Clinical Practice Guidelines Antenatal Care — Module II

6.7Risk of pre-eclampsia

Background

In pre-eclampsia, hypertension is accompanied by one or more of the following features (Lowe et al 2008):

impaired kidney or liver function;

haematological involvement;

neurological symptoms (headache, visual disturbances, stroke, convulsions);

pulmonary oedema;

fetal growth restriction; and/or

placental abruption.

Pre-eclampsia is a progressive disorder that worsens if pregnancy continues (Lowe et al 2008). Birth of the baby is the definitive treatment and is followed by resolution, generally over a few days but sometimes much longer (Lowe et al 2008). Decisions about management (eg induction/caesarean section or continuation of the pregnancy) are based on maternal and fetal factors (eg gestational age) (Lowe et al 2008). Early onset pre-eclampsia (<37 weeks) is associated with poorer outcomes (Lowe et al 2008).

Prevalence of pre-eclampsia

In 2009–10, a total of 7,738 women in Australia were hospitalised for pre-eclampsia (AIHW Hospitals Data); around 2.6% of births. There are no data on the difference in rates of pre-eclampsia between Aboriginal and Torres Strait Islander and non-Indigenous women.

In 2010, hypertension or pre-eclampsia were the reasons for 3.1–12.8% of labour inductions in New South Wales, Queensland, South Australia, Tasmania and the Northern Territory and 2.3–4.8% of caesarean sections in Queensland, South Australia, Tasmania and the Northern Territory. Data collection methods varied and, for other states and territories, were unavailable or unpublished (Li et al 2012).

Of the five maternal deaths due to hypertensive disease in Australia in 2003–05 (Sullivan et al 2008), two were attributed to eclampsia. One woman had pre-eclampsia in her previous pregnancy but no evidence of pre-eclampsia in the pregnancy preceding her death.

A decline in the incidence of pre-eclampsia and associated maternal mortality in high income countries occurred between 1940 and 1970 with widespread uptake of antenatal care and increased access to hospital care for timely induction of labour or caesarean section for women with severe pre-eclampsia (Goldenberg et al 2011), and more recently, with the introduction of treatment with magnesium sulphate (Duley et al 2010).

Risks associated with pre-eclampsia

Women with complicated pre-eclampsia are more likely to have a caesarean section, stillbirth or neonatal death (Bhattacharya & Campbell 2005).

Neonatal complications associated with pre-eclampsia in a large cross-sectional study (n=647,392)(Schneider 2011) were small for gestational age, acute respiratory distress syndrome, postpartum neonatal hypoglycaemia and low Apgar scores.

Assessing risk of pre-eclampsia

Summary of the evidence

Identifying women with risk factors for pre-eclampsia

Factors associated with a high risk of pre-eclampsia include (NICE 2008):

a history of pre-eclampsia (Mendilcioglu et al 2004; Lain et al 2005; Ananth et al 2007; Poon et al 2010; Sibai et al 2011);

pre-existing hypertension (Lowe et al 2008; Poon et al 2010);

pre-existing kidney disease;

pre-existing or gestational diabetes (Bryson et al 2003; Yogev et al 2004; Ostlund et al 2006; HAPO 2010);

autoimmune disease such as systemic lupus erythematosis or antiphospholipid syndrome; and

raised blood pressure at the first antenatal visit.

Factors associated with a moderate risk of pre-eclampsia include (NICE 2008):

first or multiple pregnancy (eg twins or triplets);

age >40 years;

more than 10 years since the last pregnancy;

BMI greater than 35 kg/m² at first visit (O’Brien et al 2003; Bodnar et al 2005; Erez-Weiss et al 2005; Fredrick et al 2006; Cnossen et al 2007; Getahun et al 2007; Becker et al 2008; Driul et al 2008; Aliyu et al 2010; Briese et al 2010; Mbah et al 2010; Anderson et al 2012); and

family history of pre-eclampsia (Poon et al 2010) or hypertensive disease (Qiu et al 2004; Roes et al 2005; Bezerra et al 2010; Jelin et al 2010).

