Proefschrift

112 5 CHAPTER 5 4 | GOODARZI et al. the whole study population. Statistical analyses were conducted using STATA software.22 3 | RESULTS 3.1 | Study population characteristics and trend analyses 2000-2018 For the study period 2000-2018, Perined contained data of 3 700 336 pregnancies. After applying the exclusion criteria, 1 734 139 pregnancies of healthy women remained for the trend analyses (Figure 1). The trend in TM, FM, and NM rate is shown in Figure 1. The TM rate has declined steadily in the past two decades. The decline was predominantly the result of declining FM, which had almost halved in 2018 compared with 2000. Figures S1–S4 show the trend in TM specified for ethnicity, parity, age, and SES. The TM among nulliparous women and women aged ≥40 years showed the largest decline. In 2000, nulliparous women and women aged ≥40 years had the highest TM rate compared with other parity and age subcategories, 0.3% and 0.64%, respectively. In 2018, the TM rate had declined to 0.13% for nulliparous women, and to 0.16% for women aged ≥40 years, resulting in one of the lowest TM rates compared with other parity and age subcategories. For ethnicity, the TM rate declined among both Dutch and non-Dutch women, but remained overall higher for non-Dutch women. The trend analyses specified by FM and NM showed a similar trend and are therefore not shown. 3.2 | Study population characteristics and sub-analyses 2012-2018 In the study period 2012-2018, Perined contained data of 1 371 362 pregnancies. After applying the exclusion criteria, 603 833 pregnancies of healthy women were included for the analyses (Figure 2). The demographic characteristics of the population are shown in Figure S5. The absolute number of pregnancies and the absolute number of fetal and neonatal deaths decreased with advancing gestational week because only women still pregnant at the onset of the gestational period were included. 3.3 | Descriptive analyses 3.3.1 | Association between single determinants and total mortality Table 1 presents the associations between single maternal characteristics and TM, stratified by gestational week for the years 2012-2018. The TM rate among women pregnant at the start of the gestational period increased F IGURE 2 Study cohort Cohort 2000-2018 total: n = 3,700,336 cases Cohort 2012-2018 total: n = 1,371,362 cases Excluded cases in order of exclusion: (total: n = 1,966,197 cases) - Birth <37 weeks gesta on (n = 303,495 cases) - Missing informa on on gesta onal age (n = 312,342 cases, including 299,206 abor ons) - Mul ple gesta on or missing informa on on mul ple gesta on (n = 57,969 cases) - Primary obstetrical led care (n =365,882 cases) - Referral to obstetrician-led care <37 weeks gesta on (n =458,362 cases) - Congenital malforma ons (n = 29,648) - Registered medical indica ons for referral to obstetrician-led care ≥37 weeks gesta on (n = 438,353 cases) Excluded cases in order of exclusion: (total n = 1,966,197 cases) - Birth <37 weeks gesta on (n = 12,935 cases) - Missing informa on on gesta onal age (n = 176,492 cases, including 173,327 abor ons) - Mul ple gesta on or missing informa on on mul ple gesta on (n = 17,019 cases) - Primary obstetrical led care (n =107,060 cases) - Referral to obstetrician-led care <37 weeks gesta on (n =188,215 cases) - Congenital malforma ons (n = 11,077) - Registered medical indica ons for referral to obstetrician-led care ≥37 weeks gesta on (n = 164,731 cases) Healthy study cohort 2000-2018 total: n = 1,734, 139 cases Healthy study cohort 2012-2018 total: n = 603,833 cases

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