Pregnancy blood pressure



Blood pressure complications in pregnancy  

Swelling legs, varicose veins in pregnancy  

 Possible complications of pregnancy are that the mother develops high blood pressure (gestational hypertension) or diabetes (gestational diabetes).

In the early stages of pregnancy a woman’s blood pressure usually falls. It then slowly rises and by the time the baby is due it is back to pre-pregnancy levels. If the blood pressure rises too much, measured around 20 weeks of pregnancy, she has gestational hypertension. Pre-eclampsia is a separate serious condition where blood pressure is high and protein is found in the urine. The liver, kidneys, brain and placenta are affected and the blood clots more readily so that possible complications for the mother include seizures (eclampsia), stroke, liver or kidney failure. It can lead to death of the mother.

Women with diabetes, renal disease, thrombophilia, autoimmune disease, previous severe or early onset pre-eclampsia, or carrying more than one infant (multiple pregnancy) increases the chances of developing pre-eclampsia. Obesity and age (either a teenager or over the age of 35 years) are also risk factors.

The baby may be small for the date after conception, be born with a low birthweight and have a low Apgar score at birth or need to be admitted to a special care neonatal unit. The Apgar score rates the baby’s color, heart rate, response to stimulation of the sole of the foot, muscle tone, and respiration. Giving birth before 37 weeks of pregnancy (preterm) is often caused by high blood pressure and is the leading cause of newborn deaths, particularly in low-income countries.

We present some of the evidence from Cochrane systematic reviews about complementary and alternative treatments related to pregnancy. This evidence comes from carefully researched reviews of information about clinical trials done to evaluate medical treatments. Studies are only included in these reviews if they meet pre-defined criteria.


High blood pressure is common during pregnancy in that around 10% of women have raised blood pressure at some point before delivery. Gestational hypertension, a rise in blood pressure during the second half of pregnancy is called gestational hypertension.

Pre-eclampsia is a serious complication of pregnancy identified by increased blood pressure and protein in the urine in the second half of pregnancy. If the blood vessels in the placenta are constricted, it can interfere with nutrients and oxygen passing to the baby so that the baby's growth is restricted and it may be born early (preterm). Pre-eclampsia can negatively affect the mother’s kidneys, liver, brain, and clotting system.

What is known

Garlic has been reported to lower blood pressure, reduce clumping of platelets (aggregation), and reduce oxidative stress. It may, therefore, be able to reduce the risk of pre-eclampsia and complications. The traditional medicinal uses of garlic include prevention of infection and treatment of colds, influenza, bronchitis, whooping cough, gastroenteritis, dysentery and skin problems.
Garlic (Allium sativum) is part of the Allium, or onion, family. Garlic's main active ingredient is thought to be allicin, a strong smelling sulphide. Allicin is formed from garlic's main sulphur compound, alliin, by the action of the enzyme alliinase, for example when raw garlic cloves are crushed or chewed.  

What the synthesised research says

Taking garlic did not clearly protect the women from developing gestational hypertension (relative risk (RR) 0.50, range 0.25 to 1.00) or pre-eclampsia. The number of women requiring a caesarean section also did not appear to be affected. This was from one trial involving 100 pregnant women.

How it was tested

The review of trials found just one controlled study from Iran in which 100 women were randomised to receive dried garlic tablets or non-active placebo tablets. The women were 28 to 32 weeks pregnant with their first baby who were women at moderate risk of pre-eclampsia, as determined by a blood pressure test that involves changing body position by rolling over.

There was no clear difference between the garlic and control groups in the risk of developing gestational hypertension (relative risk (RR) 0.50, range 0.25 to 1.00) or pre-eclampsia (RR 0.78, range 0.31 to 1.93).

The number of caesarean sections was unchanged (RR 1.35, range 0.93 to 1.95), and there were no perinatal deaths in the study.

In this small study, garlic was given in tablet form, and the tablets were claimed to be 'odour controlled'. Nevertheless, one third of women taking the active treatment reported odours, compared to only 4% on placebo. Such odours may be acceptable in communities with a high dietary intake of garlic, but may be unacceptable where garlic intake is lower. Moreover, pregnant women may be particularly sensitive to odour, which may influence compliance with the intervention in communities with low dietary intake.

Women allocated garlic were more likely to report odour than those allocated placebo but there was no clear difference in other reported side-effects. About one-third of the women in the active group reported odour. From other reports, garlic is generally well tolerated with minor gastrointestinal disturbances of nausea and diarrhoea and allergic reactions. Several reports suggest that there may be an increased tendency to bleed with concurrent use of anticoagulants (AHRQ 2000) but and more serious side-effects have not been reported.

