Serentil is a tranquilizer.  I couldn't find anything in Hale '97 on this
drug,  although there is a section in his book on p. 123 on chlorpromazine.
I quote from "Drugs in Pregnancy and Lactation":

Risk Factor C

Fetal Risk Summary:

Mesoridazine is a piperidyl phenothiazine.  Phenothiazines readily cross
the placenta.  No specific information on its use in pregnancy has been
located.  Although occasional reports have attempted to link various
phenothiazine compounds with congenital malformations,  the bulk of the
evidence indicates that these drugs are safe for the mother and fetus  (see
Chlorpromazine).

Breast Feeding Summary:

No reports describing the excretion of mesoridazine into breast milk have
been located.  The AAP classsifies mesoridazine as an agent whose effect on
the nursing infant is unknown but may be of concern.

Loyann Waber