Background
In New Zealand (NZ), Maori and Pacific women are less likely to complete prenatal screening for Down syndrome and other aneuploidies than other ethnic groups. Young women <20 have low rates of completed screening compared with women >20 years. Women living in deprived areas have lower completed screen rates than women living in more affluent areas. Combined first trimester screening has a superior sensitivity (85%) compared with second trimester screening (75%) for trisomy 21. The relative contribution of demographic factors to timing of screening uptake (first vs second trimester) has not previously been examined.

Aim
To evaluate the association of ethnicity, deprivation, District Health Board (DHB) of domicile and maternal age with timing of prenatal screening (first vs second trimester) in pregnant women screened in NZ from 2010 to 2013.

Methods and Materials
Univariate logistic regression analyses were used to explore the association between timing of completed screening and each of ethnicity, deprivation index, DHB of domicile and maternal age. Multivariate logistic regression models were developed to calculate odds ratios (OR) and 95% confidence intervals (CI). Statistical analyses were performed using SAS v9.3

Results
Of completed prenatal screens, 88% were completed in the first trimester. Ethnicity, age, deprivation and DHB were all significant predictors of completed first versus second trimester screening. Maori women were almost 60% less likely (adjusted OR 0.37, CI 0.35–0.39) and Pacific women almost 80% less likely (adjusted OR 0.23, CI 0.21–0.24) than NZ European women to have completed first versus second trimester screening. Women <30 years were less likely to have completed first trimester screening, as were more deprived women. Variation was also seen by DHB with women living in Whanganui DHB less likely to have completed first versus second trimester screening than women living in Auckland (adjusted OR 0.76, CI 0.71–0.81). Women living in Bay of Plenty DHB were more likely to be screened in the first versus second trimester compared with women living in Auckland (adjusted OR 1.55, CI 1.38–1.74). Within Auckland itself, women living in Counties Manukau DHB were less likely to be screened in the first versus second trimester than women living in Auckland DHB even after adjusting for ethnicity, deprivation and maternal age. Conclusion Maori and Pacific women have the lowest uptake of completed first versus second trimester screening after adjusting for age, deprivation and DHB. Research is required to understand if this relates to characteristics of the carer making the offer of screening, language and/or cultural barriers to care or specific collective cultural or religious views held by women from these ethnicities. The lower completed first trimester versus second trimester prenatal screening in deprived areas, as well as variation by DHB, may relate to the availability of ultrasound and/or laboratory services in specific regions. Cost may be a contributing factor to inequity in timing of completed prenatal screening uptake, as first trimester screening incurs a part‐charge to the individual, while second trimester screening is fully funded. Systemic factors within the NZ maternity model of care may also be contributory with a potential disconnect occurring for the woman between primary medical care and later registration with a Lead Maternity Carer in the first trimester.