Is there an incremental rise in the risk of obstetric intervention with increasing maternal age?

Objective To determine whether increasing maternal age increases the risk of operative delivery and to investigate whether such a trend is due to fetal or maternal factors.
Design Analysis of prospectively collected data on a maternity unit database.
Setting A postgraduate teaching hospital.
Population 6410 nulliparous women with singleton cephalic pregnancies delivering at term (37–42) weeks of gestation) between 1 January 92 and 31 December 95.
Main outcome measures Mode of delivery, rates of prelabour caesarean section, induction of labour and epidural usage.
Results There was a positive, highly significant association between increasing maternal age and obstetric intervention. Prelabour (  P < 0.001  ) and emergency (   P < 0.001  ) caesarean section, instrumental vaginal delivery (spontaneous labour   P < 0.001  ; induced labour   P = 0.001  ), induction of labour (   P < 0.001  ) and epidural usage in spontaneous labour (  P = 0.005  ) all increased with increasing age. In the second stage of labour fetal distress and failure to advance, requiring instrumental delivery, were both more likely with increasing maternal age (in both   P < 0.001  ). Epidural usage in induced labour and the incidence of small for gestational age newborns did not increase with increasing maternal age (P = 0.68 and  P = 0.50  , respectively).
Conclusions This study demonstrates that increasing maternal age is associated with an incremental increase in obstetric intervention. Previous studies have demonstrated a significant effect in women older than 35 years of age, but these data show changes on a continuum from teenage years. This finding may reflect a progressive, age-related deterioration in myometrial function.