Dr Fergus McCarthy takes a look at the news this month…

Over recent years, placental growth factor has featured prominently as a marker both for longer term prediction of pre-eclampsia in the first trimester but also in predicting the need for delivery in the third trimester. As interest in this marker has increased, so too have the number of PlGF based assays.  McCarthy et al compared the performance of three PlGF-based kits in the prediction of time to delivery within 14 days in women with suspected preterm pre-eclampsia prior to 35 weeks’ gestation.1

The authors conducted a retrospective analysis of samples collected from three prospective pregnancy cohort studies. Participants were pregnant women with suspected preterm pre-eclampsia recruited in tertiary maternity units in the UK and Ireland. Samples were analysed simultaneously according to manufacturer’s directions using three platforms; DELFIA Xpress PlGF 1-2-3 test, Triage PlGF test and Elecsys immunoassay sFlt-1/PlGF ratio. Areas under the receiver operating curve (AUROC) were compared. The main outcome measure was the detection of a difference of 0.05 in AUROC between tests for time to delivery within 14 days of testing.

Plasma samples from 396 women and serum samples from 244 women were assayed. No significant difference was observed in prediction of delivery within 14 days secondary to suspected pre-eclampsia prior to 35 weeks’ gestation in AUROC (p= 0.795), sensitivities (p= 0.249), positive predictive values (p= 0.765) or negative predictive values (p= 0.920). The authors concluded that tests compared similarly in their prediction of the need for delivery within 14 days. The negative predictive values supported the role of PlGF based tests as a ‘rule-out’ test for pre-eclampsia.  

Studies suggest that the use of folic acid may lower the risk of hypertensive disorders in pregnant women. De Ocampo et al investigated the use of folic acid supplements and the risk of gestational hypertension and pre-eclampsia.2 The authors assessed the effects of timing and duration of folic acid-containing supplement use on the risk for gestational hypertension and pre-eclampsia.

Exposures and outcomes data were obtained through interviews and review of participant’s medical records from the MotherToBaby cohort studies across the United States and Canada. Demographics, medical history, lifestyle factors, substance use, and fetal sex were assessed as potential confounders. Unadjusted and adjusted risks for gestational hypertension and pre-eclampsia were examined using odds ratios and 95% confidence intervals.

3247 women were included in the study. Compared to non-supplement use, early and late supplement use were not significantly associated with the development of gestational hypertension or pre-eclampsia. The odds of developing gestational hypertension and pre-eclampsia were significantly reduced as the duration of folic acid-containing supplement use increased.

The authors concluded that the use of folic acid-containing supplements may mitigate the risk for gestational hypertension and pre-eclampsia.

The duration of treatment of women with pre-eclampsia with magnesium sulphate to confer protection against eclampsia remains unclear.  Vigil-De Gracia conducted a randomized clinical trial examining the use of magnesium sulfate for 6 vs 24 hours post delivery in patients who received magnesium sulfate for less than 8 hours before birth.3

They conducted a randomized, multi-center, open study between November 2013 and October 2016 in three teaching maternity hospitals in Panama. Pregnant women diagnosed with severe pre-eclampsia or pre-eclampsia with severe features at more than 20 weeks gestation were invited to participate. They were randomized to the following groups in a 1:1 ratio: A- continue Mg for 24 hours after birth (control group); and B- receive Mg for 6 hours after birth (experimental group). The primary endpoint and variable was seizure (eclampsia) in the first 72 hours postpartum.

During the study period, 284 patients agreed to participate in the study; 143 were randomized to receive Mg for 24 hours postpartum and 141 to receive Mg for 6 h postpartum. There were no significant differences in the baseline characteristics of the two groups studied. No cases of eclampsia occurred in the entire population, therefore, there was no significant difference in the primary variable. Two secondary variables showed a significant difference: time to onset of ambulation, which was 14 hours shorter (p = 0.0001) in the group that received 6 hours of postpartum Mg, and time to initiation of breastfeeding, which was 11 hours earlier (p = 0.0001) in the group that received 6 hours of postpartum Mg. There were not significant differences between the groups with respect to total complications or any particular complication. There were no cases of maternal death.

Maintaining Mg for 6 hours postpartum is equally effective in preventing eclampsia as receiving Mg for 24 hours postpartum in patients with severe pre-eclampsia who receive less than 8 hours of Mg treatment before birth. The onset of maternal ambulation and initiation of breastfeeding are faster in patients who only receive Mg for 6 hours postpartum.

References

  1. McCarthy FP, Gill C, Seed PT, Bramham K, Chappell LC, Shennan AH. Performance of commercially available placental growth factor tests in women with suspected preterm pre-eclampsia; the COMPARE study. Ultrasound in obstetrics & gynecology: the official journal of the International Society of Ultrasound in Obstetrics and Gynecology. 2018.
  2. De Ocampo MPG, Araneta MRG, Macera CA, Alcaraz JE, Moore TR, Chambers CD. Folic acid supplement use and the risk of gestational hypertension and preeclampsia. Women Birth. 2018;31(2):e77-e83.
  3. Vigil-De Gracia P, Ramirez R, Duran Y, Quintero A. Magnesium sulfate for 6 vs 24 hours post delivery in patients who received magnesium sulfate for less than 8 hours before birth: a randomized clinical trial. BMC pregnancy and childbirth. 2017;17(1):241.