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Aim: To reassess the normal duration of each stage of labor in a contemporary Japanese cohort, and to determine whether prolongation of each stage of labor increases the rate of postpartum hemorrhage (PPH) in vaginal deliveries. Methods: Clinical data of women who delivered at term at 12 facilities between 2012 and 2018 were retrospectively collected. A total of 31 758 women were subdivided into three or four subgroups according to the duration of each stage of labor and parity. Univariate and multivariate logistic regression analyses were performed to estimate crude and adjusted odds ratios (ORs) of PPH (blood loss ≥ 1000 mL) in each subgroup, with women with the shortest durations in each subgroup used as the reference group. Results: The reference range of each stage of labor was found to be shorter than that previously reported. Women with prolonged second (primiparity, adjusted OR: 1.15–1.78; multiparity, adjusted OR: 1.14–1.74) and third (primiparity, adjusted OR: 1.39–4.95; multiparity, adjusted OR: 1.46–3.80) stages of labor showed an increased risk of PPH, whereas those with prolonged first stage did not. A significantly increased risk of PPH was found both in primiparous and multiparous women with third stages of labor ≥ 5 min. Conclusions: The normal duration of each stage of labor in the Japanese population needs to be revised and well-recognized by obstetric care providers. A prolonged third stage of labor was a more important contributing factor to PPH than prolonged first or second stages.

Objectives: We aimed to evaluate the impact of hypertensive disorders of pregnancy (HDP) on short- and medium-term respiratory outcomes in extremely and very preterm infants using the Neonatal Research Network of Japan database. Study design: This was a population-based retrospective study of preterm infants weighing≤1500g born between 22 and 31weeks of gestation between 2003 and 2017. After 1:1 stratification matching by four factors (maternal age, gestational age, parity, and year of delivery), a total of 5137 infants in each group (HDP and non-HDP groups) were selected. Main outcome measures: The association between HDP and various respiratory outcomes was evaluated using univariate and multivariate logistic regression analyses. Results: In the multivariate analyses, HDP was associated with higher odds for respiratory distress syndrome (RDS) (odds ratio 1.83, 95% confidence interval [1.65–2.03]), but reduced odds of persistent pulmonary hypertension of the newborn (PPHN) (0.34 [0.26–0.46]) and inhaled nitric oxide use (0.43 [0.33–0.55]). Although HDP was associated with an increased risk of chronic lung disease (CLD) in the univariate analysis, this association was not significant after adjustment for covariates (0.94 [0.83–1.07]). No significant association was found between HDP and home oxygen therapy (HOT) and medium-term oxygen use. Conclusion: The impact of maternal HDP largely differed depending on respiratory disorders and respiratory support. HDP was associated with higher odds of RDS but reduced odds of PPHN. The risks for CLD, HOT, and medium-term respiratory outcomes in the HDP group were comparable to those in the non-HDP group.

Objectives: To determine the trajectories of platelet counts and the prevalence of gestational thrombocytopenia (<150 × 10^9/L) during normal pregnancies and pregnancies with complications, such as hypertensive disorders of pregnancy (HDP), preeclampsia, and fetal growth restriction (FGR). Study design: A multicenter retrospective study was conducted using laboratory data on women who delivered term singletons at 11 primary maternity care units between 2011 and 2018 (n = 35,045), and non-pregnant women who underwent a medical check-up between 2016 and 2019 (n = 61,189). After 1:1 matching, 28,073 pregnant women and 28,073 non-pregnant women were selected for analysis. Main outcomes measures: The trajectories of platelet counts and prevalence of gestational thrombocytopenia were evaluated in normal pregnant women, pregnant women with complications, and non-pregnant women. Results: The platelet counts declined throughout pregnancy, with the nadir occurring on postpartum day 1. The platelet counts recovered to the level of the non-pregnant state at postpartum 2–7 days. The mean platelet counts at postpartum day 1 decreased by an estimated 19.8% and 9.7% compared to those in the non-pregnant state and first trimester, respectively. The prevalence of gestational thrombocytopenia in normal pregnant women at 37–41 gestational weeks and in pregnant women with complications of HDP, preeclampsia, and FGR were 6.1%, 7.3%, 17.5%, and 7.7%, respectively. Conclusion: Platelet counts declined throughout pregnancy and recovered to the level of the non-pregnant state in the early postpartum period. Gestational thrombocytopenia is common during normal pregnancy, and its prevalence is significantly higher in women with preeclampsia.

