Doppler velocimetry of the uterine, umbilical and fetal middle cerebral arteries in pregnant women undergoing tocolysis with oral nifedipine.
OBJECTIVE
To evaluate Doppler velocimetry (resistance index (RI) and peak systolic velocity (PSV)) in the maternal-fetal circulation before and 5 and 24 h after tocolysis with oral nifedipine.


METHODS
This was a prospective, observational, analytic cohort study performed in 47 pregnant women undergoing nifedipine tocolysis, each subject acting as her own control. Doppler assessment of uterine, umbilical and fetal middle cerebral (MCA) arteries was performed before and 5 and 24 h after an initial 20-mg sublingual dose, which was repeated twice at 20-min intervals if contractions failed to diminish. The maintenance dose consisted of 20 mg orally every 6 h for 24 h up to a total of 100-120 mg nifedipine. We analyzed whether there was a time effect and compared values at the different time-points.


RESULTS
The MCA-RI had decreased significantly after 24 h of tocolysis (0 h = 0.85; 5 h = 0.85; 24 h = 0.81; P = 0.001), with no differences in uterine or umbilical arteries or in the MCA to umbilical artery ratio. The MCA-PSV had reduced significantly after 5 h (0 h = 41.5 cm/s; 5 h = 34.7 cm/s; P = 0.001), returning close to baseline levels between 5 and 24 h. The PSV increased significantly between 5 and 24 h in the right uterine artery (5 h = 55.1 cm/s; 24 h = 65.0 cm/s; P = 0.037) and in the umbilical artery (5 h = 28.4 cm/s; 24 h = 33.1 cm/s; P = 0.038).


CONCLUSIONS
Nifedipine tocolysis is associated with a reduction in RI in the MCA but not in the uterine or umbilical arteries, a reduction in PSV in the MCA after 5 h but returning to baseline within 24 h, and an increase in PSV between 5 and 24 h in the umbilical and right uterine arteries.
Lima
M M De S
MM
Instituto de Medicina Integral Professor Fernando Figueira, Department of Maternal Care, Fetal Medicine Division, Recife, Pernambuco, Brazil. mmslnet@terra.com.br
Souza
A S R
AS
Diniz
C
C
Porto
A M F
AM
Amorim
M M R
MM
Moron
A F
AF
D000293:Adolescent; D000328:Adult; D001783:Blood Flow Velocity / Q000187:drug effects / Q000502:physiology; D005260:Female; D005865:Gestational Age; D006801:Humans; D008431:Maternal-Fetal Exchange; D020768:Middle Cerebral Artery / Q000187:drug effects* / Q000196:embryology / Q000503:physiopathology; D009543:Nifedipine / Q000627:therapeutic use*; D007752:Obstetric Labor, Premature / Q000188:drug therapy / Q000517:prevention & control; D011247:Pregnancy; D015145:Tocolysis / Q000379:methods; D015149:Tocolytic Agents / Q000627:therapeutic use*; D018615:Ultrasonography, Doppler, Color; D016216:Ultrasonography, Prenatal; D014469:Umbilical Arteries / Q000187:drug effects* / Q000196:embryology / Q000503:physiopathology; D055988:Uterine Artery / Q000187:drug effects* / Q000196:embryology / Q000503:physiopathology; D055815:Young Adult
D015149:Tocolytic Agents; D009543:Nifedipine