Objectives To describe the consequences in terms of health outcomes, care and associated healthcare costs for three hypothetical cohorts of women planning their first pregnancy at a fixed, different age.

Design Decision model based on data from perinatal registries and the literature.

Setting The Netherlands.

Population 3 hypothetical cohorts of 100 000 women aged 23, 29 and 36 years, planning a first pregnancy.

Main outcome measures Live birth, pregnancy complications for mother and child and associated healthcare costs.

Results For the three cohorts of 23-, 29- and 36-year-old women, 1.6%, 4.6% and 14% of women would not succeed in an ongoing pregnancy (spontaneous or after assisted reproductive technology). The cohort aged 36 gave 9% more miscarriages, 8% more fertility treatment and 1.4% more multiple births than the cohort aged 29. The proportion of caesarean sections among low risk women was 4.9% and 11% higher respectively for the cohorts aged 29 and 36, compared with the cohort aged 23 at start. Eventually, 98%, 95% and 85% of the women in each of the three cohorts gave live birth. The costs for the two older cohorts were €415 and €1662 higher per ongoing pregnancy than the cohort aged 23 years.

Conclusions Spontaneous conception and mode of delivery are most susceptible to increasing maternal age leading to involuntary childlessness and non-spontaneous labour. The increase in assisted reproduction technology, twin pregnancies and delivery complications results in higher costs along with fewer ongoing pregnancies at higher age.