This was a cross-sectional, descriptive study.
Setting and participant recruitment
This study was carried out between June and December 2019 in Shanghai, one of the largest cities and the economic center of China. The participants were recruited from one of the 3-A-Class specialized hospitals, which is also one of the earliest provincial and municipal maternal and child health centers in China with > 800 beds, 30 wards, and approximately 30,000 births annually (Shanghai First Maternity and Infant Hospital, 2020). Women were recruited for the study during their routine postpartum clinical visits (usually 6–8 weeks postpartum). A convenience sample was used. Eligible women were approached by the researcher and given enough time to think about participation. After informed consent was gained, the researcher guided the women to complete an anonymous electronic questionnaire in Chinese. Eligible participants were 6–8 weeks postpartum with no complications, > 18 years of age, and had a singleton, live birth. To complete the online questionnaire, women needed to be fluent in Mandarin and have access to a mobile phone. Women with a gestational age < 28 weeks or a neonate weighing < 1500 g were excluded.
Variable and measurements
Sociodemographic characteristics were collected from the participants, and included questions on age (< 35 or ≥ 35 years), household registration location (Shanghai, non-Shanghai), ethnicity (Han or non-Han), education level (primary, secondary, bachelor, or master or above), employment (unemployed/housewife or employed), the only child (yes or no), cigarette smoking (yes or no), and sleep quality (low, medium, or high), and social support.
For use in a busy clinical setting in this study, a single question was adapted and modified from the Pittsburg Sleep Quality Index (PSQI) to evaluate women’s sleep quality. The question is “How did you feel about your sleep quality in the last month?” and the response options were “low, medium, and high”.
Social support was measured using the Perceived Social Support Scale (PSSS) . The PSSS is a 12-item instrument to assess support from family, friends, relatives, and colleagues. Each item is rated on a 7-point Likert scale ranging from 1(strongly disagree) to 7 (strongly agree). The total score ranges from12–84, with higher scores indicating higher perceived social support. A score between 12 and 36 indicates low support, 37–60 indicates medium support, and 61–84 indicates high support. The Chinese version of PSSS has been tested by Jiang  and was shown to have excellent reliability, with a Cronbach’s α of 0.99. The Cronbach’s α in this study was 0.89.
Pregnancy-related characteristics were collected through the electronic medical records, included parity (primiparous or multiparous), planned pregnancy (yes or no), histories of abnormal pregnancy (yes or no), mode of birth (normal vaginal birth, instrumental birth, or cesarean section). According to the the Maternal Pregnancy Risk Assessment and Management Norms released by the National Health Commission of the People’s Republic of China , histories of abnormal pregnancy including miscarriage ≥3 times, history of preterm birth, perinatal death, birth defects, history of ectopic pregnancy, history of trophoblastic disease, history of previous pregnancy complications and comorbidities. Instrumental birth defined by when vaccum extractor or delivery forceps were used, and cesarean section included both planned cesarean section and emergency cesarean section. An emergency cesarean section was performed when there is a situation that immediately threatens the life of the mother or fetus. In this study setting, medical indications for emergency cesarean section included hemorrhage due to placenta praevia, placental abruption, acute fetal distress, amniotic fluid embolism, umbilical cord prolapse, uterine rupture, etc.
Newborn-related characteristics were collected from the electronic medical records, and included baby gender (boy or girl), weight of the neonate (low birthweight: 1500 g–2499 g, normal birthweight: 2500 g–3999 g, or fetal macrosomia: ≥4000 g), gestational age (preterm: 28–36+ 6 weeks, full term: 37–41+ 6 weeks, or postdates ≥42 weeks), newborn’s Apgar score in 1 min (0–3: severe asphyxia, 4–7: mild asphyxia, 8–10: no asphyxia), Apgar score in 5 min (0–3, severe asphyxia, 4–7, mild asphyxia, 8–10, no asphyxia), NICU admission (yes or no), incubator admission (yes or no), and diagnosis of hyperbilirubinemia (yes or no).
Both PPD and PP-PTSD were collected through self-reported questionnaires.
Symptoms of PPD were measured with the Edinburgh Postnatal Depression Scale (EPDS), the most widely used tool for identifying possible PPD and has been recommended by the American College of Obstetricians and Gynecologists (ACOG) and the American Academy of Pediatrics (AAP) . The EPDS is a 10-item, self-report instrument, first published by Cox et al., [39, 40] and translated into over 60 languages. Each item of EPDS is rated on 4-point range from 0 (no, not at all) to 3 (yes, most of the time), and the total score ranges from 0 to 30, with higher scores indicating greater severity of symptoms. We used the Chinese version of the EPDS, which has been validated in Chinese parturients with reliability and validity , and the Cronbach’s α for EPDS in the current study was 0.879. A cut-off score ≥ 13, with sensitivity (86%) and specificity (78%)  was used in this study.
Symptoms of PP-PTSD were measured with the Perinatal Post-traumatic Stress Questionnaire (PPQ). The PPQ is a self-rating scale, developed by DeMier  and based on DSM-IV to identify women suffering from PTSD symptoms at 1–18 months postpartum. The PPQ has 14 items, with each item scoring from 0 (not at all) to 4 (often for more than 1 month). The total score ranges from 0 to 56, with a score ≥ 19 indicating that PP-PTSD symptoms exist. The reliability and validity of the Chinese version of the PPQ were tested by Zhang  with a Cronbach’s α of 0.84; the test-retest reliability was 0.88. The Cronbach’s α in this study was 0.83.
Procedure and ethical consideration
Ethical approval for the study was obtain from the hospital Ethics Committee. Researchers approached potential participants and gave a brief introduction of the study (research purpose, potential impact, and participants’ rights). Women were informed that their participation was entirely voluntary, and whether they agreed to participate or not did not impact their treatment. Informed consent was obtained from participants at the beginning of the online questionnaire. All participants were assured that their data would be kept confidential and only accessed by the researcher.
Data were analyzed using the Statistical Package for Social Sciences (SPSS, version 22.0 for Windows). Scores of EPDS and PPQ are presented as the mean (M) and standard deviation (SD). To facilitate statistical analysis and interpretation of the results, the PSSS, EPDS, and PPQ scores were converted into categorical variables. Frequencies and percentages are presented for all categorical variables. A chi-square test and logistic regression analysis were performed to evaluate the association of factors related to PPD and PP-PTSD. Variables were included into the multivariate logistic regression model if the variables had a significant association (P ≤ 0.20) by the χ2 test or deemed important enough clinically, despite no statistical significance. All statistics were performed using two-sided tests, and the significance level was set at a P < 0.05.