Existing high blood pressure in patients is a major risk factor threatening the success of a pregnancy, making adequate surveillance essential, a new UK study suggests.
Chronic hypertension is associated with a high likelihood of adverse pregnancy outcomes including preterm delivery, low birth weight and neonatal death, according to a research paper published by the BMJ this week.
The long-term condition affects between 1-5% of pregnancies and that figure may be growing because of rising rates of obesity, which may be contributory factors.
A recent US study indicated there was an increase in the prevalence of chronic hypertension from 1995-1996 to 2007-2008, after adjustment for maternal age.
In the new study, King’s College London researchers set out to investigate the strength of evidence linking chronic hypertension with poor pregnancy outcomes – combining data from 55 studies conducted in 25 countries.
They looked at a wide range of outcomes – preterm delivery (delivery before 37 weeks’ gestation), low birth weight (below 2,500g), perinatal death (foetal death after 20 weeks’ gestation including stillbirth and neonatal death up to one month), and admission to neonatal intensive care or special care baby units.
The researchers found women with chronic hypertension faced a relative risk of pre-eclampsia that was on average almost eight times higher than women who did not have hypertension.
All adverse neonatal outcomes were found to be at least twice as likely to occur in the women with hypertension compared to the general population.
“Chronic hypertension is associated with a high incidence of adverse pregnancy outcomes compared with a general population,” the researchers said.
They stated that antenatal surveillance for women with chronic hypertension is of extreme importance and suggest such women should receive pre-pregnancy counselling to optimise their health prior to pregnancy.
“These are more complex pregnancies requiring more time and resources”
The study authors also called for strategies to help predict which women are at greatest risk of hypertension.
Mervi Jokinen, practice and standards development advisor at the Royal College of Midwives, said: “This is an important issue highlighting the need for good antenatal care.
“Midwives are well aware of the risks of existing hypertension in pregnancy and the need for individualised care for each woman, supporting and advising women as well as providing clinical care.
“Maternity services have to ensure midwives are able to work closely with different healthcare professionals in providing care for these women, therefore improving communication and pregnancy outcomes,” she said.
“These are more complex pregnancies requiring more time and resources and most importantly, enough midwives with enough time to support women,” she added.
- Read the full study paper in BMJ