Randomised Controlled Trial of Atenolol and Pindolol in Human Pregnancy: Effects on Fetal Haemodynamics

Objective: To compare the effects of uteroplacental circulation of two beta adrenoceptor blockers, atenolol (cardioselective) and pindolol (non-selective with intrinsic sympathomimetic activity).

Design: Controlled double blind double dummy study.

Setting: Departments of obstetrics and gynaecology in two Swedish university hospitals.

Subjects: 29 women with pregnancy induced hypertension in the third trimester, 13 randomised to atenolol and 16 to pindolol.

Main Outcome Measures: Pulsatility index in fetal aorta, umbilical artery, and maternal arcuate artery. Volumetric blood flow in fetal aorta and umbilical vein.

Results: Mean arterial blood pressure decreased by 9.0 (95% confidence interval -13.0 to -5.0) mm Hg in the atenolol group and by 7.8 (-11.4 to -4.2) mm Hg in the pindolol group. During atenolol treatment the pulsatility index increased significantly from 1.82 (SD 0.20) to 2.07 (0.32) in the fetal thoracic descending aorta, from 1.44 (0.28) to 1.79 (0.27) in the abdominal aorta, and from 0.93 (0.17) to 1.05 (0.19) in the umbilical artery; the volumetric blood flow in the umbilical vein decreased from 106 (28.8) to 84 (22.6) ml/min/kg. No such changes were seen after treatment with pindolol. Birth weight was similar in the two groups but placental weight was significantly different (529 (122) g in atenolol group v 653 (136) g in pindolol group; p = 0.03).

Conclusion: The hypotensive effect was similar with both drugs, but only the beta 1 blocker atenolol had significant effects on fetal haemodynamics, although within normal ranges. The implications of these findings can be only speculative, but negative fetal consequences of beta 1 adrenoceptor blockade cannot be excluded.