Pregnancy Timeline & Milestone Guide
Structured week-by-week clinical investigations, maternal physiological adaptations, fetal biometry milestones, and tactical father action plans aligned with SOGC and Manitoba guidelines.
First Trimester (Weeks 1 to 13) • Embryogenesis & Screening
Implantation and Blastocyst Differentiation
Blastocyst completes implantation into the secretory endometrium.
Primitive Cardiac Tube & Neural Tube Closure
Primitive tubular heart begins rhythmic contractions (100–115 bpm), detectable on transvaginal ultrasound (TVUS).
Organogenesis & Rapid Brain Neurogenesis
All essential external and internal structures have been laid down; embryonic period concluding soon.
Transition from Embryo to Fetus
The embryonic period has officially ended; now designated a fetus.
End of First Trimester & Reflex Architecture
Fetal reflexes active: spontaneous curling of toes, opening/closing of mouth, swallowing amniotic fluid.
Second Trimester (Weeks 14 to 27) • Rapid Growth & Anatomy
Musculoskeletal Ossification & Fine Motor Movement
Skeleton undergoing active endochondral ossification, visible on ultrasound.
Anatomy Milestone & Sensory System Awakening
Cochlear and auditory structures functionally innervated; fetus responds to maternal cardiovascular sounds and acoustic stimuli.
Viability Threshold & Canalicular Lung Stage
Threshold of legal and physiological viability: intensive neonatal resuscitation possible in tertiary NICUs (such as HSC Winnipeg NICU).
Third Trimester (Weeks 28 to 41+) • Viability, Maturation & Labour Prep
Third Trimester Entry & Central Nervous System Maturation
Fetus opens and closes eyelids; pupils demonstrate light reflex.
Subcutaneous Fat Accumulation & Thermal Regulation Prep
White adipose tissue accounts for ~8% of fetal body weight, smoothing skin wrinkles and providing neonatal thermal insulation.
Near-Term Maturation & Group B Strep Milestone
Lungs nearly fully mature with adequate lecithin-to-sphingomyelin ratio and phosphatidylglycerol in amniotic fluid.
Term Maturation & Surfactant Surge
Lungs fully primed for extrauterine gaseous exchange.
Estimated Due Date (EDD) Arrival
Fetus is fully prepared for atmospheric transition; placenta continues to provide adequate gas exchange and nutrition.