Ling Huang

Dalhousie University, Halifax, Nova Scotia, Canada

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Publications (6)28.57 Total impact

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    ABSTRACT: We assessed temporal trends in birth asphyxia in Canada, to determine whether changes were real or secondary to changes in coding. We used data from the Canadian Institute for Health Information Discharge Abstract Database to study the national incidence of birth asphyxia, by using International Classification of Diseases codes. We also studied birth asphyxia by using data from the Nova Scotia Atlee Perinatal Database. In the Nova Scotia Atlee Perinatal Database, we defined a case of birth asphyxia as a live birth with an Apgar score at 5 minutes of < or =3, depression at birth requiring resuscitation with a mask for > or =3 minutes and/or intubation, or neonatal postasphyctic seizures. Nationally, between 1991 and 2005, the incidence of birth asphyxia decreased significantly, from 43.8 to 2.4 cases per 1000 live births. The rate of decrease was highest between 1991 and 1998, corresponding to a period when strict Canadian and international criteria for the diagnosis of birth asphyxia were published. By comparison, neither national rates of related diagnoses nor Nova Scotia birth asphyxia rates, which ranged from 8.8 to 14.3 cases per 1000 live births, showed evidence of a decrease during the study period. Comparisons of national trends in birth asphyxia diagnoses and trends in conditions associated with birth asphyxia, both nationally and in Nova Scotia, suggest that the dramatic decrease in the diagnosis of birth asphyxia is an artifact of changes in the use of International Classification of Diseases coding associated with the publication of stricter diagnostic definitions of birth asphyxia. We conclude that International Classification of Diseases codes are not useful for surveillance of birth asphyxia.
    PEDIATRICS 05/2009; 123(4):e668-72. · 4.47 Impact Factor
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    ABSTRACT: The number of women who delay childbirth to their late 30s and beyond has increased significantly over the past several decades. Studies regarding the relation between older maternal age and the risk of stillbirth have yielded inconsistent conclusions. In this systematic review we explored whether older maternal age is associated with an increased risk of stillbirth. We searched MEDLINE, EMBASE and the Cochrane Database of Systematic Reviews for all relevant articles (original studies and systematic reviews) published up to Dec. 31, 2006. We included all cohort and case-control studies that measured the association between maternal age and risk of stillbirth. Two reviewers independently abstracted data from all included studies using a standardized data abstraction form. Methodologic and statistical heterogeneities were reviewed and tested. We identified 913 unique citations, of which 31 retrospective cohort and 6 case-control studies met our inclusion criteria. In 24 (77%) of the 31 cohort studies and all 6 of the case-control studies, we found that greater maternal age was significantly associated with an increased risk of stillbirth; relative risks varied from 1.20 to 4.53 for older versus younger women. In the 14 studies that presented adjusted relative risk, we found no extensive change in the direction or magnitude of the relative risk after adjustment. We did not calculate a pooled relative risk because of the extreme methodologic heterogeneity among the individual studies. Women with advanced maternal age have an increased risk of stillbirth. However, the magnitude and mechanisms of the increased risk are not clear, and prospective studies are warranted.
    Canadian Medical Association Journal 02/2008; 178(2):165-72. · 6.47 Impact Factor
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    ABSTRACT: Preterm and postterm birth rates are substantially higher in the United States than in Canada and other industrialized countries, although relative mortality at preterm compared with term gestation is considerably lower. We attempted to explain these differences based on differences in the method of gestational age estimation. We used information on all live births in the United States and Canada for 1995-2002 and on singleton births and perinatal deaths for 1996-1999. Gestational age in Canada was based on the clinical estimate, whereas in the United States both menstrual-based and clinical estimates were used. In 2002, preterm (12.3%) and postterm birth (6.6%) rates in the United States were far higher than in Canada (7.6% and 1.0%, respectively) when U.S. rates were based on menstrual dates. Differences were reduced or abolished when U.S. rates were based on the clinical estimate of gestation (10.1% and 1.0%, respectively). In Canada, the rate ratio for perinatal death at preterm compared with term gestation was 27.8 (95% confidence interval [CI] 26.3-29.3), similar to that in the United States when gestation was based on the clinical estimate (rate ratio 26.5, 95% CI 26.1-26.9, P value for difference in rate ratios=.06) but not when based on menstrual dates (rate ratio 18.9, 95% CI 18.7-19.2, P<.001). Menstrual dates in U.S. data misclassify gestational duration and overestimate both preterm and postterm birth rates. For international comparisons, gestational age in the United States should be based on the clinical estimate. Level of Evidence: II.
    Obstetrics and Gynecology 04/2007; 109(4):813-22. · 4.80 Impact Factor
