42. A client, who is 23 years old, gravida 2, para 0, had a miscarriage at 6 weeks' gestation last year. She presents for her first prenatal appointment at 12 weeks' gestation. She is having blood drawn for routine prenatal screening. Which laboratory result would indicate a risk to the fetus for erythroblastosis fetalis?
. Low α-fetoprotein.
. Blood type B–, antibody +.
. Lecithin/sphingomyelin ratio of 2:1.
. Blood type O+, antibody –.
Test-Taking Tip
Remember: if a woman is Rh negative and antibody +, the fetus is at risk for developing Rh incompatibility and possibly erythroblastosis fetalis. Eliminate Answers 1 and 3 because they do not test for erythroblastosis fetalis.
Content Area: Maternity, Antepartum; Integrated Process: Nursing Process, Analysis; Cognitive Level: Application; Client Need/Subneed: Physiological Integrity/Reduction of Risk Potential/Laboratory Values
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Answer 1 is incorrect because α-fetoprotein (AFP) is drawn in the second trimester around 18 weeks' gestation. Low AFP may indicate Down syndrome. Answer 2 is correct because this client has a positive (+) antibody screen indicating antibodies are present. The antibodies formed by a mother can cause erythroblastosis fetalis. Blood and Rh typing and antibody screening can alert the physician to the possible development of this condition. Answer 3 is incorrect because the lecithin/sphingomyelin ratio is obtained from amniotic fluid analysis and indicates fetal lung maturity. This test is not performed in the first trimester of pregnancy. Answer 4 is incorrect because the antibody screen is negative, indicating that the client has not developed antibodies that can cause erythroblastosis fetalis.