Blood pressure begins to decrease progressively after the first weeks of pregnancy, stabilizing at around 75 mmHg (diastolic pressure) throughout the rest of the first and second trimester of gestation. In the last two to three months before birth, however, blood pressure levels return to pregravidical levels, ie around 85 mmHg for diastolic. We talked about minimum pressure since the drop is mainly due to diastolic blood pressure (PAD) and - beyond the starting values - in the first and second trimester it can be quantified in about 7-10 mmHg.
A very important organ for a successful pregnancy is the placenta, which represents the communication interface between mother and fetus. At this level, in fact, thanks to an articulated system of blood vessels and microvases, the exchange of nutrients, waste substances and gas takes place between the blood of the two organisms, without there being direct contact between the two fluids. In order for all these exchanges to take place, it is necessary that a considerable amount of maternal blood reach the placental level, with reduced speed and equally low pressure.
When the formation of the placenta is not complete or is defective, the final product does not work as it should: its resistances, not sufficiently low, induce an increase in pressure upstream, ie in the maternal organism. Unfortunately, during pregnancy high blood pressure is dangerous for maternal and fetal health, so that in extreme cases it can endanger the very life of both organisms. This form of hypertension, which affects about 6-8% of pregnant women, is known as gestational or pregnancy-induced hypertension. It is often associated with urinary protein loss (proteinuria) and in this case is called gestosis or preeclampsia. Precisely for this reason, arterial pressure values are carefully checked at each obstetric control, during which urinalysis is always provided.
Hypertension in pregnancy
Hypertension in pregnancy is defined as the presence of one or more of the criteria illustrated below, found in at least two measurements taken at least 4 hours apart:
- - Detection of blood pressure ≥ 140/90 mmHg
- Increased systolic blood pressure (maximum), compared to preconception, ≥ 25 mmHg (WHO) or ≥ 30 mmHg (ACOG)
- Increased diastolic blood pressure (minimum), compared to preconception, ≥ 15 mmHg
ACOG = American College of Obstetrics and Gynecology; WHO = World Health Organization.
Preeclampsia
Preeclampsia is characterized by the appearance of hypertension (as defined above), proteinuria (> 0.3 g / 24 hours) and / or edema (feet, face, hands) after the twentieth week of gestation, in a woman previously normotensive. Preeclampsia is a wake-up call for an even more severe form of gestational hypertension, eclampsia, characterized by the appearance of seizures.
Predisposing factors for preeclampsia
Nulliparity (risk> 6-8 times)
Twin pregnancy (risk> 5 times)
Diabetes
Hydatidiform and fetal hydrops (risk> 10 times)
Preeclampsia in previous pregnancies
Chronic hypertension
Extreme ages
Preeclampsia symptoms
The clinical manifestations of hypertensive disorders may appear at any time during pregnancy, starting from the second trimester up to several days after delivery. They include:
hypertension, tachycardia, changes in respiratory rate
Headache, dizziness, buzzing, drowsiness, fever, hyperreflexia, diplopia, blurred vision, sudden blindness.
Nausea, vomiting, epigastric pain, hepatomegaly, hematemesis.
Proteinuria, edema, oliguria or anuria, hematuria, hemoglobinuria.
Eclampsia
Eclampsia is defined as the presence of generalized convulsions, due to encephalopathy associated with preeclampsia and not attributable to other causes. it is a rare but serious complication (1: 2000 parts in developed countries) of gravidic hypertension.As the name suggests, gravidic hypertension disappears at the end of gestation. Of course, women who complain of high blood pressure before pregnancy tend to maintain their hypertensive status even during and after gestation. However, as anticipated in the introductory part, this magical event is accompanied by a physiological drop in blood pressure, which requires a possible therapeutic adjustment or even the suspension of the same until the third quarter.