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    ABSTRACT: Although death rates are often used to monitor the quality of health care, in industrialized countries maternal deaths have become rare. Severe maternal morbidity has therefore been proposed as a supplementary indicator for surveillance of the quality of maternity care. Our purpose in this study was to describe severe maternal morbidity in Canada over a 10-year period, among women with or without major pre-existing conditions. We carried out a retrospective cohort study of severe maternal morbidity involving 2,548,824 women who gave birth in Canadian hospitals between 1991 and 2000. Thirteen conditions that may threaten the life of the mother (e.g., eclampsia) and 11 major pre-existing chronic conditions (e.g., diabetes) that could be identified from diagnostic codes were noted. The overall rate of severe maternal morbidity was 4.38 per 1000 deliveries. The fatality rate among these women was 158 times that of the entire sample. Rates of venous thromboembolism, uterine rupture, adult respiratory distress syndrome, pulmonary edema, myocardial infarction, severe postpartum hemorrhage requiring hysterectomy, and assisted ventilation increased substantially from 1991 to 2000. The presence of major pre-existing conditions increased the risk of severe maternal morbidity to 6-fold. Severe maternal morbidity occurs in about 1 of 250 deliveries in Canada, with marked recent increases in certain morbid conditions such as pulmonary edema, myocardial infarction, hemorrhage requiring hysterectomy, and the use of assisted ventilation.
    Canadian Medical Association Journal 10/2005; 173(7):759-64. · 6.47 Impact Factor
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    ABSTRACT: The purpose of this study was to examine the association between intrapair birthweight discordance and fetal and neonatal mortality. This was a historical cohort study, using the Statistics Canada linked birth-infant death file. Twin births in Canada (excluding Ontario) for the period 1986-1997 were studied. Outcome measures were fetal and neonatal mortality. Among 59,034 twin births, 53% had 0 to 9% birthweight difference; 30% had 10 to 19% discordance; 11% had 20 to 29% discordance; and 6% had > or = 30% discordance. Maternal age, parity, sex discordance, and gestational age were important factors affecting birth weight discordance. Fetal death rates were 0.95, 1.26, 3.14, and 11.10%, respectively, in infants with a birthweight discordance of 0 to 9, 10 to 19, 20 to 29, and > or = 30%. Corresponding figures for neonatal death rates were 1.90, 2.32, 3.05, and 8.86%, respectively. Adjustment for important confounding variables including the actual birthweight and gestational age substantially reduced the birthweight discordance-related risk of fetal and neonatal mortality, but the results remained statistically significant and clinically important. The birthweight discordance-related risk of fetal and neonatal mortality was higher in smaller twins than in larger twins and higher in infants with gestational age > or = 37 weeks than those < 37 weeks. Birthweight discordance is an important risk factor for fetal and neonatal mortality, and the birthweight discordance-related risk of fetal and neonatal mortality is higher in smaller twins than in larger twins and higher in term twins than in preterm twins.
    American Journal of Perinatology 07/2005; 22(5):279-86. · 1.57 Impact Factor
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    ABSTRACT: To determine whether cesarean and operative vaginal deliveries are associated with an increased risk of maternal rehospitalization compared with spontaneous vaginal delivery. A population-based cohort study was conducted by using the Canadian Institute for Health Information's Discharge Abstract Database between 1997/1998 and 2000/2001, which included 900,108 women aged 15-44 years with singleton live births (after excluding several selected obstetric conditions). A total of 16,404 women (1.8%) were rehospitalized within 60 days after initial discharge. Compared with spontaneous vaginal delivery (rate 1.5%), cesarean delivery was associated with a significantly increased risk of postpartum readmission (rate 2.7%, odds ratio [OR] 1.9, 95% confidence interval [CI] 1.8-1.9); ie, there was 1 excess postpartum readmission per 75 cesarean deliveries. Diagnoses associated with significantly increased risks of readmission after cesarean delivery (compared with spontaneous vaginal delivery) included pelvic injury/wounds (rate 0.86% versus 0.06%, OR 13.4, 95% CI 12.0-15.0), obstetric complications (rate 0.23% versus 0.08%, OR 3.0, 95% CI 2.6-3.5), venous disorders and thromboembolism (rate 0.07% versus 0.03%, OR 2.7, 95% CI 2.1-3.4), and major puerperal infection (rate 0.45% versus 0.27%, OR 1.8, 95% CI 1.6-1.9). Women delivered by forceps or vacuum were also at an increased risk of readmission (rates 2.2% and 1.8% versus 1.5%; OR forceps: 1.4, 95% CI 1.3-1.5; OR vacuum: 1.2, 95% CI 1.2-1.3, respectively). Higher readmission rates after operative vaginal delivery were due to pelvic injury/wounds, genitourinary conditions, obstetric complications, postpartum hemorrhage, and major puerperal infection. Compared with spontaneous vaginal delivery, cesarean delivery, and operative vaginal delivery increase the risk of maternal postpartum readmission. II-2.
    Obstetrics and Gynecology 05/2005; 105(4):836-42. · 4.80 Impact Factor

Publication Stats

224 Citations
28.57 Total Impact Points

Institutions

  • 2007
    • Dalhousie University
      • Department of Obstetrics and Gynaecology
      Halifax, Nova Scotia, Canada
  • 2005
    • University of Ottawa
      • Department of Obstetrics and Gynecology
      Ottawa, Ontario, Canada
    • Health Canada
      Ottawa, Ontario, Canada