diff --git a/src/aliby/baby_sitter.py b/src/aliby/baby_sitter.py
index 064b3748f432d147e627da4954b6c03c07ae389b..386e312b3d06edc13916829fabc6a24618dd6d9f 100644
--- a/src/aliby/baby_sitter.py
+++ b/src/aliby/baby_sitter.py
@@ -15,24 +15,30 @@ class BabyParameters(ParametersABC):
     def __init__(
         self,
         modelset_name,
+        pixel_size,
         clogging_thresh,
         min_bud_tps,
         isbud_thresh,
+        session,
     ):
         """Initialise parameters for BABY."""
         self.modelset_name = modelset_name
+        self.pixel_size = pixel_size
         self.clogging_thresh = clogging_thresh
         self.min_bud_tps = min_bud_tps
         self.isbud_thresh = isbud_thresh
+        self.session = session
 
     @classmethod
     def default(cls, **kwargs):
         """Define default parameters; kwargs choose BABY model set."""
         return cls(
             modelset_name=get_modelset_name_from_params(**kwargs),
+            pixel_size=0.182,
             clogging_thresh=0.75,
             min_bud_tps=3,
             isbud_thresh=0.5,
+            session=None,
         )
 
     def update_baby_modelset(self, path: t.Union[str, Path, t.Dict[str, str]]):
@@ -78,9 +84,11 @@ class BabyRunner(StepABC):
         else:
             brain = modelsets.get(
                 modelset_name,
+                pixel_size=parameters.pixel_size,
                 clogging_thresh=parameters.clogging_thresh,
                 min_bud_tps=parameters.min_bud_tps,
                 isbud_thresh=parameters.isbud_thresh,
+                session=parameters.session,
             )
         self.crawler = BabyCrawler(brain)
         self.brightfield_channel = self.tiler.ref_channel_index