Table 2.

Partner change between pregnancies by second pregnancy complications and maternal characteristics

		Partner
		Same	Different
	Number	Rate (%)	Rate (%)
Second pregnancy complications
Term (>37 weeks) pre-eclampsia	5196	1.17	1.37
Preterm (<37 weeks) pre-eclampsia	1091	0.23	0.44
SGA†	25322	5.9	8.2
Maternal characteristics
Year of first birth
1990–94	184949	40.9	57.1
1995–99	135594	30.7	32.5
2000–06	119779	28.4	10.4
Interpregnancy interval (years)*
<1	82500	20	2.3
1–3.9	302760	71.6	31
4–6.9	40848	7.2	37
7–9.9	10453	1	20.5
>10	3567	0.2	9.2
Data missing	194
Age second delivery (years)*
<25	58938	12.9	19.7
25–29.9	163269	37.2	35.8
30–34.9	158168	36.4	29.4
>35	59947	13.5	15
Body mass index second pregnancy*
<18.5	9519	2.2	2.2
18.5–24.9	240089	54.7	52.4
>25	123731	27.9	30.8
Data missing	66983	15.3	14.6
Height (cm)*
<162	87443	19.7	21.6
162–171	250495	56.9	57.2
>172	92890	21.1	19.4
Data missing	9494	2.2	1.8
Smoking habits second pregnancy*
Non-smoker	370797	85.6	65.7
Smoker	43965	8.6	28.2
Data missing	25560	5.8	6.1
Involuntary childlessness second pregnancy (years)*
<1	422561	96	94.9
1–2	11943	2.7	3.4
>3	5351	1.2	1.7
Data missing	467	0	0
Mother's country of birth*
Nordic	389279	88.2	91.8
Non-Nordic	47213	10.9	7.7
Data missing	3830	0.9	0.5
Education (years)*
<13	128533	27.5	52.5
13–14	175222	40.2	33.8
>15	101778	24.1	10.1
Data missing	34789	8.2	3.6
Total	440322	409922 (93.1%)	30400 (6.9%)

Pregnancies with unknown information on partner change (n=6137) are excluded from this table.

The total population when calculating rates of small for gestational age (SGA) was 415 922 since the population was restricted to live births and pregnancies with pre-eclampsia or missing information on the infant's weight were excluded.

*p<0.0001.

†SGA, small for gestational age, was defined as a birth weight at or below the 10th percentile for the mean birth weight for gestational age according to the sex specific Swedish fetal growth curve.²⁴