02. tbl. 109. árg. 2023
Preterm birth among Icelandic and migrant women in Iceland during 1997-2018 and main contributing factors
Embla Ýr Guðmundsdóttir1,2
Lilja Vigfúsdóttir3
Helga Gottfreðsdóttir1,4
1Department of Midwifery, Faculty of Nursing and Midwifery, University of Iceland, Iceland, 2The Reykjavík Birth Center, Iceland, 3The Health Directorate of East Iceland, Iceland, 4Department of Obstetrics and Gynecology, Women´s Clinic, Landspítali University Hospital, Iceland.
Correspondence: Embla Ýr Guðmundsdóttir, emblayrg@gmail.com
Key words: preterm birth, migrant women, risk factors, antenatal care.
INTRODUCTION: Migrant women often experience worse perinatal outcomes during pregnancy, birth, and puerperium than native women, but results regarding preterm birth vary. The objective of this study was to detect the prevalence and risk factors of preterm birth among Icelandic and migrant women in Iceland.
MATERIAL AND METHODS: The study was a population-based cohort study with data from the Icelandic Medical Birth Register. The cohort included all women who had a singleton birth from 22w0d to 36w6d of pregnancy in the years 1997-2018, a total of 89 170 women. The group was divided in two; women with an Icelandic citizenship and women with foreign citizenship, that were further divided according to the Human Development Index (HDI) of their country of citizenship. Preterm birth rate and risk factor prevalence was analysed according to this classification and significance in differences measured with a chi-square test.
RESULTS: Significance in differences of preterm birth was found between Icelandic (4.4%) and migrant women (5.6%) (p<0.001). Migrant women from middle-HDI countries gave birth preterm in 5.5% of cases (p<0.01) and women from low-HDI countries in 6.4% of cases (p<0.001). Migrant women were more often diagnosed with urinary tract infections, diabetes, intrauterine growth restriction and premature rupture of membranes, but less often with pre-eclampsia, obesity, placental defect, mental health issues and age <18 years (p<0.05).
CONCLUSION: Migrant women in Iceland from middle-HDI and low-HDI countries give birth preterm more often than Icelandic women. A difference in risk factors is also present and needs further research. The findings can be used in continuing development of prenatal care for migrant women in Iceland.
Table I. Background variables of women who gave birth prematue in Iceland during 1997-2018.
Total (n=4021) | Icelandic (n=3582) |
Migrant (n=439) |
High HDI ≥0.900 (n=83) | Middle HDI 0.850-0.899 (n=218) | Low HDI ≤0.849 (n=115) | |||||||||||
n | % | n | % | n | % | p | n | % | p | n | % | p | n | % | p | |
Marital status | ||||||||||||||||
Married/ cohabiting | 1466 | 36.5 | 1261 | 35.2 | 205 | 62.9 | <0.001 | 29 | 45.3 | 0.094 | 90 | 57.3 | <0.001 | 77 | 82.8 | <0.001 |
Not married/ cohabiting | 2441 | 60.7 | 2320 | 64.8 | 121 | 37.1 | 35 | 54.7 | 67 | 42.7 | 16 | 17.2 | ||||
Missing | 114 | 2.8 | 1 | 0.0 | 113 | 25.7 | 19 | 22.9 | 61 | 28.0 | 22 | 19.1 | ||||