The one included study was of uncertain methodological quality as there was no information on the exact methods used for allocation generation or concealment; caregivers and outcome assessors were not blinded to the treatment given.

There are no recommendations for standard intake of garlic. In early studies that used raw garlic, the dosage required to obtain health benefits was relatively high, ranging from 7 to 28 cloves per day. In more recent studies that have used commercial preparations of garlic, the daily dosage has ranged from 600 mg to 1000 mg.

A problem with research into the effects of garlic is assessing the bioavailability of active constituents after ingestion. There are many forms of garlic including fresh cloves, powdered garlic, garlic capsules and there may be differences between these preparations. It has been recommended that commercial garlic preparations should be systematically tested for their ability to release allicin.


Meher S, Duley L. Garlic for preventing pre-eclampsia and its complications. Cochrane Database of Systematic Reviews 2006, Issue 3. Art. No.: CD006065. DOI: 10.1002/14651858.CD006065.Agency for Healthcare Research and Quality. Garlic: effects on cardiovascular risks and disease, protective effects against cancer, and clinical adverse effects. Summary, Evidence Report/Technology Assessment: Number 20. AHRQ Publication No. 01-E022, October 2000. Agency for Healthcare Research and Quality, Rockville, MD. (accessed April 2005).


Studies of fish-eating communities provide evidence that high intakes of marine foods during pregnancy are associated with longer pregnancies (gestations), higher infant birthweights and a low incidence of pre-eclampsia. It is suggested that it is the fatty acids of marine foods that bring this about.

Observation studies show a strong association between the dietary dose of the polyunsaturated fatty acid docosahexaenoic acid (DHA) in pregnancy and the prevalence of depressive symptoms in the postnatal period, sleeping patterns of the newborn infant, and neural development (altered attention and motor development). Eicosapentaenoic acid (EPA) is another of these fatty acids that are used in the body to produce prostaglandins that modulate inflammatory, vascular effects and uterine smooth muscle.

What the synthesised research says

The risk of developing pre-eclampsia was not clearly different when women took marine oil supplements.

Women on the supplements had a two to three day longer pregnancies than those on a non-active placebo or no treatment (3 trials, 1621 women), possibly slightly more for women with high risk pregnancies. Correspondingly, the newborn infants were slightly heavier when the mother was taking marine oil supplements (WMD 47 g, range 1 g to 93 g; 3 trials, 2440 women).

There were no overall differences in the relative risk of preterm birth (before 37 completed weeks) between marine oil and control treatment but women allocated marine oil did have a lower risk of giving birth before 34 completed weeks' gestation (relative risk RR 0.69, range 0.49 to 0.99; 2 trials, 860 women).

The proportion of babies who had a low birthweight or were small for their gestational age were no different with and without marine oils.

How it was tested

These conclusions are drawn from six controlled trials, involving 2783 women. The women were randomly assigned to receive marine oil (fish or algal oils) or other oils, such as evening primrose or borage oil, taken by mouth, compared with placebo or no marine oil treatment, to prevent pre-eclampsia or growth restrictions of the baby.

Most trials commenced supplementation after 16 weeks' pregnancy (gestation). Three of the six trials included women with high-risk pregnancies.

The most commonly used dose was 2.7 g of EPA and DHA per day (2242 women) (ranging from 133 mg/day to 3 g/day of marine oils (EPA and DHA)).

There were no clear differences in the relative risk (RR) of high blood pressure (5 trials, 1831 women) or the incidence of pre-eclampsia (4 trials, 1683 women) between marine oil treated and control groups. This was regardless of the timing of supplementation, whether women were exclusively treated with marine oil, or whether women had high risk pregnancies for pre-eclampsia, preterm birth or growth restriction.

Side effects and general cautions

An increased length of pregnancy may not be so desirable if it also prolongs gestation beyond term. The majority of women taking marine oil could guess their group allocation, largely because of belching and an unpleasant taste associated with taking the fish oil supplements. Nausea, vomiting, stomach pain, diarrhoea and constipation were similar in the two groups and there were no bleeding problems evident with marine oils.
Three trials were rated as high quality, including the largest trial with 1477 women.


Makrides M, Duley L, Olsen SF. Marine oil, and other prostaglandin precursor, supplementation for pregnancy uncomplicated by pre-eclampsia or intrauterine growth restriction. Cochrane Database of Systematic Reviews 2006, Issue 3. Art. No.: CD003402. DOI: 10.1002/14651858.CD003402.pub2.


