The Role of Laboratory Medicine for Health During Pregnancy.

Pregnancy produces profound physiological changes that increase in significance as it progresses. These changes include hormonal changes, metabolic changes, increases of plasma volume up to 50%, alterations to the balance of the coagulation system in favour of clotting, and GFR increases to a peak 50% above prepregnancy levels. Since healthy physiological changes occur during pregnancy, different reference intervals may be needed. First antenatal screens usually include Complete blood count, Blood group and antibody screen, rubella antibody status, syphilis serology, Hepatitis B serology and HIV abs testing. Additional testing in early pregnancy may be added to the first antenatal screen such as varicella, Chlamydia and vitamin D tests. The most important test in the second antenatal testing screen is gestational diabetes screening and protein detection in urine to rule out preeclampsia. Screening for Down syndrome, other chromosomal abnormalities and neural tube defects is recommended for all pregnant women above the age of 35 years. Additionally, 37 weeks into pregnancy, a swab to detect Group B streptococcal (GBS) infection is recommended.