Strengths and limitations
Studies examining the use of biologics in pregnancy have been limited
due to small sample size and the rare outcomes of interest. To our
knowledge this is the largest cohort of pregnancies exposed to biologics
collated to date. This review was based on a pre-published protocol on
PROSPERO and followed the PRISMA guidelines. This review allows areas of
future research to be highlighted that are currently lacking, primarily
elucidating the links with preterm birth, maternal infection risk as
well as exploring likely protective effects of these medications against
uncontrolled disease activity. There are several limitations to this
study, our search included English only literature. Disparities in the
measurement criteria e.g.: birth weight, infection criteria and even the
diagnostic criteria for congenital malformation make meta-analysis on
this topic difficult with an already small sample being made smaller by
misusing the appropriate definition and criteria. Additionally, the
recording of concomitant medications, particularly corticosteroids,
dosing and pregnancy outcomes which can differ between studies is
imprecise at best. Pregnancy outcomes in this population can be
influenced by the activity of the underlying disease state
peri-conceptually and during pregnancy which can be difficult to
accurately collate in these observational studies and difficult to
control for by using a “disease matched cohort” when matched by
diagnosis only.
We have expanded on the previous reviews by increasing the pool of data
to include peer reviewed cohort studies and case
series11,12,21 with statistical analysis of
proportions rather than odds ratio. Another novel approach that we have
taken was allowing comparisons across three populations; the treated,
disease matched and disease free. We also performed sub analysis by
biologic type and disease type where appropriate.