Pre-eclampsia is characterised by high blood pressure and protein in the urine, but can also affect the kidneys, liver and blood-clotting systems. Rare complications include convulsions and it can cause maternal death.

Giving birth before 37 weeks of pregnancy (preterm birth) is often caused by high blood pressure and is the leading cause of newborn deaths, particularly in low-income countries. The baby may also be small with poor growth because of reduced supply of nutrients across the mother’s placenta. It is at high risk of becoming ill, especially with respiratory and neurological problems.

Observations that raised blood pressure (hypertensive) problems during pregnancy are low in communities that have a high calcium intake has led to the suggestion that an increase in calcium intake during pregnancy might reduce the incidence of high blood pressure and pre-eclampsia. This is particularly for women with low calcium intake (around less than 900 mg per day).

Calcium supplements are relatively cheap, widely available and are likely to be safe for woman and their children.

What the synthesised research says

Supplementation with calcium from about 20 weeks of pregnancy (in most trials) almost halved the risk of pre-eclampsia and reduced the rare occurrence of death and serious illness, compared with a non-active supplement (placebo). The effects were smaller in the larger trials; there were no other clear benefits, or harms.

How it was tested

The review authors made a thorough search of the medical literature and found twelve well-designed controlled studies from a range of countries including Argentina, USA, Australia and an international multicentre trial. Most of the 15,206 women recruited to the trials were carrying their first child, assessed as at low risk of developing high blood pressure (14,619 women) and had a low dietary intake of calcium (10,154 women). They were given either a supplement of calcium, generally 1.5 g to 2 g per day, or a non-active placebo, starting from 34 weeks of pregnancy at the latest.

Taking calcium supplements from about 20 weeks pregnancy almost halved the risk of high blood pressure (11 trials, 14,946 women: relative risk (RR) 0.70, 95% confidence interval (CI) 0.57 to 0.86) and pre-eclampsia (12 trials, 15,206 women: RR 0.48, 95% CI 0.33 to 0.69). This effect was greatest for high-risk women and those with low dietary calcium intake. The risk of women developing high blood pressure was also reduced. The risks of preterm birth, stillbirth or death before discharge from hospital were not clearly reduced in these trials.

The risk of preterm birth was not affected overall (10 trials, 14,751 women) but it was halved for women at high risk of developing pre-eclampsia (4 trials, 568 women: RR 0.45, range 0.24 to 0.83). There was no clear overall effect on the risk of having a baby with birthweight less than 2500 g (8 trials, 14,359 women) or being born small-for-gestational age (3 trials 13,091 women).

Stillbirths and deaths of infants before discharge from hospital were similar (10 trials 15,141 babies) and a very small (5%) reduction in the risk of caesarian section is possible (7 trials, 14,710 women). The composite outcome maternal death or serious illness was reduced by 20% (95% CI 35% to 3%) for women allocated calcium supplementation (4 trials, 9732 women).

Side effects and general cautions

The trialists did not report any side-effects of calcium supplementation. All were well designed, double-blind, placebo-controlled trials. Maternal deaths were reported in only one trial. Starting supplementation in the middle trimester of pregnancy, as was done in these trials, may be too late to be fully effective. Almost all the women in these trials were at low risk of developing pregnancy complications but had a low calcium diet.

There is little information about the long-term follow up of the infants, with the exception of a reduction in childhood systolic high blood pressure in the one study to measure this. Women with diagnosed hypertensive disorders of pregnancy were excluded from the trials.


Hofmeyr GJ, Atallah AN, Duley L. Calcium supplementation during pregnancy for preventing hypertensive disorders and related problems.Cochrane Database of Systematic Reviews 2006, Issue 3. Art. No.: CD001059. DOI: 10.1002/14651858.CD001059.pub2.


Vitamin E includes eight fat soluble and plant-derived compounds, four are referred to as tocopherols and four are known as tocotrienols (alpha, beta, gamma, delta). Natural source alpha-tocopherol is the most biologically active form of vitamin E and is found in wheatgerm oil and other vegetable oils, nuts, some cereals and some leafy green vegetables. Synthetic forms of vitamin E are also available and are commonly used in vitamin preparations. Vitamin E is an antioxidant.

What is known

In pregnant women minimal vitamin E is lost to the fetus. This means that the recommended dietary intake (RDI) of vitamin E is generally unchanged during pregnancy. Healthy adults rarely have a deficiency.

Pre-term infants and infants with low birthweights or problems with absorbing the fat in their feeds may have deficiencies. Symptoms include anaemia, high levels of the breakdown product of haemoglobin (bilirubin) and peripheral neuropathy. Vitamin E deficiency is worse with high iron levels and a high dietary intake of polyunsaturated fatty acids, which is of particular relevance for preterm infants fed formula containing high levels of iron and these fatty acids. Vitamin E supplementation may help reduce the risk of pregnancy complications such as pre-eclampsia.

