Contribution of maternal age, medical and obstetric history to maternal and perinatal morbidity/mortality for women...

As age is not modifiable, pregnancy risk information based on age alone is unhelpful for older women.

To determine severe morbidity/mortality rates for women aged ≥35 years according to maternal profile based on parity, pre-existing medical conditions and prior pregnancy complications, and to assess the independent contribution of age.

Population-based record-linkage study using NSW hospitalisation and birth records 2006-2012. Maternal and perinatal mortality/morbidity were assessed for non-anomalous singleton births to women aged ≥35 years.

For 117 357 pregnancies among 99 375 women aged ≥35 years, the median age at delivery was 37 years (range 35-56 years), including: 35 652 (30.4%) multiparae without pre-existing medical or obstetric complications, 33,058 (28.2%) nulliparae without pre-existing medical conditions and 30 325 (25.8%) multiparae with prior pregnancy complications. Maternal and perinatal mortality/morbidity varied by maternal profile with ranges of 0.9-3.5% and 2.4-11.9%, respectively. For nulliparae, each five-year increase in age did not contribute significantly to maternal risk after controlling for medical conditions (adjustedodds ratio 1.08, 95% CI 0.93-1.25), but did confer perinatal risk (1.14; 1.05-1.25). For multiparae, each five-year increase in age beyond 35 years was independently associated with adverse maternal (1.23; 1.09-1.39) and perinatal outcomes (1.23; 1.09-1.39).

For women aged ≥35 years, presence of medical conditions conferred a greater risk for morbidity/mortality than age itself. For multiparous women, the effects of medical and obstetric history were additive. The contribution of maternal age to adverse outcomes in pregnancies without significant medical and obstetric history is modest.