AMERICAN JOURNAL OF PERINATOLOGY/VOLUME 7, NUMBER 3
July 1990
EFFECT OF NIFEDIPINE ON FETAL HEART RATE IN THE TREATMENT OF SEVERE PREGNANCY-INDUCED HYPERTENSION Samuel Lurie, M.D., Katerina Fenakel, M.D., and Adi Friedman, M.D.
ABSTRACT The effect of lowering the maternal blood pressure with sublingual nifedipine on the fetal heart rate was studied in 51 patients with severe pregnancy-induced hypertension. No fetal heart rate abnormalities were observed, while achieving an excellent control of blood pressure.
METHODS
Fifty-one patients having severe pregnancy-induced hypertension in the third trimester were treated with nifedipine. The patients were included in this study if the blood pressure values were of 160/110 mmHg or higher, measured on at least two occasions, 2 hours apart. The blood pressure was measured in the lateral position after complete bed rest for 20 minutes. Treatment with nifedipine was started with a 10 mg capsule given sublingually. If blood pressure values after 20 minutes were still
160/110 mmHg or higher, the sublingual dose was repeated 20 and 40 minutes later. Thereafter, oral nifedipine was administered until delivery. Prior to the administration of nifedipine, fetal heart rate monitoring by a cardiotocograph was started and thereafter the monitoring continued for 120 minutes. Twenty-three patients (45.1%) had growth-retarded fetuses when the treatment was started. An intrauterine growth retardation was defined when ultrasonographic estimation of fetal weight was less than the 10th percentile for its gestational age.
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The major hazard of pregnancy-induced hypertension to the fetus results from decreased placental perfusion. Thus, it is not surprising that there has been an apprehension about the use of hypotensive agents in pregnancy because of the drastic fall in blood pressure that adds to the hazardous effect on the fetus. Intravenous hydralazine, a drug most commonly used in control of severe pregnancy-induced hypertension, was shown to cause fetal heart rate abnormalities coinciding with a fall in blood pressure.1 Unlike hydralazine, nifedipine does not act drastically: the blood pressure starts to decrease after 10 minutes and the duration of the decrease lasts 20 minutes. Thereafter, the blood pressure stabilizes at values that are close to normal for about 6 hours.2 Nifedipine is widely used for treatment of severe pregnancy-induced hypertension in our department. The objective of this study was to assess the fetal heart rate changes following sublingual administration of nifedipine.
RESULTS
Effective control of blood pressure was achieved in all but one patient. This patient was transferred to intravenous hydralazine treatment after a 24-hour trial of sublingual and oral nifedipine. No fetal heart rate abnormalities were observed in all 51 cases. A fetal heart rate trace showing normal pattern coinciding with a fall in blood pressure is shown in Figure 1. DISCUSSION
Maternal hypotension decreases the uterine blood flow, which subsequently produces hypoxic stress on the fetus and results in fetal heart rate abnormality. Since nifedipine was shown to lower the blood pressure without reducing the uteroplacental blood flow,3 we assumed that it will not have adverse
Department of Obstetrics and Gynecology, Kaplan Hospital, Rehovot, Israel Reprint requests: Dr. Lurie, Department of Obstetrics and Gynecology, Kaplan Hospital, 76100 Rehovot, Israel Copyright © 1990 by Thieme Medical Publishers, Inc., 381 Park Avenue South, New York, NY 10016. All rights reserved.
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AMERICAN JOURNAL OF PERINATOLOGY/VOLUME 7, NUMBER 3 July 1990
effects on fetal heart rate. Our results demonstrate that administration of nifedipine does not cause an abnormal fetal heart rate even in fetuses with intrauterine growth retardation. In comparison, hydralazine caused fetal heart rate abnormalities in 19 of 33 patients (57.6%); 13 of those 19 (68.4%) were fetuses with intrauterine growth retardation.1 The results showed that nifedipine-induced lowering of maternal blood pressure does not cause fetal heart rate abnormalities. They are in accordance with previously reported works that demonstrated that treatment of pregnancy-induced hypertension with the calcium channel blocker nifedipine is not associated with serious treatment-ascribable side effects in the babies born to mothers receiving it.4.5
286
REFERENCES 1. Vink CJ, Moodley J, Philpott RH: Effect of dihydralazine on the fetus in the treatment of maternal hypertension. Obstet Gynecol 55:519-522, 1980 2. Frishman WH, Weinberg P, Kimmel MB, et al: Calcium entry blockers for the treatment of severe hypertension and hypertensive crisis. Am J Med 77 (Suppl 2B):35-45, 1984 3. Lindow SW, Davies N, Davey DA, Smith JA: The effect of sublingual nifedipine on uteroplacental blood flow in hypertensive pregnancy. Br J Obstet Gynaecol 95:1276— 1281, 1988 4. Walters BNJ, Redman CWG: Treatment of severe pregnancy associated hypertension with the calcium antagonist Nifedipine. Br J Obstet Gynaecol 91:330-336, 1984 5. Forman A, Andersson KE, Ulmsten U: Inhibition of myometrial activity by calcium antagonist. Semin Perinatol 5:288-294, 1981
Downloaded by: Universite Laval. Copyrighted material.
Figure 1. Fetal heart rate trace during administration of nifedipine while recording the blood pressure. The arrow indicates the time of drug administration.
