Blood pressure and heart frequency changes in pregnancy - Value of hypertonia

The mean arterial blood pressure is decreased during the first two trimeste rs of pregnancy and increases to preconceptional Values during the last wee ks of gestation. The heart rate increases during the whole course of pregna ncy. During late gestation fewer patients show an increase in diastolic blo od pressure and heart rate in the standing position. A fall in heart rate w as only seen in this period. A fall in mean arterial blood pressure during standing is not related to the blood pressure in the supine position during the whole course of pregnancy. The hypotensive symptoms are twice as frequ ent during early pregnancy compared to late pregnancy. Headaches, fatigue a nd cold extremities are the most usual complaints. The frequency and intens ity of these th ree symptoms decrease during gestation. Blood pressure in t he supine position is reduced in symptomatic pregnant women. However, the o ccurrence of these symptoms is not correlated to the fall in blood pressure in the standing position. The Birth-weight is not influenced by blood pres sure in the supine position, but depends on the fail in blood pressure duri ng standing. Pregnant women with a more pronounced fall in blood pressure g ive birth to newborns with a lower birthweight. These results imply a hithe rto unknown cause of intrauterine growth restriction.