Table 1

Maternal characteristics by midwifery years of experience (births 2008–2014)

	1st year		2nd–5th years		6th–10th years		11th–20th years		After 20th year		Unknown		P values*
	n=19 948		n=60 894		n=66 474		n=96 855		n=75 314		n=25 425
	n	%	n	%	n	%	n	%	n	%	n	%
Ethnicity†
Māori	6151	30.84	17 737	29.13	18 352	27.61	26 310	27.16	16 306	21.65	6265	24.64
Pacific	2120	10.63	4758	7.81	5633	8.47	10 234	10.57	5663	7.52	2163	8.51
Indian	682	3.42	1595	2.62	1756	2.64	3129	3.23	2438	3.24	773	3.04
Other Asian	1918	9.61	5309	8.72	5970	8.98	7370	7.61	5302	7.04	1581	6.22
MELAA	388	1.95	1083	1.78	1055	1.59	1691	1.75	1491	1.98	460	1.81
European	8689	43.56	30 406	49.93	33 702	50.70	48 114	49.68	44 105	58.56	14 181	55.78	<0.001
Unknown	0	0.00	6	0.01	6	0.01	7	0.01	9	0.01	2	0.01
Age†
<20	2171	10.88	5132	8.43	4533	6.82	5815	6.00	3641	4.83	1557	6.12
20–24	4877	24.45	13 741	22.57	13 349	20.08	17 366	17.93	11 007	14.61	4624	18.19
25–34	9991	50.09	32 339	53.11	36 343	54.67	53 774	55.52	41 924	55.67	13 855	54.49
35–39	2426	12.16	8000	13.14	10 173	15.30	16 367	16.90	15 441	20.50	4504	17.71
≥40	483	2.42	1682	2.76	2076	3.12	3533	3.65	3301	4.38	885	3.48	<0.001
Deprivation quintile†
1	2333	11.70	7754	12.73	9016	13.56	13 291	13.72	12 094	16.06	3332	13.11
2	2606	13.06	9585	15.74	10 072	15.15	14 003	14.46	12 505	16.60	4532	17.82
3	3654	18.32	11 929	19.59	12 951	19.48	17 385	17.95	15 444	20.51	5390	21.20
4	5325	26.69	15 714	25.81	16 281	24.49	23 628	24.40	17 908	23.78	5561	21.87
5	5931	29.73	15 609	25.63	17 849	26.85	28 073	28.98	17 003	22.58	6514	25.62	<0.001
Unknown	99	0.50	303	0.50	305	0.46	475	0.49	360	0.48	96	0.38
Parity†
0	10 311	51.69	26 952	44.26	25 833	38.86	36 488	37.67	28 277	37.55	10 155	39.94
1–2	7571	37.95	27 751	45.57	33 077	49.76	48 103	49.66	38 681	51.36	12 510	49.20
3	1045	5.24	3331	5.47	4148	6.24	6481	6.69	4675	6.21	1569	6.17
≥4	1017	5.10	2855	4.69	3414	5.14	5775	5.96	3676	4.88	1187	4.67	<0.001
Unknown	4	0.02	5	0.01	2	0.00	8	0.01	5	0.01	4	0.02
Smoking at booking†
Yes	4419	22.15	11 829	19.43	11 423	17.18	15 164	15.66	9719	12.90	3902	15.35
No	15 523	77.82	49 052	80.55	55 043	82.80	81 676	84.33	65 587	87.08	21 513	84.61	<0.001
Missing	6	0.03	13	0.02	8	0.01	15	0.02	8	0.01	10	0.04
BMI†
<18.5	640	3.21	1862	3.06	1945	2.93	2507	2.59	1954	2.59	653	2.57
18.5–24.99	9648	48.37	29 987	49.24	33 136	49.85	46 767	48.29	39 042	51.84	12 798	50.34
25–29.99	5072	25.43	15 776	25.91	17 336	26.08	25 247	26.07	19 461	25.84	6525	25.66
30–34.99	2701	13.54	8009	13.15	8301	12.49	13 109	13.53	9008	11.96	3170	12.47
35–39.99	1182	5.93	3308	5.43	3623	5.45	5798	5.99	3638	4.83	1432	5.63
≥40	660	3.31	1828	3.00	1979	2.98	3185	3.29	2038	2.71	784	3.08	<0.001
Missing or <15 or >100	45	0.23	124	0.20	154	0.23	242	0.25	173	0.23	63	0.25

*Excludes unknown; χ² test.
↵†Data from MAT.
BMI, body mass index; MAT, National Maternity Collection; MELAA, Middle-Eastern, Latin American or African.