Pregnant women have a hormone during pregnancy which is detected in their blood or urine. This hormone is called a Human Chronic Gonadotropin Hormone ( HCG). The smallest levels of HCH in the blood or urine is enough for a positive result of pregnancy which is detectable within 7 to 8 days after ovulation and the levels doubles every 72 hours for early pregnancy and then, after every three days. However, the hcg levels for twins are different from that of a woman carrying one child. These levels vary depending on the person and the stage at which test is conducted.
Measurement of HCG in pregnancy
HCG is measured in Milli-international units of HCG hormone per milliliter of blood with the SI Unit Miu/ml. A positive pregnancy ought to give a reading of 25 Miu/ml and if it records a level of less than five mIU/ml, the result is considered negative. There are two types of tests conducted to check HCG levels; a qualitative HCG and a quantitative HCG. The former test only confirms whether a woman is pregnant or not while the latter test measures the exact amount of HCG in the blood.
HCG Levels in twins
How different are the HCG levels for women carrying twins and women carrying a single baby? The HCG levels of the former are higher. After missing the first periods, one can have a proper evaluation of the HCG Levels, and at that point, a woman who carries twins will often record levels between 30% and 35 % higher than those with singleton pregnancies.
Using a standard 28 days cycle of tow weeks post ovulation or 14 days past ovulation, women with singleton pregnancies will register low levels of up to 9 miu/l while women with twins will register levels of 17 miu/ml
The HCG levels after four weeks for a woman with twins have been reported to be up to 5 times higher than those of a singleton pregnancy within the same period. The average values for the same period are 129 Miu/ml for singleton and 235 Miu/ml for twins. If the HCG levels at four weeks are higher than 8000 miu/ml or 5 times greater than any of your previous singleton pregnancy, then its likely that you are having twins.
At five weeks, LMP, The lowest HCG levels recorded have been 61 miu/ml for a singleton pregnancy and 106 miu/ml for a woman carrying twins. Over the same period, the highest HCG levels recorded are 19726 miu/ml and 20956 miu/ml for a singleton and twins respectively and-and an average of 1721 miu/ml and 3446 miu/ml for singleton and twins respectively.
At six weeks of pregnancy, women with a singleton pregnancy can record levels as low as 245 miu/ml and as high as 81000 miu/ml whereas women with twins can record lows of 373 miu/ml and highs of 23323 miu/ml. The same expectations are likely to reoccur up to the 10th week.