Steroids Lower MoM Scores

Steroids can falsely lower the MoM score, enough to make doctors think baby is not anemic and does not need a transfusion. This is not the case. Steroids do not treat anemia, and if baby was anemic before the steroids, baby will still be anemic after the steroids. Below are some articles that talk about steroids falsely lowering the MoM scores. Also, Progesterone (oral or as a shot like Makena) can lower the PSV on the MCA scan as well (see the last article listed). 

Antenatal corticosteroid therapy: a comparative study of dexamethasone and betamethasone effects on fetal Doppler flow velocity waveforms.
Urban R1, Lemancewicz A, Przepieść J, Urban J, Kretowska M.
Conclusion: Our results indicate significant decrease in fetal middle cerebral artery impedance at 72 h after maternal administration of the first dose of dexamethasone.

Effect of antenatal betamethasone therapy on maternal-fetal Doppler velocimetry.
Piazze JJ1, Anceschi MM, La Torre R, Amici F, Maranghi L, Cosmi EV.
Conclusion: Betamethasone treatment is associated with a significant, although transient, reduction of MCA PI, especially at gestational ages <32 weeks'.

The combined effect of betamethasone and ritodrine on the middle cerebral artery in low risk third trimester pregnancies.
Piazze J1, Anceschi MM, Cerekja A, Cosmi E, Meloni P, Alberini A, Pizzulo S, Argento T, Cosmi EV.
Conclusion: In low risk pregnancies, betamethasone therapy in the third trimester is related to a significant but transient reduction of MCA PI, which is more pronounced during tocolytic therapy. Although the physiological basis of this effect is currently unclear, it could be related to the local regulation of intracerebral blood flow.

The effect of betamethasone and dexamethasone on fetal heart rate patterns and biophysical activities. A prospective randomized trial.
Rotmensch S1, Liberati M, Vishne TH, Celentano C, Ben-Rafael Z, Bellati U.
Conclusions: Both betamethasone and dexamethasone induce a profound, albeit transient, suppression of fetal heart rate characteristics and biophysical activities in the preterm fetus. However, the effect of betamethasone is more pronounced. Awareness of these phenomena might prevent unwarranted iatrogenic delivery of preterm fetuses.

Effect of antenatal corticosteroid administration on Doppler flow velocity parameters in pregnancies with absent or reverse end-diastolic flow in the umbilical artery.
Müller T1, Nanan R, Dietl J.
In contrast, there was an overall drop of pulsatility in the middle cerebral artery.

The short term fetal cardiovascular effects of corticosteroids used in obstetrics
Amanda Henry, MPH, FRANZCOG, B.Med. (Hons)
Talks about the average MoM drop is 0.3 after steroids.

Effects of maternal dexamethasone administration on fetal Doppler flow velocity waveforms.
Chitrit Y, Caubel P, Herrero R, Schwinte AL, Guillaumin D, Boulanger MC.
Conclusions: The current study finds in healthy fetuses a transient, significant and unexplained decrease in fetal middle cerebral artery impedance on the fourth day following maternal dexamethasone administration. Further basic research and clinical studies including larger sample sizes or pregnancies with fetoplacental dysfunction are needed.

Changes in fetoplacental vessel flow velocity waveforms following maternal administration of betamethasone.
Edwards A, Baker LS, Wallace EM.
Saw a decrease in MoM at 24 hours.

Vaginal versus intramuscular progesterone in the prevention of preterm labor and their effect on uterine and fetal blood flow
Azza A.Abd El Hameed
A statistically significant decrease in fetal MCA-PI was noted after progesterone administration both vaginally and IM.