in Sweden, but occurred in 0.83% of pregnancies in women who were 45 or older, compared to a rate of 0.42% in women aged 35 to 39.

Concerning premature birth, 4.8% of the cases occurred in the group of mothers aged 35 to 39.

Among women aged 40 to 44, the corresponding figure rose to 6.1%, and among women aged 45 or older, 8.4% of their babies were born prematurely.

Ms Voss added: “By comparing different ranges of advanced age when giving birth, the study can also contribute to better and better targeted information for women planning future pregnancies.

"As the share of older mothers rises, our study can help to target screening and interventions where they will have the most benefit.

"But it’s also important to inform the public so that they can make informed choices."