Enter both parents’ ages to explore age-related estimates for Down syndrome, autism and other pregnancy and child health outcomes.
Your age-related results*
Autism: study comparisons
These are relative comparisons with parents aged 20–29, not your child’s percentage chance of autism.
Other commonly discussed outcomes
- Patau syndrome (trisomy 13): also associated with maternal age. No individual percentage is calculated here.
- ADHD and learning or developmental differences: these two ages are not enough to calculate a reliable personal probability.
- Structural birth defects, including heart defects: age alone cannot predict whether a baby will have one. Prenatal ultrasound checks anatomy separately from chromosome screening.
- Gestational diabetes and pre-eclampsia:
- Preterm birth, low birth weight and stillbirth: older maternal age is associated with higher rates in population studies. Health, pregnancy history and the course of the pregnancy also matter; an age-only percentage would be incomplete.
Other notable associations
Advancing paternal age has also been linked with some rare genetic conditions, including achondroplasia and Apert syndrome, and with schizophrenia and some childhood cancers. The evidence and size of the association vary. These outcomes remain uncommon, and this calculator does not estimate a personal chance for them.
*These are separate population estimates and associations, not a diagnosis or an overall chance of having a healthy baby. Family history, health, screening and diagnostic results can change an individual assessment.
Methodology
Chromosome conditions: the Down syndrome and Edwards syndrome numbers use Prenatal Screening Ontario’s published table for each whole maternal age from 21 to 45 at the expected birth. Each is a chance at birth, before incorporating your own screening or diagnostic results. The percentage is 100 divided by the table’s “1 in” denominator. Outside this range, the calculator shows no number rather than extending the table. Male age does not alter these estimates.
Autism: the comparisons come from Sandin and colleagues’ five-country cohort of about 5.8 million children born in 1985–2004. Each relative risk adjusts for the other parent’s age, birth year, child’s sex and study site. Results include the 95% confidence interval; an interval spanning 1.00 does not show a clear difference from the reference group. The reported age bands are used without interpolation. The oldest maternal band covers ages 40–55 and the oldest paternal band 50–71. Outside the observed age ranges, no number is shown. These historical relative risks are not current prevalence estimates, and an association does not establish a cause.
Miscarriage: age-group percentages come from Magnus and colleagues’ Norwegian register study of 421,201 pregnancies in 2009–2013, using the estimates adjusted for induced abortions. They describe loss across a recognized pregnancy, not the remaining chance after a particular week or scan. The age bands are under 20, 20–24, 25–29, 30–34, 35–39, 40–44 and 45 or older. Here the numerical reference is limited to ages 15–49, rather than extrapolating to unusually young or old ages. A birthday during pregnancy may place you in an adjacent group. Paternal-age findings come from a separate systematic review and are not multiplied into this percentage.
Scope: these estimates concern different outcomes, populations and time periods. They cannot be added or subtracted from 100% to make an overall score. The calculator does not use fertility, family history, donor ages, egg- or sperm-freezing age, health conditions or prenatal test results. It does not estimate the chance of conception.
Common questions
Can these ages tell me whether my baby will have autism or Down syndrome?
No. Age is one piece of population-level information. Chromosome screening can refine an estimate, and diagnostic testing can confirm certain chromosome conditions. Autism is assessed through development and behaviour; an age calculation cannot diagnose it.
Why does changing male age leave some numbers unchanged?
The chromosome and miscarriage tables shown here are based on maternal age. Male age changes the autism study comparison and the paternal-age context. There is no validated combined formula in this calculator for those other outcomes.
Is there an age when these risks suddenly become high?
Age-related changes generally occur gradually. Study age bands and clinical age thresholds are useful groupings, not biological switches on a birthday.
Sources
- Prenatal Screening Ontario: chance of chromosome differences based on age — trisomy 21 and 18 at birth.
- Sandin et al., Molecular Psychiatry (2016) — parental age and autism, Table 2 and its age-range footnote.
- Magnus et al., BMJ (2019) — maternal age and miscarriage, Table 1.
- du Fossé et al., Human Reproduction Update (2020) — paternal age and miscarriage systematic review.
- ACOG/SMFM: pregnancy at age 35 years or older — pregnancy complications and fetal assessment.
- ASRM (2025): advancing paternal and maternal age — other paternal-age associations.
- CDC: about ADHD; CDC: diagnosing autism.
- ACOG: screening for fetal chromosomal abnormalities — screening and diagnostic assessment.