Answer from:
Early OHSS that is because HCG triggers and as long as they don’t proceed on to an embryo transfer, those should have hopefully resolved in a week normally. The problem with late OHSS is because that’s been driven by the pregnancy HCG and then for the pregnancy hormones and that has a much longer course potentially – lasting right through the first trimester. Because it’s going and then you get a reduction in the HCG levels at the end of the first trimester. You can have been quite ill for several months with that and that’s why for example, using luma liquid heparin to reduce the risk of deep thrombosis will often carry that all the way through the first trimester pregnancy and just to make sure of reducing that risk.