July 1990
EFFECT OF NIFEDIPINE ON FETAL HEART RATE IN THE TREATMENT OF SEVERE PREGNANCY-INDUCED HYPERTENSION Samuel Lurie, M.D., Katerina Fenakel, M.D., and Adi Friedman, M.D.
ABSTRACT The effect of lowering the maternal blood pressure with sublingual nifedipine on the fetal heart rate was studied in 51 patients with severe pregnancy-induced hypertension. No fetal heart rate abnormalities were observed, while achieving an excellent control of blood pressure.
METHODS
Fifty-one patients having severe pregnancy-induced hypertension in the third trimester were treated with nifedipine. The patients were included in this study if the blood pressure values were of 160/110 mmHg or higher, measured on at least two occasions, 2 hours apart. The blood pressure was measured in the lateral position after complete bed rest for 20 minutes. Treatment with nifedipine was started with a 10 mg capsule given sublingually. If blood pressure values after 20 minutes were still
160/110 mmHg or higher, the sublingual dose was repeated 20 and 40 minutes later. Thereafter, oral nifedipine was administered until delivery. Prior to the administration of nifedipine, fetal heart rate monitoring by a cardiotocograph was started and thereafter the monitoring continued for 120 minutes. Twenty-three patients (45.1%) had growth-retarded fetuses when the treatment was started. An intrauterine growth retardation was defined when ultrasonographic estimation of fetal weight was less than the 10th percentile for its gestational age.
Downloaded by: Universite Laval. Copyrighted material.
The major hazard of pregnancy-induced hypertension to the fetus results from decreased placental perfusion. Thus, it is not surprising that there has been an apprehension about the use of hypotensive agents in pregnancy because of the drastic fall in blood pressure that adds to the hazardous effect on the fetus. Intravenous hydralazine, a drug most commonly used in control of severe pregnancy-induced hypertension, was shown to cause fetal heart rate abnormalities coinciding with a fall in blood pressure.1 Unlike hydralazine, nifedipine does not act drastically: the blood pressure starts to decrease after 10 minutes and the duration of the decrease lasts 20 minutes. Thereafter, the blood pressure stabilizes at values that are close to normal for about 6 hours.2 Nifedipine is widely used for treatment of severe pregnancy-induced hypertension in our department. The objective of this study was to assess the fetal heart rate changes following sublingual administration of nifedipine.
RESULTS
Effective control of blood pressure was achieved in all but one patient. This patient was transferred to intravenous hydralazine treatment after a 24-hour trial of sublingual and oral nifedipine. No fetal heart rate abnormalities were observed in all 51 cases. A fetal heart rate trace showing normal pattern coinciding with a fall in blood pressure is shown in Figure 1. DISCUSSION
Maternal hypotension decreases the uterine blood flow, which subsequently produces hypoxic stress on the fetus and results in fetal heart rate abnormality. Since nifedipine was shown to lower the blood pressure without reducing the uteroplacental blood flow,3 we assumed that it will not have adverse
Department of Obstetrics and Gynecology, Kaplan Hospital, Rehovot, Israel Reprint requests: Dr. Lurie, Department of Obstetrics and Gynecology, Kaplan Hospital, 76100 Rehovot, Israel Copyright © 1990 by Thieme Medical Publishers, Inc., 381 Park Avenue South, New York, NY 10016. All rights reserved.
285
AMERICAN JOURNAL OF PERINATOLOGY/VOLUME 7, NUMBER 3 July 1990
effects on fetal heart rate. Our results demonstrate that administration of nifedipine does not cause an abnormal fetal heart rate even in fetuses with intrauterine growth retardation. In comparison, hydralazine caused fetal heart rate abnormalities in 19 of 33 patients (57.6%); 13 of those 19 (68.4%) were fetuses with intrauterine growth retardation.1 The results showed that nifedipine-induced lowering of maternal blood pressure does not cause fetal heart rate abnormalities. They are in accordance with previously reported works that demonstrated that treatment of pregnancy-induced hypertension with the calcium channel blocker nifedipine is not associated with serious treatment-ascribable side effects in the babies born to mothers receiving it.4.5
286
REFERENCES 1. Vink CJ, Moodley J, Philpott RH: Effect of dihydralazine on the fetus in the treatment of maternal hypertension. Obstet Gynecol 55:519-522, 1980 2. Frishman WH, Weinberg P, Kimmel MB, et al: Calcium entry blockers for the treatment of severe hypertension and hypertensive crisis. Am J Med 77 (Suppl 2B):35-45, 1984 3. Lindow SW, Davies N, Davey DA, Smith JA: The effect of sublingual nifedipine on uteroplacental blood flow in hypertensive pregnancy. Br J Obstet Gynaecol 95:1276— 1281, 1988 4. Walters BNJ, Redman CWG: Treatment of severe pregnancy associated hypertension with the calcium antagonist Nifedipine. Br J Obstet Gynaecol 91:330-336, 1984 5. Forman A, Andersson KE, Ulmsten U: Inhibition of myometrial activity by calcium antagonist. Semin Perinatol 5:288-294, 1981
Downloaded by: Universite Laval. Copyrighted material.
Figure 1. Fetal heart rate trace during administration of nifedipine while recording the blood pressure. The arrow indicates the time of drug administration.
