Effect of Antenatal Steroid on Pulmonary Artery Blood Flow

After internal review board approval, 126 consecutive patients attending the antenatal care clinic of Kasr Alainy Hospital, part of Cairo university hospitals will be recruited in this study. All patients will sign informed consent.

Patients included in the study will be 20-38 years of age, have an indication for elective caesarean section. Patients will be excluded if they are hypertensive, diabetic or have any disorder that may be aggravated by administration of steroids, women with systemic infection including tuberculosis or sepsis, any fetal congenital anomalies (affecting the fetal heart, lungs, and circulation), history of rupture membranes, or suspected chorioamnionitis, intrauterine growth retardation (IUGR), and intrauterine fetal demise (IUFD).

Patients will be randomized on 37 weeks and 6 days gestation by the nurse attending the clinic using a computer generated randomization table, and a closed envelope system will be used. Patients will be equally divided into two groups. Patients in group (A) will receive two doses of 12mg betamethasone ( Dipropfos ® SCHERING-PLOUGH; Kenilworth, New Jersey, USA) intramuscularly (IM) 24 hours apart, while group (B) patients will receive a saline placebo injection in the same regimen.

Ultrasound examination will be done where all patients will lie down in a semi-recumbent position, and the ultrasound will be performed by an expert ultrasonographer, with expert training in fetal echocardiography. The ultrasound specialist will be blinded to which study arm the patients belongs. The abdominal probe of the ultrasound machine (voluson730; kretz,Zipf,Austria) will be placed so that the fetal chest will be in a transverse section, giving us the four chamber view of the fetal heart. The color Doppler will then be switched on, and the fetal pulmonary artery will be identified. The measurements will be taken from the middle segment of the pulmonary artery just after the first bifurcation of the pulmonary branch (just after crossing the aortic arch). We will obtain our measurements from either the right or left pulmonary arteries, whichever is easier according to fetal position, as there is no difference between the values obtained from either according to the work done by Rasanen et al.

The pulsatility index (PI), resistance index (RI), systolic/diastolic ratio (SD), and the acceleration-time/ejection-time ratio (At/Et) will be determined in all cases after recruitment, just before the administration of the drug (betamethasone / placebo), 24 hours after the last dose, and on the day of elective Cs. Caesarean section will be performed 7 days after the last dose of betamethasone, and a senior neonatologist will attend the birth, document Apgar score, and any neonatal respiratory distress.

A sample size was calculated where the difference in the mean pulsatility index (PI) before and after administration of antenatal steroids for the middle segment of the fetal pulmonary artery was 0.42 in a previous study by Bartha et al, and the standard deviation was set as 0.79. The Type I error probability was set at 0.05, and the power at 80%. This gave us 57 patients in each arm, and allowing for dropout rate of 10%, 63 patients will be recruited in each arm of the study, as the ratio between both study and control was 1:1. PS Power and Sample size Calculations software, Versionv2.1.30 for MS Windows, was used to calculate sample size Dupont and Vanderbilt, USA).