[Fetal lung maturity and fetal flowmetry changes]

To verify whether in high risk pregnancies, fetuses with altered Doppler flow velocimetry waveforms (FVW) are associated with both biochemical and/or biophysical changes in the amniotic fluid (AF) lung surfactant.

Hundred-eight high risk pregnancies were considered on the basis of a complete Doppler velocimetry study performed within 24 hrs before amniocentesis and delivery within 1 week from amniocentesis. From this group, 22 pregnancies were recruited as altered FVW cases on the basis of simultaneous alteration of Umbilical Artery Pulsatility Index (UA PI), and UA PI/MCA PI (Middle Cerebral Artery Pulsatility Index) ratio (UA/MCA); in all altered FVW group cases the Mean Uterine Artery Resistance Index (Ut RI) was also altered. Amniotic fluid samples obtained by ultrasound guided amniocentesis were analysed for FLM within 24 hours from collection. Pulmonary maturity was determined by planimetric lecithin/sphingomyelin ratio (L/S), phosphatidylglycerol (PG) and the lamellar bodies count (LBs).

When FLM parameters were regressed versus FVW in the whole study group, we found a significant negative correlation between UA/MCA and L/S (r = -0.19, p < 0.05). No significant correlations were found between FVW indices and LBs. When we compared FLM parameters for gestational age subgroups (23-32 wks, > 33 wks), L/S values were significantly higher in patients with normal FVW indices in comparison to pathologic FVW pregnancies for gestational ages > 33 wks. This was reflected by a negativè correlation between FVW and FLM (UA/MCA vs. L/S r = -0.54, p < 0.02; UA/MCA vs. PG, r = -0.60, p < 0.01).

Our data suggest that fetuses with an UA/MCA ratio > 95 degrees are not protected from neonatal RDS, as usually felt, but show a delay in FLM, particularly in pregnancies > 33 wks.