Second trimester hyperemesis gravidarum is associated with increased risk of preterm pre-eclampsia, placental abruption and small for gestational age birth
- Correspondence to: Dr Angela Wood, Carson-Newman University, Nursing, 1646 Russell Avenue, Jefferson City, TN, 37760, USA;
Implications for practice and research
Patients experiencing late onset hyperemesis gravidarum (HG) and placental dysfunction disorders (PDD) should be closely monitored for disorders associated with abnormal placentation, including pre-eclampsia (PE), placental abruption and delayed intrauterine growth.
In addition, research is needed to study the potential effects of low-dose aspirin and increased blood pressure surveillance on the outcome of pregnancy in these patients.
While the incidence of HG is only 0.3–2%, the associated severe nausea and vomiting frequently lead to dehydration, malnutrition and hospitalisation.1 Aetiology of HG is unclear, although most researchers consider the hormonal changes to be at least partly responsible. This study has an interesting hypothesis: that the time of appearance of HG could affect the outcome of pregnancy. The justification for this approach is related to the idea that abnormal placentation and the resultant changes in the human chorionic gonadotropin (hCG) levels may be related to the time of HG presentation. Bolin and colleagues looked for an association between the time of onset of HG and the development of pregnancy complications associated with PDD, including small for gestational age (SGA) infants, PE, placental abruption and stillbirth.
Retrospective data were collected from the Swedish Medical Birth Register on all women who delivered between 1997 and 2009. The study sample consisted of 12 270 women who were admitted to the hospital with a diagnosis of HG before 22 weeks gestation. This group was divided into those admitted to the hospital before and after 12 completed weeks of gestation. ORs with 95% CIs were estimated for PDD in women with HG using women without the diagnosis as a reference. The risks were adjusted for numerous demographic and health variables.
As hypothesised, based on the pathogenesis of abnormal placentation, differences were found in the outcome of pregnancy depending on when HG developed. In pregnancies where the HG diagnosis was made after 12 weeks gestation, there was a strong association of development of PE, twofold over patients without HG, and placental abruption, threefold over patients without HG. In addition, HG was not found to be associated with the occurrence of stillborn infants.
Demographic differences were noted between patients with early-onset and those with late-onset HG. When compared with mothers diagnosed after 12 weeks, mothers who were diagnosed in the first 12 weeks of pregnancy were found to be older, to have had previous multiple pregnancies, to be of normal weight, to be non-smokers and to be carrying a female fetus.
HG and its associated complications are a significant danger during the childbearing period. The unique use of pathophysiological insight to develop the independent variables of early-onset and late-onset HG provides an interesting and useful approach to the care of these women. The association between late-onset HG and PDD provides a strong indication for increased assessment for development of adverse outcomes of pregnancy, especially placental abruption and the development of PE resulting in preterm delivery.
The findings of this study raise many questions concerning the role of hCG in the development of HG, PE, SGA and abnormal placentation and abruption. Future studies may want to focus on hCG levels in the first and second trimesters along with increased vigilance in the assessment of placental development, implantation and function.
The large sample size adds strength to the study findings and allows for assessment of numerous demographic and health variables. However, a criticism of this study is that the authors claim that the data were collected prospectively. A prospective study is one where ‘the independent variable is identified at the present time, and then subjects are followed in the future to observe the dependent variable’.2 This study was conducted retrospectively, using the data collected over several years. The disadvantage is that potentially significant data, including maternal diet, weight gain, true onset of HG and the onset of PE were not collected. Future prospective studies should include this data.
Overall, this is an important study with findings that may affect the management of patients with HG, especially those who experience onset in the second trimester.