Multifocal osteonecrosis is defined by the involvement of 3 or more anatomic sites. It is unusually observed in only 3–11% of patients with osteonecrosis. The most common sites affected are the femoral head, knee, and humeral head respectively .
Main rheumatologic diseases associated with MFON are SLE, IBD, secondary APLS, Sjogren syndrome, systemic sclerosis, and Behcet. It is not common in primary antiphospholipid .
Hip pain during the later stages of pregnancy and during the postpartum period is a common presentation and usually misdiagnosed as sciatica, pelvic structural compression, and lumbosacral strain . Transient osteoporosis, which is self-limiting and typically resolves within months, and osteonecrosis, which results in femoral head collapse and degenerative changes in the joint, can also cause pain .
The etiology of osteonecrosis of the femoral head during pregnancy is still largely unknown. However, theories have been proposed suggesting the pathogenesis is likely to be multifactorial including hormonal, mechanical, and coagulation factors . Venous congestion and hypercoagulability are common in the third trimester during pregnancy. Other possible etiologies are ovarian hyperstimulation drugs, which have the detrimental effects of hyperviscosity and hypercoagulability, and the mechanical stress or overload by excessive labor and weight gain during the last trimester of pregnancy . There are many endocrine modifications that occur during pregnancy as parathyroid hyperplasia and the excess production of estrogen and progesterone by the placenta  leading to destabilization of endogenous plasma lipoproteins and lipid metabolism in the liver, which could promote fat embolism. Also, an increase in estrogen and progesterone results in increased adrenocortical activity and levels of adrenal corticosteroids to almost three times the level of a non-pregnant woman .
Hormonal/ drug-induced osteonecrosis includes steroid-induced osteonecrosis. Zhang et al.  reviewed 43 cases of steroid-induced osteonecrosis following the SARS epidemic and suggested that a single dose of 200 mg of methylprednisone or a cumulative dose of more than 4000 mg was a significant risk factor for the development of multifocal osteonecrosis. Gunal and Karatosun  showed bilateral osteonecrosis of the hip after a single dose (75.5 mg) for treatment of an allergic reaction. Mckee et al.  reviewed 15 cases of osteonecrosis with a mean of 20.5 days of treatment and doses of up to 3300 mg of prednisone.
There had been a similar case but in a male patient published before: osteonecrosis and antiphospholipid in 2009 .