Disappearance curves of serum βhCG in three groups of women. Semilogarithmic scale. Upper curve represents women (n=36) who had elective
vacuum aspiration abortion at 7-13 weeks LMP. Middle curve represents
women (n=35) with spontaneous abortion at 6-15 weeks LMP treated with
uterine aspiration. Lower curve represents women (n=35) with ectopic pregnancies
diagnosed 2.5-11.0 weeks after LMP and removed surgically.
Source: Steier et al. (1984) with permission.
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The initial decrease in beta hCG (βhCG) after full-term delivery is quite rapid, so that an hCG level following the delivery will have dropped to less than 50 mIU within 2 weeks, and hCG will be undetectable after 3 to 4 weeks.12 In the case of first-trimester abortion, if hCG is clearing normally from the bloodstream as expected, the hCG level should decline steadily, halving at least every 48 hours. However, initial hCG levels are at the peak at 8 to 10 weeks LMP, as high as 150,000 mIU; therefore even 2 weeks after first-trimester abortion, the hCG levels may still be 1,500 mIU, high enough that all pregnancy tests will still be positive. hCG is likely to be detectable by sensitive tests, including commonly-used office urine test kits, for as long as 60 days after first-trimester abortion.
When patients have medication abortion, beta hCG continues to increase following mifepristone but then declines precipitously after administration of misoprostol.By the first follow-up visit 5-17 days after taking mifepristone, beta hCG levels drop to 20% of the initial value (measured on the day of mifepristone) in 98.5% of successful medication abortions. In contrast to the usual pattern of sharp drop in hCG after medication abortion, it is possible for hCG levels to have a lengthy plateau even though the patient has a clinically normal course without need for surgical intervention. Patients who require surgical intervention less than 15 days after medical abortion due to prolonged bleeding or pain generally have higher absolute and relative beta hCG values than women with normal courses whose beta hCG values drop sharply.However, there is an overlap in absolute and relative beta hCG values between patients with lengthy plateau who in the end have successful medication abortion and those who will require uterine aspiration. Beta hCG measurement is merely a supplement to the general clinical evaluation in determining whether intervention is indicated.
If intrauterine pregnancy continues to evolve after medication or surgical abortion, an upward trend (mean 124% rise, minimum 53% rise in 2 days) will be seen in serial quantitative beta hCG values. If an ectopic pregnancy continues to evolve after medication or surgical abortion, beta hCG values can behave erratically; these patterns are discussed in more detail in the section, Managing Problems in Early Pregnancy.
Hormone Structure and Pregnancy Test Design
hCG is closely related in molecular structure to the pituitary hormones LH (luteinizing hormone), FSH (follicle stimulating hormone), and TSH (thyroid stimulating hormone). Each is composed of an alpha and a beta subunit. The alpha subunits of LH, FSH, TSH, and hCG are virtually identical, but the beta subunits are unique. Therefore, only a test that selectively identifies the beta subunit of hCG or its unique molecular conformation is specific for hCG.
Highly sensitive urine pregnancy tests commonly used for office or home tests are specific for hCG, and so is the quantitative serum hCG determination in the laboratory. Less sensitive urine pregnancy tests, however, detect whole molecule hCG rather than the beta subunit and therefore show at least some cross-reactivity with LH since their beta units are almost identical.
Sensitive urine pregnancy tests are not useful at the follow-up visit to confirm that the abortion was successful, because hCG may not clear from the body for a month or more following complete abortion.
A serum pregnancy test is logical only when serial, quantitative hCG levels are needed to monitor a possible ectopic pregnancy or to evaluate a missed or incomplete spontaneous abortion. For confirming pregnancy, a urine pregnancy test performed in a clinical setting is simple, inexpensive, fast (results are available immediately), and has high accuracy.
Continuing pregnancy. In rare cases, an attempt to terminate pregnancy fails altogether (about 0.03% to 0.05% of aspiration proceduresand 0.2% to 1% of early medication abortions).A woman with a continuing pregnancy may have ongoing symptoms of pregnancy and a soft or enlarged uterus. Ultrasound or a low-sensitivity pregnancy test may help to identify this problem (see Pregnancy Testing and Management of Early Pregnancy, Chapter 23). Providing or referring the patient for an effective means to terminate the pregnancy is appropriate treatment.
Meticulous tissue examination after an aspiration abortion minimizes the risk of a continuing pregnancy. Failure to visualize products of conception in the aspirate warrants further investigation for a continuing intrauterine pregnancy or an ectopic pregnancy.Failed aspiration abortion occurs more often in women with uterine abnormalities, such as a bicornuate uterus or cavity distorted by fibroids. Treatment options include medication abortion (if the patient is still within an eligible gestational age limit) or respiration using ultrasound guidance as needed.Ongoing pregnancy due to failed medication abortion potentially involves an increased risk for fetal malformation, so the woman should be encouraged to consider carefully before deciding to continue the pregnancy to term.
FOLLOWING MEDICAL ABORTION....
Methods used to confirm abortion include a history of bleeding with evidence of uterine involution on follow-up examination, appropriately falling serum quantitative hCG determinations, or ultrasonography.Although most medication abortion researchers in the United States relied on ultrasonography to assess gestational age and clinical outcomes, providers in many countries offer safe medication abortion services without routine use of ultrasound.Whatever method you choose to follow patients, remember these important guidelines:
- If a woman has a gestational sac on initial ultrasound examination and no sac on follow-up, then her abortion is complete.Aspiration for "debris" in the uterus in not indicated unless the patient is bleeding heavily or has symptoms or signs of infection.
- If you are following serum hCGs in a woman who did not have an intrauterine pregnancy confirmed by pre-abortion ultrasound, draw an initial quantitative hCG test on the day of mifepristone or methotrexate administration and a second test about 24 to 72 hours after she uses misoprostol (no later than 1 week following the start of treatment). If the hCG values fall by at least 50%, the abortion is most likely complete.Rapidly rising hCG values usually signal a continuing pregnancy, while a slow rise, plateau, or slow fall may indicate ectopic pregnancy (see Pregnancy Testing and Management of Early Pregnancy, Chapter 23)
- Absent or minimal bleeding after taking misoprostol is a warning sign for possible ectopic pregnancy, unless pre-abortion ultrasonography showed a definitive intrauterine pregnancy.
- Sensitive urine pregnancy tests are not useful at the follow-up visit to confirm that the abortion was successful, because hCG may not clear from the body for a month or more following complete abortion (see Pregnancy Testing and Management of Early Pregnancy, Chapter 23).
Ongoing research seeks to simplify the process of medication abortion.For example, one study evaluated the accuracy of using patient history to predict complete abortion; when both patients and providers agreed that expulsion had occurred, ultrasonography showed that they were correct 99% of the time.If further research confirms these results, home-based assessment of outcome may eventually replace in-person follow-up for many women.
This answer came almost entirely from the 19th edition of Contraceptive Technology, a book that describes how all the contraceptives work, the advantages and disadvantages of each and much more! The chapters are by nationally recognized experts.
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Key Words:abortion, urinary tract infection, positive pregnancy test, blood test, hCG level, terminated, Contraceptive Technology, decrease, uterine aspiration, miscarriage, surgical treatment, ectopic pregnancies, hormone structure
Posted 5-15-2009, Updated 6-1-2009