In the news this month……


Increasingly hypertensive disorders of pregnancy are associated with adverse long-term maternal outcomes and adverse outcomes for the offspring. In their study, Magnus et al seek to clarify whether an association exists between pre-eclampsia and childhood asthma.1 Correctly, they identify that none of the previous studies have performed a formal mediation analysis of preterm birth. The researchers examined the association between pre-eclampsia and asthma at 7 years using national registries, including all births in Norway from 1999 to 2006 (n=406 ,907), and a subsample of children in the Norwegian Mother and Child Cohort Study (n=45,028).

A mediation analysis of preterm birth was performed including a sibling comparison to evaluate unobserved confounding. There was a positive association between pre-eclampsia and asthma in the registry study, with an adjusted relative risk of 1.31 (95% CI 1.22-1.41). This positive association was not observed in the Mother and Child Cohort Study, which had an adjusted relative risk of 1.19 (95% CI 0.99-1.44).

The odds ratios for the direct effect not mediated through preterm birth and the indirect effect in the registry linkage were 1.19 (95% CI 1.10-1.29) and 1.12 (95% CI 1.11-1.14), respectively. The sibling comparison indicated no association between pre-eclampsia and asthma (adjusted OR 1.07, 95% CI 0.87-1.33). Overall, this study demonstrated little evidence for an association between pre-eclampsia and childhood asthma. The study highlights the importance of examining differing databases and using different analytical approaches  The associations observed in this study between pre-eclampsia and asthma were weak and largely explained by pre-term birth and confounders shared by siblings.


Randomised controlled trials such as HYPITAT-II have informed our practice regarding the timing of delivery in women with preterm pre-eclampsia.2 Debate continues regarding the optimal mode of delivery. Levine et al evaluated whether induction, specifically prolonged labour, was associated with adverse maternal outcomes related to pre-eclampsia with severe features and whether Caesarean sections affected the rate.3

The authors conducted a retrospective cohort study of women with pre-eclampsia with severe features ≥34 weeks who were diagnosed either before planned Caesarean or before induction/latent labour. The primary outcome was a composite adverse maternal outcome related to pre-eclampsia with severe features. Pre-eclampsia with severe features was as defined by the Task Force on Hypertension in Pregnancy and included;4 systolic blood pressure of ≥160 mmHg, or diastolic blood pressure ≥110 mmHg on two occasions at least 4 hours apart; thrombocytopenia (platelet count less than 100,000/microliter); Impaired liver function as indicated by abnormally elevated blood concentrations of liver enzymes (to twice normal concentration), severe persistent right upper quadrant or epigastric pain unresponsive to medication and not accounted for by alternative diagnoses, or both; progressive renal insufficiency (serum creatinine concentration greater than 1.1 mg/dL or a doubling of the serum creatinine concentration in the absence of other renal disease); pulmonary oedema or new-onset cerebral or visual disturbances

The authors analysed data from a cohort of 193 women (n=172 with labour and n=21 with planned Caesarean section). The prevalence of the outcome was 15.5%. Women exposed to labour did not have a higher rate compared with planned Caesarean sections (16.3% vs 9.5%, P=0.4). Adjusting for confounders, women delivered by Caesarean section after prolonged labour had a 10-fold higher adverse outcome risk compared with women with a planned Caesarean section (adjusted odds ratio (aOR) 9.7 (1.2 to 78.6), P=0.03) or with a vaginal delivery <24 h (aOR 9.7 (1.4 to 67.4), P=0.02). In conclusion, prolonged labour and Caesarean section in labour were both associated with an increase in the primary outcome.


Ethnicity plays a major role in the risk profile for pre-eclampsia. Ray et al examined preterm pre-eclampsia in relation to country of birth.5 Using a population-based study involving the province of Ontario, Canada which has universal access to obstetric care, the authors examined data from 881,700 singleton live births among Canadian-born mothers and 305,547 births among immigrant mothers. Adjusted risk ratios (aRRs) were adjusted for maternal age, parity and income quintile.

The rate of preterm pre-eclampsia was 4.0 per 1000 among Canadian-born mothers. The aRR of preterm pre-eclampsia at 24 to 36 weeks was significantly higher for immigrant women from Nigeria (1.79, 95% confidence interval (CI) 1.12 to 2.84), the Philippines (1.54, 95% CI 1.30 to 1.86), Colombia (1.68, 95% CI 1.04 to 2.73), Jamaica (2.06, 95% CI 1.66 to 2.57) and Ghana (2.12, 95% CI 1.40 to 3.21). The aRRs generally followed a similar pattern for secondary outcomes. Specifically, women from Ghana were at highest risk of extreme preterm pre-eclampsia between 24-31 weeks’ gestation (4.55, 95% CI 2.57 to 8.06), and women from Jamaica at the highest risk of preterm pre-eclampsia 24-36 weeks’ gestation excluding preterm spontaneous labor with preterm delivery or premature rupture of membranes (1.89, 95% CI 1.43 to 2.50).


  1. Magnus MC, Haberg SE, Magnus P, et al. Pre-eclampsia and childhood asthma. Eur Respir J. 2016;48(6):1622-1630.
  2. Broekhuijsen K, van Baaren GJ, van Pampus MG, et al. Immediate delivery versus expectant monitoring for hypertensive disorders of pregnancy between 34 and 37 weeks of gestation (HYPITAT-II): an open-label, randomised controlled trial. Lancet. 2015;385(9986):2492-2501.
  3. Levine LD, Elovitz MA, Limaye M, Sammel MD, Srinivas SK. Induction, labor length and mode of delivery: the impact on preeclampsia-related adverse maternal outcomes. J Perinatol. 2016;36(9):713-717.
  4. American College of O, Gynecologists, Task Force on Hypertension in P. Hypertension in pregnancy. Report of the American College of Obstetricians and Gynecologists’ Task Force on Hypertension in Pregnancy. Obstetrics and gynecology. 2013;122(5):1122-1131.
  5. Ray JG, Wanigaratne S, Park AL, Bartsch E, Dzakpasu S, Urquia ML. Preterm preeclampsia in relation to country of birth. J Perinatol. 2016;36(9):718-722.