HCG Screening and Multiple Pregnancy
One of the earliest ways to detect the possibility of multiples is by monitoring the level of human chorionic gonadotropin (or HCG) in the mother's body. HCG is a hormone secreted by the fertilized egg(s). It regulates the production of other hormones, such as progesterone and estrogen, until the placenta develops and assumes that role.
Essential
Not every woman is a candidate for HCG monitoring. Many women never have their levels evaluated beyond a urine test to confirm pregnancy. However, some doctors do recommend testing, particularly in situations where there has been conception assistance or a history of miscarriage.
HCG is the substance detected by common over-the-counter pregnancy tests to determine if a woman is pregnant or not. These tests measure the amount of HCG in a urine sample to determine whether there is enough of the hormone to indicate pregnancy.
But HCG monitoring of a blood sample provides a more comprehensive picture of the woman's status. It not only indicates whether an egg is fertilized, but can be used to determine whether the fertilized egg, implanted in the uterus, is developing into an embryo. An HCG blood test can also suggest the presence of more than one embryo.
A single HCG measurement doesn't tell the story. Rather, samples are taken every few days during the early weeks of pregnancy and compared. With each passing day, increasing amounts of the hormone are detectable in the pregnant mother's system. HCG production peaks toward the end of the first trimester, so it is generally monitored only in the first few weeks of pregnancy.
HCG Levels in Single and Twin Pregnancy | ||
Days from LMP* | HCG Range** for Singleton Pregnancy | HCG Range for Multiple Pregnancy |
28 | 9.4-120 | 9.5-120 |
33 | 300-600 | 200-1,800 |
36 | 1,200-1,800 | 2,400-36,000 |
40 | 2,400-4,800 | 8,700-108,000 |
45 | 12,000-60,000 | 72,000-180,000 |
70 | 96,000-144,000 | 348,000-480,000 |
| *LMP is the date of the start of the last menstrual period. **HCG is measured in mIU/mL | ||
As the chart illustrates, HCG measurements are quite inflated when a multiple pregnancy is present. However, they are not considered a completely reliable indicator of twins or more. In most cases, a high HCG reading will only prompt further investigation.
From The Everything Twins, Triplets, and More Book Copyright © 2005, F+W Publications, Inc. Used by permission of Adams Media, an F+W Publications Company. All rights reserved.
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