A retrospective population based cohort study from the United States has found a modest correlation between older paternal age and adverse perinatal outcomes.

A total of 40,529,905 documented live births occurring between 2007 and 2016 in the United States were evaluated. Paternal and maternal demographic data, and maternal and child perinatal and pregnancy outcome data, were extracted from national databases.

Paternal age was categorised as: < 25, 25-34, 35-44, 45-54 and ≥ 55 years. For statistical analysis the reference paternal age group was 25-34 years. Over the ten-year study period, the mean paternal age increased from 30.0 to 31.2 years.

After adjustment for maternal age, race, education, smoking status, and number of prenatal vists, births related to older fathers were associated with poorer outcomes.

For children born to fathers aged 45-54 years compared with those born to fathers aged 25-34 years:

• Gestational ages were lower by 0.12 weeks (99% CI: -0.13 to -0.11)

• The odds of a pre-term birth (< 37 weeks) were 14% higher; adjusted odds ratio (OR) 1.14 (99% CI: 1.13-1.15)

• Birthweight was 20.2 g lighter (99% CI: -22.5 to -18.0)

• The odds for low birthweight (< 2,500 g) were 14% higher OR 1.14 (99% CI: 1.12-1.15).

The odds of a low 5-minute Apgar score (<8) were OR 1.14 (99% CI: 1.08-1.20) for children of fathers aged 55 years or over compared with the reference age group.

Although the odds ratios were significant they were all less than 1.5.

The only adverse neonatal events that had a statistically significant poorer score were assisted ventilation and admission to neonatal ICU. Again, the odds ratios, although statistically significant, were only marginally worse among the children of older fathers.

The global adjusted adverse event risks to children of fathers aged 45-54 and ≥ 55 years were 1.12 (99% CI: 1.11-1.13) and 1.24 (99% CI: 1.20-1.28) respectively.

Observational studies, such as this one can only demonstrate association never causation.

The study authors conclude:

‘While it is important to note that the absolute risk of advancing paternal age on adverse perinatal conditions remains modest, our findings emphasise the need to further investigate the public health implications of increasing paternal age within the US and other countries.’

‘Preconception counselling guidelines might need to change to incorporate the possibility that delaying parenthood for fathers might not be as inconsequential as previously understood,’ they say.

Dr Chris Barclay