Residence | ||||||||||||||||
Capital area | 2514 | 62.5 | 2258 | 63.0 | 256 | 58.3 | 0.054 | 39 | 47.0 | 0.003 | 134 | 61.5 | 0.641 | 74 | 64.3 | 0.774 |
Rural | 1507 | 37.5 | 1324 | 37.0 | 183 | 41.7 | 44 | 53.0 | 84 | 38.5 | 41 | 35.7 | ||||
Missing | 0 | 0.0 | 0 | 0.0 | 0 | 0.0 | 0 | 0.0 | 0 | 0.0 | 0 | 0.0 | ||||
Employment | ||||||||||||||||
Employed/ student | 3402 | 84.6 | 3067 | 85.6 | 335 | 76.3 | <0.001 | 61 | 73.5 | 0.002 | 174 | 79.8 | 0.019 | 88 | 76.5 | 0.007 |
Not employed/ student | 619 | 15.4 | 515 | 14.4 | 104 | 23.7 | 22 | 26.5 | 44 | 20.2 | 27 | 23.5 | ||||
Missing | 0 | 0.0 | 0 | 0.0 | 0 | 0.0 | 0 | 0.0 | 0 | 0.0 | 0 | 0.0 | ||||
Parity | ||||||||||||||||
Primipara | 2014 | 50.1 | 1745 | 49.0 | 260 | 59.2 | <0.001 | 44 | 53.0 | 0.466 | 134 | 61.5 | <0.001 | 67 | 58.3 | 0.050 |
Multipara | 2007 | 49.9 | 1828 | 51.0 | 179 | 40.8 | 39 | 47.0 | 84 | 38.5 | 48 | 41.7 | ||||
1 | 1068 | 26.6 | 945 | 26.4 | 123 | 28.0 | <0.001 | 22 | 26.5 | 0.799 | 64 | 29.4 | <0.001 | 32 | 27.8 | 0.040 |
2 | 621 | 15.4 | 578 | 16.1 | 43 | 9.8 | 12 | 14.5 | 17 | 7.8 | 13 | 11.3 | ||||
3+ | 318 | 7.9 | 305 | 8.5 | 13 | 3.0 | 5 | 6.0 | 3 | 1.4 | 3 | 2.6 | ||||
Missing | 0 | 0.0 | 0 | 0.0 | 0 | 0.0 | 0 | 0.0 | 0 | 0.0 | 0 | 0.0 | ||||
Age | ||||||||||||||||
≤20 years | 294 | 7.3 | 273 | 7.6 | 21 | 4.9 | 0.151 | 4 | 4.8 | 0.080 | 14 | 6.4 | 0.902 | 2 | 1.7 | 0.073 |
21-29 years | 1917 | 47.8 | 1714 | 47.9 | 203 | 47.1 | 31 | 37.3 | 108 | 49.5 | 57 | 49.6 | ||||
30-39 years | 1629 | 40.6 | 1440 | 40.2 | 189 | 43.9 | 45 | 54.2 | 86 | 39.4 | 53 | 46.1 | ||||
≥40 years | 173 | 4.3 | 155 | 4.3 | 18 | 4.2 | 3 | 3.6 | 10 | 4.6 | 3 | 2.6 | ||||
Missing | 8 | 0.2 | 0 | 0.0 | 8 | 1.8 | 0 | 0.0 | 0 | 0.0 | 0 | 0.0 | ||||
Onset of labor | ||||||||||||||||
Spontaneous | 2611 | 64.9 | 2309 | 64.5 | 302 | 68.8 | 0.073 | 47 | 56.6 | 0.141 | 156 | 71.6 | 0.033 | 85 | 73.9 | 0.037 |
Induction | 976 | 24.3 | 879 | 24.5 | 97 | 22.1 | 0.260 | 17 | 20.5 | 0.395 | 58 | 26.6 | 0.492 | 19 | 16.5 | 0.048 |
Elective caesarean section | 512 | 12.7 | 462 | 12.9 | 50 | 11.5 | 0.371 | 11 | 13.3 | 0.924 | 28 | 12.8 | 0.982 | 10 | 8.7 | 0.184 |
Number of antenatal care visits | ||||||||||||||||
0 | 44 | 1.1 | 21 | 0.6 | 23 | 5.2 | <0.001 | 10 | 12.0 | <0.001 | 3 | 1.4 | 0.005 | 4 | 3.5 | <0.001 |
1 to 3 | 238 | 5.9 | 201 | 5.6 | 37 | 8.4 | 6 | 7.2 | 18 | 8.3 | 12 | 10.4 | ||||
4 to 8 | 2512 | 62.5 | 2225 | 62.1 | 287 | 65.4 | 53 | 63.9 | 150 | 68.8 | 73 | 63.5 | ||||
More than 8 | 1226 | 30.5 | 1134 | 31.7 | 92 | 21.0 | 14 | 16.9 | 47 | 21.6 | 26 | 22.6 | ||||
Missing | 1 | 0.0 | 1 | 0.0 | 0 | 0.0 | 0 | 0.0 | 0 | 0.0 | 0 | 0.0 |
The citizenship of 23 women was not recorded and therefore they do not fall under the HDI classification. However they were analyzed under the category "migrant women".
p-values are for comparison of each group of migrant women with the group of Icelandic women, x2
Table II. Prevalence of singleton premature births in Iceland during 1997-2018.
