Closing the Evidence Gaps in Trimester-Specific Pregnancy Reference Intervals for Biochemical Markers of Health and...

Pregnancy induces a series of physiological adaptations, making accurate interpretation of clinical laboratory tests essential for maternal and fetal health. However, significant knowledge gaps persist in understanding how gestation affects circulating blood biochemistry, leading to potential clinical misinterpretations and underscoring the need for updated reference intervals in contemporary obstetric populations.

A cohort of approximately 135 healthy pregnant individuals was recruited with informed consent. Participants were excluded based on the use of prescribed medications, multiple gestations, age above 40 years, a history of chronic illness, or presence of acute illness during pregnancy. Blood samples were collected at 4 time points: 0 to 13 weeks, 14 to 27 weeks, 28 to 42 weeks, and 1 to 3 months postpartum. A total of 24 biochemical markers were analyzed. Statistically significant differences across gestational and early postpartum periods were assessed, and trimester-specific reference intervals were established.

Of the 24 biochemical markers assessed, 17 exhibited statistically significant variations across gestation and the early postpartum period. Notably, albumin, total protein, creatinine, urea, uric acid, free thyroxine (FT4), and anemia markers showed significant decreases in late gestation compared to postpartum. Conversely, alkaline phosphatase, cholesterol, and triglycerides demonstrated substantial increases during gestation, followed by a marked decrease in the postpartum period.

This study provides comprehensive biochemical profiling of healthy pregnant individuals in Canada across gestation and the postpartum period. The findings highlight substantial alterations in circulating blood biochemistry during pregnancy, emphasizing the need for trimester-specific reference intervals to ensure accurate clinical test interpretation. Without such gestational age-specific benchmarks, maternal-fetal care standards remain suboptimal.