Pregnancy

Overview

Pregnancy tracking records the user's pregnancy status as a time-bounded sample, with start and end dates indicating the pregnancy period. This contextual information is critical for interpreting other health data during pregnancy, as many physiological parameters change significantly during gestation. When pregnancy is logged, the Health app and Cycle Tracking can adjust predictions and interpretations accordingly.

The sample represents an ongoing pregnancy state rather than a discrete event. Users typically log pregnancy after confirmation (positive pregnancy test, clinical confirmation) and the sample may be updated as the estimated due date is refined through clinical dating.

Health Significance

Pregnancy status profoundly affects health data interpretation:

• Vital sign context: Resting heart rate increases 10-20 bpm during pregnancy; blood pressure patterns change across trimesters
• Weight tracking: Expected weight gain varies by trimester and pre-pregnancy BMI; tracking monitors healthy progression
• Activity adjustments: Exercise recommendations differ during pregnancy; heart rate zones and exertion targets should be adjusted
• Sleep pattern changes: Sleep disturbances, position changes, and duration needs evolve throughout pregnancy
• Symptom normalization: Many symptoms (nausea, fatigue, heartburn) are expected during pregnancy
• Medication safety: Critical context for medication decisions and teratogenic risk assessment
• Mental health monitoring: Prenatal anxiety and depression screening is enhanced by baseline mood data
• Fertility tracking cessation: Menstrual cycle predictions and ovulation tracking pause during pregnancy

Clinical Interpretation Guidelines

When reviewing health data with pregnancy context:

• Gestational dating:
  • Pregnancy weeks counted from last menstrual period (LMP), not conception
  • Due date calculation: LMP + 280 days (40 weeks)
  • Clinical dating ultrasound may adjust estimated due date
• Trimester-specific considerations:
  • First trimester (weeks 1-12): Fatigue, nausea common; miscarriage risk highest; weight gain minimal
  • Second trimester (weeks 13-26): Energy often improves; weight gain accelerates; fetal movement begins
  • Third trimester (weeks 27-40): Fatigue returns; sleep disruption increases; weight gain continues
• Vital sign expectations:
  • Heart rate: Increases progressively, peaks around 32 weeks
  • Blood pressure: Typically decreases mid-pregnancy, rises toward baseline in third trimester
  • Respiratory rate: May increase slightly
• Activity data interpretation:
  • Step counts and activity may naturally decrease as pregnancy progresses
  • Exercise tolerance varies; some reduction is physiologically normal
• Weight monitoring:
  • First trimester: 1-4 lbs typical gain
  • Second and third trimester: ~1 lb/week typical for normal BMI
  • Total recommended gain varies by pre-pregnancy BMI (25-35 lbs for normal BMI)

Caveats & Limitations

• Does not capture pregnancy-specific clinical data (ultrasound findings, lab results, complications)
• Gestational age and due date may not be stored in sample; requires external reference
• Multiple pregnancies (twins, etc.) are not differentiated from singleton
• Pregnancy loss or termination requires manual sample end date adjustment
• Does not track pregnancy complications (gestational diabetes, preeclampsia, etc.)
• Trimester stage is calculated, not explicitly stored
• Postpartum period is not explicitly tracked after pregnancy sample ends
• Users may not update end date promptly after delivery or loss
• Does not capture mode of delivery or birth outcomes