The greatest risks occur when a previous hypertension is added to that induced by pregnancy, whose causes are to be found in placental hypoperfusion, reduced renal function, as well as in vasospasm and haemoconcentration. One of the most serious clinical pictures associated with pregnancy hypertension is the so-called HELLP syndrome, which stands for the signs and symptoms that characterize it: haemolysis (Haemolysis), elevated liver enzyme values (Elevated Liver enzymes) and reduced platelet values (Low Platelets)
In summary, hypertension in pregnancy can be present in four distinct forms:
Pre-existing chronic hypertension
Gestational hypertension
Preeclampsia / eclampsia
Chronic hypertension + preeclampsia
Risks of hypertension in pregnancy
Hypertension occurs in about 6-8% of all pregnancies and contributes significantly to halting fetal growth, as well as fetal and neonatal morbidity and mortality.
In western societies, in particular, hypertension in pregnancy is the second leading cause of maternal death after thromboembolism, representing about 15% of all causes of death in pregnancy. The pregnant hypertensive is in fact more predisposed to some potentially lethal complications, such as detachment of the placenta, disseminated intravascular coagulation, cerebral hemorrhage and hepatic and renal insufficiency.
Care and prevention of high blood pressure in pregnancy
See also: Drugs for the treatment of gestational hypertension
The picture that emerged from the previous paragraph is rather disturbing; however, talking about increased risk does not necessarily mean talking about high probability. In fact, hypertension in pregnancy can be controlled through appropriate drug therapies; however, it is essential to discover and treat the disorder at an early age, putting in place a whole series of preventive measures.
The therapeutic choice differs in relation to the type of gravidic hypertension and its severity. When the condition is chronic, therefore pre-existing:
in the case of diastolic blood pressure between 90 and 99 mmHg the treatment is essentially behavioral, therefore aimed at the control or the possible reduction of the body weight, the moderation of the food sodium, and the abstention from alcohol, smoking and severe efforts. The risks for mother and fetus are quite low.
If the diastolic pressure reaches and exceeds 100 mmHg, the treatment is pharmacological and based on the use of drugs such as alpha-methyldopa, nifedipine, clonidine or labetalol. Also in this case, the risks for mother and fetus are low but increase as the extent of the hypertensive phenomenon increases.
PLEASE NOTE: in mild forms, the physiological pressure drop that occurs during the first trimesters of pregnancy often gives the possibility to reduce - and sometimes suspend - antihypertensive drugs, which will eventually be taken up again in the last two or three months of gestation.
Some drugs used to treat hypertension are contraindicated in pregnancy; therefore, women of childbearing age who suffer from chronic hypertension should consider the dangers associated with the use of ACE inhibitors, diuretics and Sartans (to be avoided absolutely if they are trying to get pregnant).
In the presence of pre-eclampsia the treatment becomes more articulated, so much so as to foresee a careful control of the patient, the eventual hospitalization with bed rest and the accurate timing of the birth. This event must be seriously considered in front of episodes of fetal distress or worsening maternal conditions. The neonatal complications are mostly related to the need to anticipate the birth in a very early age, in order to limit maternal complications.
The National High Blood Pressure Education Program recommends starting antihypertensive therapy when the minimum pressure is equal to or greater than 100-105 mmHg; the World Health Organization, on the other hand, recommends lowering blood pressure when it is around 170/110 mmHg, in order to protect the mother from the risk of stroke or eclampsia; finally, for other experts, the PAD should be kept between 90 and 100 mmHg.
Magnesium sulfate is the treatment of choice for the prevention and treatment of eclampsia.
PLEASE NOTE: women who have suffered from high blood pressure during pregnancy are at greater risk of returning to being hypertensive with age. The positivity to this test, which in some respects could be considered screening, should therefore be understood as a warning to regularly check one's own pressure (even after the end of pregnancy), and to implement all those healthy behavioral habits necessary to contain the cardiovascular risk (reaching and maintaining a healthy weight, smoking and drug abstention, moderation of alcohol consumption, regular physical activity, optimal daily stress management and balanced diet).
