Uterine and fetal flow velocity waveforms in hypertensive pregnancy: the effect of a single dose of nifedipine

Article Abstract:

Nifedipine is a calcium channel blocker which works by opening blood vessels to reduce blood pressure. It is used to treat patients with coronary artery disease and high blood pressure. It can also be used to treat pregnant women with high blood pressure and to control premature labor. It has been suggested that nifedipine be used as a second line of treatment for high blood pressure in obstetrics cases. Since nifedipine works fast and has few side effects, it is particularly useful in treating high blood pressure which has a sudden onset. It is important to know how nifedipine affects blood flow during pregnancy before the drug can be recommended for routine use. The flow of blood through blood vessels can be measured using Doppler ultrasonography. The short-term effect of a single oral dose of nifedipine (20 milligrams) was studied among 12 women and their fetuses, where the pregnancy was complicated by high blood pressure. The mother's blood pressure, heart rate and blood circulation through the placenta as well as the blood flow patterns and heart rate of the fetus were measured before and after nifedipine administration. One hour after the nifedipine was given, the mother's blood pressure dropped an average of 17 percent and the heart rate increased slightly. The blood flow pattern (diastolic/systolic ratio, S/D ratio) in a major artery supplying the uterus was decreased in seven women and stayed the same in five women. The five women who did not experience a change in S/D blood flow ratio (termed nifedipine nonresponders) delivered earlier, was more likely to undergo cesarean section, and had smaller babies than the women who responded to nifedipine. Since these women also had a higher S/D blood flow ratio before nifedipine intake, it is possible that they had more severe hypertensive disease. The heart rate and blood flow through the umbilical artery or the main artery in the brain of the fetus was not altered by nifedipine. Therefore, a good pregnancy outcome resulted when patients responded to nifedipine, while unchanged S/D ratio was associated with a less favorable outcome. Routine nifedipine use during pregnancy awaits the results of long-term studies. On the basis of this short-term study nifedipine does not appear to be unsafe to the mother or the fetus. (Consumer Summary produced by Reliance Medical Information, Inc.)

Health aspects, Measurement, Blood flow measurement

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Fetal and neonatal effects of treatment with angiotensin-converting enzyme inhibitors in pregnancy

Article Abstract:

Angiotensin-converting enzyme inhibitors are a group of agents used to treat high blood pressure (hypertension), and include the drugs captopril and enalapril. These drugs, often referred to as ACE inhibitors, do not cause many of the side effects associated with other antihypertensive drugs and their use is increasing. However, some reports from animal studies have claimed that they cause problems during pregnancy. This study reviewed reports published prior to January 1, 1990 which examined the effects of angiotensin-converting enzyme inhibitors on human pregnancy and fetal development. Twenty-five publications were found. They involved 85 pregnancies in 81 women who took either captopril (49) or enalapril (35) or both (1) during pregnancy. None of the studies were controlled drug trials. Six of the 85 pregnancies ended early, leaving 79 pregnancies in 76 women of which 76 pregnancies resulted in live births. Oligohydramnios, a deficiency in amniotic fluid, occurred in 11 of the pregnancies and was associated with various fetal abnormalities. Birth weights were below the 10th percentile in 36 percent and below the 5th percentile in 17 percent of the cases where information was available. Respiratory problems were observed in 14 percent of the infants. Seven infants born to mothers who took captopril had an open ductus arteriosus (a passage between the pulmonary artery and the aorta), which required surgical repair. Nine infants suffered from hypotension, or low blood pressure. Five infants died within 30 days of birth, indicating high perinatal mortality. These results show that the use of angiotensin-converting enzyme inhibitors to treat hypertension during pregnancy poses serious threats to the fetus. They should not be used. (Consumer Summary produced by Reliance Medical Information, Inc.)

Abnormalities, Causes of, Complications and side effects, ACE inhibitors, Angiotensin converting enzyme inhibitors, Pregnancy, Pregnancy, Complications of, Pregnancy complications

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Single dose of nifedipine in normotensive pregnancy: nifedipine concentrations, hemodynamic responses, and uterine and fetal flow velocity waveforms

Article Abstract:

The drug nifedipine is administered to pregnant women to reduce elevated blood pressure (BP) and inhibit untimely uterine contractions. The effects of this agent on the placenta and fetus were studied in 10 healthy women who were scheduled for elective cesarean delivery. On the evening before surgery, the women underwent fetal heart rate monitoring and ultrasound measurement of blood flow in the uterine and umbilical vessels. Prior to cesarean, nifedipine (two 10 milligram tablets) was administered to the women and a second set of ultrasound studies was performed; additional tests were conducted immediately after delivery. Results showed that the drug caused decreases in maternal systolic and diastolic BP components, and in mean arterial pressure. A decrease was also observed in the ratio of systolic to diastolic blood flow velocity in the uterine artery (which delivers blood to the uterus). No changes were noted in umbilical vessel blood flow velocity or fetal heart rate. Within three hours after taking nifedipine, drug levels in the fetal circulation were approximately three-quarters as high as those in the maternal circulation. All infants were healthy. Because the drug crosses into the placenta rapidly, longer-term studies regarding its effects should be carried out. (Consumer Summary produced by Reliance Medical Information, Inc.)

Pregnant women

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