Are recurrent episodes of RFM a real risk for stillbirth?
If ‘pathological’ RFMs is preterminal, it would seem unlikely that
babies repeatedly become very sick and then recover. Indeed, not all
evidence supports recurrent ‘episodes’ as a risk 7,9,
and not all national (eg US) guidelines support the concept. Recently,
in a retrospective study including >8000 pregnancies with
RFMs, Turner et 1 reported that two or more episodes
might increase stillbirth risk (aOR 4.96; 0.98-24.98) when compared to
one episode, yet not when compared to no episodes. In a case control
study of 660 stillbirths, Heazell et al 10 reported
that women who had experienced stillbirth were more likely than controls
to report multiple episodes of RFMs since 26 weeks (OR for three or more
episodes 5.11 (3.22 to 8.10)). Ultrasound based studies show conflicting
results but generally report a small excess of markers of FGR.
Do these establish recurrent RFMs as an independent risk factor? It
constituted a cornerstone of the strategies of the trials that failed to
reduce stillbirth. There is huge potential for reverse causality and
bias. Women with high-risk pregnancies, or indeed abnormal scan
findings, would be expected to be more vigilant, be scanned more often
and have SGA babies more often. Women interviewed after a stillbirth may
be affected by recall bias. Finally, what is the definition of
‘recurrent’? No analyses differentiate between episodes of RFM and
presentations of RFM. Why does this matter? Many clinicians will have
seen pregnancies with RFMs and a normal CTG who, less than two days
later and usually with continued RFMs, present with the baby in extremis
or tragically dead. CTG changes are preterminal but the temporal
relationship with RFMs is not consistent. Hence it is worth encouraging
re-presentation and repeating the CTG if RFMs continue because the baby
may be very sick but the CTG is not yet abnormal. This is not recurrent
episodes of RFMs: it is recurrent presentations of one episode.