Risk of pre-eclampsia may also be associated with use of ovulation induction medication and African or Indian subcontinent origin (Poon et al 2010) and Factor V Leiden (Kosmas et al 2003; Dudding et al 2008).

While there may be an association between active maternal periodontal disease during pregnancy and pre-eclampsia (Boggess et al 2003), treatment of periodontal disease does not appear to affect the level of risk (Newnham et al 2009) (see Section 10.5 of Module I).

Routinely measure blood pressure to identify new onset hypertension.

Preventive measures

Recommendation 12 Grade A

Advise women at high risk of developing pre-eclampsia that calcium supplementation is beneficial if dietary intake is low.

Practice point p

If a woman has a low dietary calcium intake, advise her to increase her intake of calcium-rich foods.

low-dose aspirin has moderate benefits when used for prevention of pre-eclampsia (relative risk [RR]: 0.78; 95% CI: 0.67–0.90) (Duley et al 2007);

there was a reduction in risk among women at risk (eg with previous pre-eclampsia) (RR: 0.79; 95% CI: 0.65–0.97) but not those with low risk (Trivedi 2011);

the relative risk of developing pre-eclampsia was 0.90 (95% CI 0.84–0.97), of giving birth before 34 weeks was 0.90 (95% CI 0.83–0.98), and of having a pregnancy with a serious adverse outcome was 0.90 (95% CI 0.85–0.96) (Askie et al 2007); and

the effect was only significant for preterm pre-eclampsia (RR 0.11, 95% CI 0.04–0.33) (Roberge et al 2012).

Recommendation 13 Grade B

Advise women at moderate–high risk of pre-eclampsia that low-dose aspirin from early pregnancy (preferably before 20 weeks) may be of benefit in its prevention.

Vitamins: There is insufficient evidence that the risk of pre-eclampsia is reduced by supplementing vitamin B₂ (Neugebauer et al 2006) or vitamins C and E (Beazley et al 2005; Rumbold & Crowther 2005; Poston et al 2006; Rumbold et al 2006; Polyzos et al 2007; Spinnato et al 2007; Klemmensen et al 2009; Rahimini et al 2009; Basaran et al 2010; Xu et al 2010; Conde-Agudelo et al 2011; Rossi & Mullin 2011; Salles et al 2012). Some studies have found associations between supplementation with vitamins C and E in women at risk of pre-eclampsia and adverse effects, including low birth weight, hypertension and premature rupture of the membranes (Poston et al 2006; Rahimini et al 2009; Xu et al 2010; Conde-Agudelo et al 2011).

Recommendation 14 Grade B

Advise women that vitamins are not of benefit in preventing pre-eclampsia.

Physical activity: A systematic review found a trend towards a protective effect from leisure time or recreational physical activity during pregnancy in case-control studies (OR: 0.77; 95%CI: 0.64–0.91) but no significant effect in prospective cohort studies (Kasawara 2012). Physical activity during pregnancy has general health benefits (see Section 5.4).

Salt intake: Reducing salt intake does not reduce the risk of pre-eclampsia (Duley et al 2005). However, avoiding foods with added salt has other health benefits (NHMRC 2013).

Identifying women with clinical signs of pre-eclampsia

Measurement of blood pressure and testing for proteinuria is discussed in Module I of the Guidelines (see Sections 7.3 and 7.4).

Recommendation 15 Grade C

Offer testing for proteinuria if a woman has risk factors for, or clinical indications of, pre-eclampsia; in particular raised blood pressure.

Where possible, women with clinical signs of pre-eclampsia (hypertension, proteinuria, growth restriction) should be referred for specialist assessment and management.

Predicting pre-eclampsia

Due to the progressive nature of pre-eclampsia and a lack of therapies effective in altering its progression (Lowe et al 2008), these tests are unlikely to change interventions or outcomes (NICE 2008).

Section 6.8 includes resources on the management of hypertensive disorders in pregnancy.

Discussing risk of pre-eclampsia

Women should be given information about the urgency of seeking advice from a health professional if they experience:

• headache;

• visual disturbance, such as blurring or flashing before the eyes;

• epigastric pain (just below the ribs);

• vomiting; and/or

• rapid swelling of the face, hands or feet.

Practice summary: pre-eclampsia