Aim: In postpartum women, retained placenta is diagnosed in the absence of signs of placental separation and expulsion, and requires manual removal of the placenta (MROP). MROP may lead to massive hemorrhage, hemodynamic instability, and the need for emergency interventions including blood transfusion, interventional radiology, and hysterectomy. In this study, we aimed to identify the risk factors for retained placenta requiring MROP after vaginal delivery and postpartum hemorrhage (PPH) following MROP. Methods: A multicenter retrospective study was performed using data from women who delivered at term between 2010 and 2018 at 13 facilities in Japan. Of 36 454 eligible women, 112 women who required MROP were identified. Multivariate logistic regression analyses were conducted to evaluate the risk factors for retained placenta and PPH following MROP. Results: A history of abortion, assisted reproductive technology (ART), instrumental delivery, and delivery of small-for-gestational-age infant were independent risk factors for MROP (adjusted odds ratios [95% confidence intervals]: 1.93 [1.28–2.92], 8.41 [5.43–13.05], 1.80 [1.14–2.82], and 4.32 [1.97–9.48], respectively). ART was identified as an independent risk factor for PPH (adjusted odds ratio [95% confidence interval]: 6.67 [2.42–18.36]) in patients who underwent MROP. Conclusion: ART pregnancies significantly increased the risk of retained placenta requiring MROP and PPH. Our results suggest that clinicians need consider patient transfer to a higher-level facility and preparation of sufficient blood products before initiating MROP in cases of ART pregnancies. Our study may assist in identifying high-risk women for PPH before MROP and in guiding treatment decisions, especially in facilities without a blood bank.

Background: Infants born to mothers with hypertensive disorders of pregnancy (HDP) have adverse neurodevelopmental consequences in later life. Magnetic resonance spectroscopy (MRS) is used to predict subsequent neurodevelopment in the field of perinatology. Aim: We aimed to determine whether exposure to HDP in utero leads to alterations in brain metabolites in preterm infants using multi-voxel proton MRS at term-equivalent age. Study design: Retrospective cohort study. Subjects: A total of 103 preterm infants born before 34 weeks of gestation at Nagoya University Hospital between 2010 and 2018 were eligible. Twenty-seven infants were born to mothers with HDP (HDP group), and 76 were born to mothers without HDP (non-HDP group). Outcome measures: The peak area ratios of N-acetylaspartate (NAA)/choline (Cho), NAA/creatine (Cr), and Cho/Cr were evaluated at 10 designated regions of interest (bilateral frontal lobes, basal ganglia, thalami, temporal lobes, and occipital lobes). Results: The peak area ratios of NAA/Cho and NAA/Cr in the bilateral thalami were significantly higher in the HDP group than in the non-HDP group after adjustment for covariates (postmenstrual age at MRS assessment and infant sex). No significant differences were observed in other regions. Preeclampsia, abnormal umbilical artery blood flow, and fetal growth restrictions were significantly associated with increased NAA/Cho and NAA/Cr ratios in the thalami. Conclusions: Based on the evidence that NAA/Cho and NAA/Cr ratios constantly increase with postmenstrual age in normal brain development, exposure to maternal HDP in utero may accelerate brain maturation and increase neuronal activity in preterm infants.

Objectives: To investigate the prevalence and risk factors of labor-onset hypertension (LOH), defined as hypertension first detected during labor among women without hypertension prior to admission for labor. Study design: In this multicenter retrospective study, clinical data of women who delivered vaginally at term between 2012 and 2018 were collected from 12 primary maternity care units. Blood pressure was measured at five time points from admission to 2 h postpartum in a total of 30,129 normotensive women at the last prenatal check-up. LOH was defined as systolic blood pressure (SBP) of ≥ 140 mmHg or diastolic blood pressure (DBP) of ≥ 90 mmHg during the first to fourth stages of labor. Main outcome measures: Multivariate regression analyses were conducted to evaluate the risk factors of LOH and severe LOH (SBP of ≥ 160 mmHg or DBP of ≥ 110 mmHg). Results: Among the 30,129 women, 8,565 (28.4%) presented with LOH and 734 (2.4%) with severe LOH. The prevalence of LOH was the highest at the second stage of labor (21.7%) and decreased rapidly after delivery. The independent risk factors of LOH were maternal age of ≥ 35 years, pre-pregnancy body mass index of ≥ 25 kg/m2, and pregnancy weight gain of ≥ 15 kg. Conclusion: LOH is common, with approximately one in four women experiencing LOH during labor and early postpartum. Meanwhile, severe LOH occurred in 2.4% of the pregnancies. Closer blood pressure monitoring during labor may enable obstetric caregivers to recognize LOH in a timely manner and reduce maternal adverse outcomes, such as eclampsia and stroke.