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Individualised risks of stillbirth at advanced maternal age: A literature review of the evidence


Introduction: Women worldwide are having their babies later than in previous generations. Advanced maternal age (AMA) has been associated with adverse pregnancy outcomes, the most severe being increased risk of stillbirth. This literature review examines the evidence for risk of stillbirth at term for women aged 40 or over in high income countries, and outlines factors found in the literature that amplify or mitigate the risk. The aim is to assist New Zealand (NZ) AMA women to make informed choices around induction of labour (IOL) which is frequently recommended at 39 weeks gestation as a general district health board (DHB) guideline for women of AMA.

Methods: Databases searched included Google Scholar, CINAHL, Science Direct, PubMed, ProQuest, and Cochrane. Seven papers met the inclusion criteria. Stillbirth risk was assessed against the exacerbating or mitigating factors within the individual papers and compared, if appropriate. Guideline documents regarding NZ obstetric recommendations for AMA were also hand searched.

Findings: The risk of stillbirth is associated with increasing maternal age beyond age 40 with the range of adjusted odds ratios (AORs) of 1.43 to 3.04. However, absolute risk of stillbirth for Australian and NZ women over age 40 remains very low at 4.05 stillbirths/1000 undelivered pregnancies, or an absolute risk factor above a baseline rate of 3.4/1000 for stillbirths (>24wks). Further, the stillbirth risk for women of AMA may be modified by parity and general health.

Conclusion: AMA is associated with increasing stillbirth rates, although the absolute rate remains low and can potentially be modified by parity and general health. Therefore, women of AMA in the NZ context have the opportunity to assess their overall risk in consultation with their maternity carer, including these factors, when making a decision about early term IOL.

Keywords: stillbirth, advanced maternal age, induction of labour, New Zealand

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