Total (n=89170) |
Icelandic (n=81350) |
Migrant (n=7820) |
High HDI ≥0.900 (n=1771)
|
Middle HDI 0.850-0.899 (n=3928)
|
Low HDI ≤0.849 (n=1796) | |||||||||||
n | % | n | % | n | % | p | n | % | p | n | % | p | n | % | p | |
Preterm birth total | 4021 | 4.5 | 3582 | 4.4 | 439 | 5.6 | <0.001 | 83 | 4.7 | 0.565 | 218 | 5.5 | 0.001 | 115 | 6.4 | <0.001 |
Missing | 3558 | 3.9 | 2895 | 3.4 | 338 | 4.1 | 76 | 4.1 | 147 | 3.6 | 90 | 4.8 | ||||
Extremely preterm <28 weeks |
276 | 0.3 | 243 | 0.3 | 33 | 0.4 | 0.061 | 6 | 0.3 | 0.760 | 16 | 0.4 | 0.227 | 9 | 0.5 | 0.123 |
Very preterm 28w0d-31w6d |
397 | 0.4 | 355 | 0.4 | 42 | 0.5 | 0.218 | 9 | 0.5 | 0.666 | 19 | 0.5 | 0.667 | 11 | 0.6 | 0.285 |
Moderate to late preterm 32w0d-36w6d | 3348 | 3.8 | 2984 | 3.7 | 364 | 4.7 | <0.001 | 68 | 3.8 | 0.704 | 183 | 4.7 | 0.001 | 95 | 5.3 | <0.001 |
Table III. Prevalence of risk factors in women who gave birth to a singleton prematurely in Iceland during 1997-2018.
Total (n=4021) |
Icelandic (n=3582) |
Migrant (n=439) |
High HDI ≥0.900 (n=83)
|
Middle HDI 0.850-0.899 (n=218)
|
Low HDI ≤0.849 (n=115)
|
|||||||||||
n | % | n | % | n | % | p | n | % | p | n | % | p | n | % | p | |
Urinary tract infectionᵃ | 6 | 0.1 | 4 | 0.1 | 2 | 0.5 | 0.133 | 0 | 0.0 | 1.000 | 2 | 0.9 | 0.042 | 0 | 0.0 | 1.000 |
Infection of amniotic sac and membraneᵃ | 66 | 1.6 | 58 | 1.6 | 8 | 1.8 | 0.752 | 0 | 0.0 | 0.642 | 6 | 2.8 | 0.181 | 1 | 0.9 | 1.000 |
Sexually transmitted diseasesᵃ | 14 | 0.3 | 13 | 0.4 | 1 | 0.2 | 1.000 | 0 | 0.0 | 1.000 | 0 | 0.0 | 1.000 | 1 | 0.9 | 0.358 |
Cervical incompetenceᵃ | 7 | 0.2 | 6 | 0.2 | 1 | 0.2 | 0.555 | 0 | 0.0 | 1.000 | 1 | 0.5 | 0.339 | 0 | 0.0 | 1.000 |
Preeclampsia | 643 | 16.0 | 590 | 16.5 | 53 | 12.1 | 0.018 | 8 | 9.6 | 0.096 | 30 | 13.8 | 0.293 | 10 | 8.7 | 0.026 |
Hypertensionᵃ | 159 | 4.0 | 149 | 4.2 | 10 | 2.3 | 0.056 | 1 | 1.2 | 0.261 | 8 | 3.7 | 0.724 | 1 | 0.9 | 0.09 |
Diabetes | 348 | 8.7 | 301 | 8.4 | 47 | 10.7 | 0.105 | 4 | 4.8 | 0.243 | 23 | 10.6 | 0.270 | 19 | 16.5 | 0.002 |
Anemiaᵃ | 88 | 2.2 | 84 | 2.3 | 4 | 0.9 | 0.053 | 1 | 1.2 | 1.000 | 1 | 0.5 | 0.092 | 2 | 1.7 | 1.000 |
