Congratulations! You passed all of your first trimester tests with flying colors ‑- or if not, you and your doctor are working together to take all necessary precautions. Now that you're entering your second trimester, testing won't be such a large part of your scheduled prenatal care. You'll still have a few things to be screened for, though, so here's what you can expect as part of your second trimester testing.
Urine Analysis and Culture
Your health care provider should have taken a urine sample during your initial prenatal visit, way back at the beginning of your first trimester. If you're like most women, you won't need urine analysis or culture again until the third trimester. Women with a history of repeated urinary tract infection, kidney disease, diabetes ‑- gestational or otherwise ‑- or preeclampsia would likely be asked for a urine sample at each prenatal visit. The same holds true for a mother who admits to or is suspected of using street drugs.
As always, urine analysis and culture alert your health care provider to any bacterial infections that might be developing. Your care provider may prescribe antibiotics based on test results.
One or more hemoglobin or hematocrit tests will be done to measure your iron levels. You already know that your iron level can be affected by nutritional deficits, by absorption disorders such as anemia or by blood loss. But you may not have known that your body would be experiencing the "physiologic anemia of pregnancy" during your second trimester. This normally occurs mid-pregnancy as your maternal plasma volume begins to increase more rapidly than your red blood cells can. Simply put, your blood is more dilute at this time. At this stage of pregnancy, anemia is defined as a hemoglobin concentration less than 10.5 g/dL (hematocrit 31%), which is slightly lower than the accepted first and third trimester levels.
Quad or Triple Screen
Between 15 and 21 weeks, another maternal blood test is offered to screen for an elevated risk of carrying a fetus with Down syndrome, trisomy18 or an open neural tube defect. The lab reports the finding in terms of risk and assigns a ratio of probability based on the levels of four makers (quad screen) found within the maternal blood. Data such as mother's weight, race and diabetic status are also figured into the analysis. If results show that the mother's risk is higher than indicated by her age alone, a recommendation is made for further testing, such as a specialized ultrasound or amniocentesis.
Because the indicators for each marker change from week to week, inaccurate dating of the pregnancy often results in abnormal test results. Read: You get a test result that shows abnormalities when there really are none, because your due date has been miscalculated. This test is optional, but your health care provider should discuss it with you and your partner and make sure you have all the information you need to understand your risk factors and make an informed choice about this prenatal testing.
If you've only planned one ultrasound during your pregnancy, it will most likely take place at 18 to 20 weeks. At this point, fetal organ development is well established, and dates can be ascertained with much accuracy, so your due date ‑- and your baby's gestational age ‑- can be adjusted if necessary.