110 5 CHAPTER 5 2 | GOODARZI et al. 1 | INTRODUCTION Maternal characteristics, such as parity and age, are increasingly considered indications for induction of labor (IOL) of healthy women (when we use the term “woman,” we also refer to individuals with a uterus who are not woman identified, including trans and non-binary individuals). Nulliparity and advanced maternal age– generally defined as 35 years or older1–are associated with a higher probability of fetal and neonatal mortality (FM and NM).2,3 To prevent FM and NM, a growing number of healthy nulliparous women and women at advanced age are routinely offered IOL at 39 weeks of gestation.4 Although medically indicated IOL can prevent FM and NM, routine IOL may lead to unnecessary harm to women and their children. IOL is associated with harmful side effects, including suboptimal fetal brain development,5 uterine rupture,6 severe postpartum haemorrhage,7 severe perineal lacerations,8 and negative birth experiences9 due to reduction of choice in care provider and birth place, restricted mobility, and feeling of loss of control.9 A recent study into short-term and long-term outcomes of IOL in a healthy population found that IOL for non-medical reasons was associated with higher birth interventions and adverse maternal, neonatal, and child outcomes.10 Therefore, it is argued that IOL should only be used if the expected benefits of IOL outweigh its potential harms and the disadvantage of waiting for spontaneous onset of labor.11 To fully balance the risks and benefits of IOL for maternal characteristics such as parity and advanced maternal age, and to more accurately identify those births which would benefit from IOL, additional relevant maternal characteristics and gestational age should be taken into account in the risk selection process. Maternal characteristics such as ethnicity12 and socioeconomic status (SES)13 are also associated with an increased probability of FM and NM. Furthermore, the probability of FM and NM differs across the term period.14 Nevertheless, most studies focus on the association between single determinants and FM and NM, and apply statistical adjustments.3,14 The aim of this study is to gain more insight into the association and interaction between maternal characteristics, gestational age, and FM and NM among healthy women giving birth to a single child at term. Therefore, we examined FM and NM rates for each term gestational week, by maternal ethnicity, age, parity, and SES, and for the interaction between these characteristics in a healthy Dutch population. 2 | METHODS 2.1 | Study design In this nationwide longitudinal retrospective cohort study, we used data from the Netherlands Perinatal Registry (Perined). Perined includes data from almost all pregnancies and births in primary midwife-led care, secondary obstetrician-led care and pediatric care.15 Midwives, obstetricians, and pediatricians obtained women's consent for data registration in Perined and the use of their data for research purposes.16 For the purpose of this study, all data were anonymized. We analyzed the data for the years 2000-2018 (19 years) to show the time trend in fetal mortality (FM), neonatal mortality (NM), and total mortality (TM), and performed a sub-analysis for the years 2012- 2018 (7 years), to examine the most recent associations and interactions between single and multiple maternal characteristics and PM. 2.2 | Study population In the Netherlands, healthy women are cared for by independent midwives in primary midwife-led care in community practices. When the risks of adverse outcomes increase or complications develop, women are referred to obstetrician-led care in the hospital. To study TM in a healthy population, we included all singleton pregnancies inmidwife-led care giving birth from 37 weeks of gestation onwards. We excluded cases with missing information on gestational age–including abortions–and multiple gestation, and all cases with a registered medical indication for referral to obstetrician-led care before the onset of labor, including cardiac diseases, respiratory disorders, thromboembolic disorders, hypertensive disorders, diabetes, hematological disorders, neurological disorders, gynecological diseases, use of medicines, drugs or alcohol, blood group antagonism, lethal fetal congenital malformations, cervical insufficiency, caesarean section, infection, fetal heart arrhythmia, suspected fetal growth restriction, suspected macrosomia, non-cephalic presentation, placenta previa, and lack of antenatal care (Figure 1). K E YWO R D S age, decision-making, ethnicity, induction of labor, maternal characteristics, parity, risk, risk selection, socioeconomic status