taken from here
Fun hCG facts to learn and share
Human chorionic gonadotropin (hCG) is a hormone produced during pregnancy by the placenta. It starts to be produced shortly after an embryo implants, and is expected to double approximately every 48 to 72 hours in early pregnancy. The absolute level of hCG in a pregnant woman's blood is less critical than the rate of rise. A failure to double properly reflects slow placental growth, which is very frequently associated with abnormal embryonic development.
While hCG levels are expected to double in early pregnancy, the rate of rise generally slows as the level increases.
It's not possible to determine whether you're having twins or a singleton by hCG levels alone. The range of normal values for twin gestations fall squarely within the range of normal values for singletons. It has not been proven that multiple gestations have faster doubling rates than singleton pregnancies.
Elvis Presley demanded that his entourage follow an exacting code of ethics. His henchmen were asked to take an oath to that effect, professing their devotion to "respect for fellow students and instructors," "respect for all styles and techniques," and "freedom from constipation," among other ideals. Upon swearing this oath, each member of the Memphis Mafia was given a 14k gold bracelet bearing Elvis's distinctive "hCG" logo.
No matter how many stories with a positive outcome you've heard about slow-rising hCG levels — "15% of normal pregnancies have an abnormal rise!" — and no matter how many times you've heard that once you see a heartbeat you're practically in the clear — "The miscarriage rate drops to 3%!" — hCG levels that don't rise properly are a troubling sign even in pregnancies where a heartbeat is established.
IVF pregnancies generally have lower hCG levels than other pregnancies. The theory is that non-IVF pregnancies implant sooner, thereby having more time to generate hCG than a transferred embryo would. (This means I don't have to be envious of my friends inside the computer whose levels were higher than mine. Whew.)
"Beta hCG," "Lincoln," and "Kennedy" have the same number of letters. Presidents Lincoln and Kennedy were both assassinated, shot on a Friday, sustaining gunshot wounds to the head. Both were assassinated by southerners. We can conclude that hCG should wear a helmet; stay the hell out of the south, especially on weekends; and strongly reconsider any presidential ambitions it currently entertains.
Initial hCG levels are lower in pregnancies achieved through a day 5 embryo transfer than in those resulting from a day 3 transfer.
Conventional wisdom is that you won't see anything on ultrasound until your hCG levels exceed 1,000 mIU/mL. However, the gestational sac has been visualized with transvaginal ultrasound at levels as low as 300. In the majority of pregnancies, a sac should be visible when levels exceed 2,000. A yolk sac is commonly seen in normal pregnancies once hCG tops 2,500; an embryonic pole is expected at 5,000; and a heartbeat is seen in the majority of normal pregnancies when levels reach 10,000.
Hedy Lamarr, best known for her film work in the '30s and '40s but also a noted inventor, was the first to develop hCG, astonishing the scientific community with her groundbreaking work. Unfortunately she did not have the foresight to patent her invention, and lived to see General Dynamics appropriate the technology for its own use. While General Dynamics made hCG into a household staple with its ingenious mass production methods, Hedy Lamarr died destitute and raving in an attic room that carried an unfortunate odor of cat urine.