Obesityᵃ | 194 | 4.8 | 182 | 5.1 | 12 | 2.7 | 0.030 | 2 | 2.4 | 0.440 | 8 | 3.7 | 0.353 | 0 | 0 | 0.007 |
Placental disorder | 246 | 6.1 | 226 | 6.3 | 20 | 4.6 | 0.148 | 6 | 7.2 | 0.734 | 6 | 2.8 | 0.033 | 7 | 6.1 | 0.923 |
In vitro fertilizationᵃ | 71 | 1.8 | 63 | 1.8 | 8 | 1.8 | 0.924 | 2 | 2.4 | 0.659 | 4 | 1.8 | 0.793 | 2 | 1.7 | 1.000 |
Preterm labor without deliveryᵃ | 71 | 1.8 | 63 | 1.8 | 8 | 1.8 | 0.924 | 2 | 2.4 | 0.659 | 4 | 1.8 | 0.793 | 2 | 1.7 | 1.000 |
Premature rupture of membranes | 1124 | 28.0 | 977 | 27.3 | 147 | 33.5 | 0.006 | 30 | 36.1 | 0.074 | 73 | 33.5 | 0.046 | 40 | 34.8 | 0.076 |
Mental disordersᵃ | 42 | 1.0 | 42 | 1.2 | 0 | 0.0 | 0.012 | 0 | 0.0 | 1.000 | 0 | 0.0 | 0.172 | 0 | 0.0 | 0.641 |
Polyhydroamnionᵃ | 107 | 2.7 | 96 | 2.7 | 11 | 2.5 | 0.830 | 2 | 2.4 | 1.000 | 4 | 1.8 | 0.449 | 5 | 4.3 | 0.244 |
Low birth weight | 484 | 12.0 | 422 | 11.8 | 62 | 14.1 | 0.155 | 11 | 13.3 | 0.681 | 36 | 16.5 | 0.037 | 12 | 10.4 | 0.659 |
Supervision of high-risk pregnancyᵃ | 100 | 2.5 | 93 | 2.6 | 7 | 1.6 | 0.203 | 1 | 1.2 | 0.724 | 3 | 1.4 | 0.265 | 3 | 2.6 | 1.000 |
Substance abuse | 11 | 0.3 | 11 | 0.3 | 0 | 0.0 | 0.622 | 0 | 0.0 | 1.000 | 0 | 0.0 | 1.000 | 0 | 0.0 | 1.000 |
Liver and biliary tract disordersᵃ | 86 | 2.1 | 77 | 2.1 | 9 | 2.1 | 0.892 | 0 | 0.0 | 0.421 | 5 | 2.3 | 0.810 | 4 | 3.5 | 0.319 |
Fetal stress | 460 | 11.4 | 409 | 11.4 | 51 | 11.6 | 0.902 | 9 | 10.8 | 0.871 | 32 | 14.7 | 0.144 | 9 | 7.8 | 0.231 |
Stillbirthᵃ | 182 | 4.5 | 164 | 4.6 | 18 | 4.1 | 0.649 | 4 | 4.8 | 0.791 | 8 | 3.7 | 0.531 | 5 | 4.3 | 0.907 |
Maternal age <18 yearsᵃ | 41 | 1.0 | 41 | 1.1 | 0 | 0.0 | 0.019 | 0 | 0.0 | 1.000 | 0 | 0.0 | 0.170 | 0 | 0.0 | 0.638 |
Maternal age >40 yearsᵃ | 122 | 3.0 | 110 | 3.1 | 12 | 2.7 | 0.697 | 3 | 3.6 | 0.742 | 5 | 2.3 | 0.515 | 3 | 2.6 | 0.319 |
The citizenship of 23 women was not recorded and therefore they do not fall under the HDI classification. However, they were analyzed under the category "migrant women".
ᵃ If Chi-square tests were not valid due to >20% cells having an expected cound <5, the Fisher exact test was used