Background
Timely engagement in antenatal care improves maternal and child health outcomes and is an important element of healthcare performance measurement.

Aims
To describe the timeliness of lead maternity carer (LMC) engagement and identify the factors associated with timely engagement.

Materials and Methods
The Growing Up in New Zealand longitudinal study enrolled a diverse sample of pregnant women during 2009 and 2010. Timely engagement was defined as before ten weeks gestation. Independent associations of LMC type; maternal ethnicity, age, parity and education, and household deprivation with timely engagement were described using odds ratios (OR) and 95% confidence intervals (CIs).

Results
Of the 6822 women enrolled, 6661 (98%) stated they had a LMC. Of these 6661, 6012 (90%) reported the time taken to engage a LMC. Eighty‐six to 92% of women engaged a LMC in a timely manner depending upon the estimate of gestational time used. Factors independently associated with delayed engagement were Māori (odds ratio (OR) = 0.59, 95% CI 0.44–0.80), Pacific (0.63, 0.46–0.86) or Asian (0.51, 0.39–0.67) ethnicity; first pregnancy (0.71, 0.58–0.88); age <20 years (0.62, 0.41–0.94); socio‐economic deprivation (0.69, 0.52–0.92); and LMC type being a hospital midwife (0.47, 0.38–0.60), or a combination of care providers (0.60, 0.42–0.90). Conclusions Timeliness of LMC engagement in NZ is poorer for non‐European women, younger women, women in their first pregnancy, and women living in more socioeconomically deprived areas. Improving the timeliness of LMC engagement for these groups of women has the potential to reduce inequalities in maternal and child health outcomes.