What the synthesised research says

The evidence that pregnant women given vitamin E in combination with other supplements are less likely to develop pre-eclampsia is unclear. This conclusion is based on three trials involving 510 women.

No benefit was found on the risk of stillbirths, neonatal death, perinatal deaths, preterm births, or clear effects on intrauterine growth restriction or birthweights. These were looked at in one or two trials, involving 40 to 383 women.

Vitamin E was given with vitamin C and additional supplements or drugs.  

How it was tested

The researchers made a comprehensive search of the medical literature and found four trials involving 566 pregnant women for inclusion in the review. Three trials looked at vitamin E supplementation compared with non-active placebo for the prevention of pre-eclampsia, one for the prevention of serious complications for mothers and for preterm births when women had established early onset pre-eclampsia.

Side effects and general cautions

Only one of the trials reported on side effects. This trial involved 56 women and reported potential side-effects of vitamin E including acne, transient weakness and skin rash.

The total number of women involved in the trials was small and two trials were not well conducted with only abstracts published.

All of the women involved were either at high risk of pre-eclampsia or had established severe early onset pre-eclampsia. This means that no information is available for healthy pregnant women on using vitamin E supplementation.

Vitamin E was not given alone but with vitamin C and additional supplements or drugs. The researchers excluded trials using a multivitamin supplement that contained vitamin E.


Rumbold A, Crowther CA. Vitamin E supplementation in pregnancy. The Cochrane Database of Systematic Reviews 2005, Issue 2. Art. No.: CD004069.pub2. DOI: 10.1002/14651858.CD004069.pub2.


Pregnancy seems to increase the risk of varicose veins. These can be painful and can cause cramps at night; numb, tingling or heavy aching legs. The veins carry blood back to the heart and to assist this process the veins have a series of valves which close between heartbeats to prevent the blood flowing backwards. When a valve weakens, particularly in the legs, the blood does not flow so that the vein enlarges and can be seen near the surface of the skin.

The feet and ankles may also swell with the slowing down of the blood circulation. Symptoms tend to worsen after long periods of standing and with each successive pregnancy.

A similar process in the rectum causes haemorrhoids (piles).

What is known

For most women who develop varicose veins during pregnancy, the symptoms appear during the first three months of pregnancy (first trimester), often within two to three weeks of becoming pregnant. For the majority of women, leg swelling reduces soon after giving birth and varicose veins subside on their own within three or four months of the baby's birth.
Non-drug or surgical therapies are rest and leg elevation, wearing compression stockings during the day, immersion in water, reflexology, exercise and physiotherapy.

When resting for long periods, women are advised to rest on their left side because the main abdominal vein (inferior vena cava) is on the right. Left-sided rest relieves the vein of the weight of the uterus, thus decreasing pressure on the veins in the legs and feet). Gentle flexion of the foot to stretch the calf muscles is also advised.
Reflexology involves the concept that all body organs and glands have corresponding reflex points in the feet, hands and ears. It has the potential to provide pain relief and symptom relief and induce relaxation without harmful side-effects.

What the synthesised research says

Wearing compression stockings for 30 minutes does not seem to help prevent the legs swelling with a 10-minute walk, compared with a 15-minute rest on the left side (one trial, 35 women).
Reflexology appears to help improve symptoms for women with leg oedema compared with resting, based on one small study involving 55 women.

How it was tested

Three randomized controlled trials, involving 159 women, were included in the review, one used the part synthetic drug rutoside for varicose veins. The other trials randomized the women to wear compression stockings or have reflexology compared with resting for relieving leg swelling.

Reflexology clearly reduced the symptoms associated with oedema (reduction in symptoms: RR 9.09, 95% CI 1.41 to 58.54). The women did not clearly prefer reflexology. This study compared two different reflexology techniques (relaxing and lymphatic) with no clear differences in effectiveness or woman's satisfaction and acceptance of the two techniques.

Side effects and general cautions

The possibility of adverse effects remains; the safety of both pharmacological and non-pharmacological interventions of all the interventions in this review cannot be verified from the available data.
The included trials were small, therefore, the evidence available from these trials is insufficient to draw reliable conclusions for clinical practice.


Bamigboye AA, Smyth R. Interventions for varicose veins and leg oedema in pregnancy. Cochrane Database of Systematic Reviews 2007, Issue 1. Art. No.: CD001066. DOI: 10.1002/14651858.CD001066.pub2.