Postpartum Lab Tests After Childbirth: Why They Are Used and What the Results Mean

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What Happens

Giving birth can be a joyous experiences for a woman, but it can also be one of the most challenging experiences physically. Sometimes, the new mother might lose blood volume during the birth. A CBC (complete blood count) is the primary among postpartum lab tests ordered following childbirth. It would be expected that the white blood cell count would increase temporarily due to the stress of giving birth and that the hemoglobin and hematocrit would decrease.

The hemoglobin is a measurement of the oxygen transport mechanism of red blood cells. The portion of the hemoglobin molecule that can bind to oxygen includes iron, so the capacity to transport oxygen is dependent on the blood iron levels. Normal hemoglobin levels for an adult woman is 12-16 gr/dl.

Hematocrit levels are a percentage of cells to plasma or the liquid portion of blood. Normal hematocrit levels are 38-46% for women.

Other blood testing is usually performed prior to giving birth. These would include a blood type and Rh to identify whether the mom may be a candidate for Rhogam following childbirth. Rhogam is given following childbirth when the baby’s blood type is Rh positive and the mom’s blood type is Rh negative.

Lab Tests for the Baby

The baby’s cord blood is collected from the umbilical cord right after birth. Postpartum lab tests following childbirth include cord blood testing. The components of this test include a blood type and direct coombs. This test is done when there is a possibility of incompatible blood type with the mother.

The most commonly seen problems involve ABO or Rh incompatibility. If the mother is Rh negative and the baby is Rh positive, the mother’s naturally occurring antibody will attach itself to the baby’s red blood cells. The more of mom’s antibodies that attach to the baby’s cells, the greater the potential for rupturing the baby’s cells. Ruptured cells release bilirubin into the baby’s blood which must be cleared by the baby. Often babies will appear to be jaundiced following the release of bilirubin from red blood cells.

An ABO incompatibility is similar. A type O mother has naturally occurring A and B antibodies. If the baby is type A, B or AB then it is possible for the mom’s antibodies to attach to the baby’s cells resulting in rupturing of the cells and the release of bilirubin. Bilirubin is another of the postpartum lab tests run on babies prior to being released from the hospital to go home.

Other Testing

Every baby must also have a PKU test which tests for the presence of the enzyme to break down phenylalanine. If this enzyme is missing then the child’s diet will need to be monitored to prevent phenylalanine from building up in the bloodstream. Other tests done in conjunction with the PKU include tests for hypothyroidism and galactosemia. Depending on the laws governing the state the baby is born in there may be a number of other tests done for potential metabolic disorders.