For a long time, some female comrades after the birth of a stubborn back pain, often called “menstrual disease”, thought to be the “root of the disease” during pregnancy life is not organized. In recent years, with the rapid development of rheumatology specialties, the veil of this type of disease is being lifted, the so-called “moon disease” a significant part of the rheumatology category, the common is ankylosing spondylitis, osteoporosis and dense osteitis. A. Ankylosing spondylitis Ankylosing spondylitis is a group of multi-system inflammatory diseases that mainly invade the spine, peripheral joints and peri-articular joints, the disease often occurs in young and middle-aged men, there is a clear family aggregation, the peak incidence of 20-30 years old. Low back pain is the most common symptom of the disease and is accompanied by stiffness of the low back, which is aggravated by rest and relieved by exercise. Some patients with peripheral joint involvement may have joint swelling and pain, and ophthalmoplegia is the most common extra-articular manifestation, seen in 25-30% of patients. However, when the disease occurs in women, symptoms are often mild or present only as asymptomatic imaging damage, so it is often underdiagnosed. It has also been suggested that pregnancy may further reduce the symptoms in women and that the symptoms become more prominent after delivery, a temporal sequence that often leads patients to mistake the disease for “menstrual disease”. In addition to joint involvement, ankylosing spondylitis can lead to respiratory, cardiovascular, and neurological involvement, while cardiovascular system involvement is relatively frequent, occurring in 2-10% of patients, mainly in the form of cardiac arrhythmias, valvular regurgitation, and abnormal myocardial diastolic function. The majority of patients have a good prognosis after a clear diagnosis and standardized treatment. Therefore, women with postpartum low back pain should consult the rheumatology department as soon as possible to investigate the possibility of the disease. Second, osteoporosis Pregnancy is a very special period, the level of neuroendocrine hormones has changed significantly, coupled with: 1, increased demand for calcium in women during pregnancy, the supply is relatively insufficient. 2, reduced exercise: transport can maintain a certain mechanical stimulation of the bones, stimulating the activity of osteoblasts and increasing the formation of bone. 3, insufficient sunlight exposure: insufficient sunlight exposure can lead to a decrease in the synthesis of vitamin D in the skin and a decrease in the utilization of calcium absorption. The above factors determine the incidence of osteoporosis in women during pregnancy is significantly higher than that in the general population. Pain is the most common symptom of osteoporosis, with low back pain being the most common. Pain decreases when lying on the back or sitting, intensifies when stretched back when standing upright or standing or sitting for a long time, and worsens when bending, coughing and straining to stool. After the onset of osteoporosis in women, the disease is unconscious at first, and with the beginning of breastfeeding after delivery, calcium will be further lost; in addition, the weight-bearing movement of carrying the baby and the gradual increase of the baby’s weight will induce compression fractures in the lumbar spine, leading to increased pain, and in severe cases, sensory-motor impairment of both lower limbs, or affecting bladder and rectal functions. The disease is also one of the diseases that are often called “menstrual diseases”. Timely diagnosis and treatment can not only ensure the normal calcium and bone density of the pregnant woman herself, but also largely ensure the calcium intake of the baby and reduce the incidence of rickets in infants and children. The cause of this disease is unknown and may be related to pregnancy, mechanical injury and inflammation. It manifests as lumbosacral pain, lumbar pain, and occasionally radiating pain toward the buttocks in the lower buttocks and posterior thighs. Sclerotic changes in the iliac cortex near the articular surface with dense bone, located in the lower 1/2 of the sacroiliac joint and mostly triangular in shape, are seen on X-ray or CT; the sacroiliac joint gap is neat and clear, with no signs of destruction of the articular surface and bone, and is more common unilaterally. The disease has a good prognosis and should be positively differentiated from ankylosing spondylitis and osteoporosis because the direction and intensity of treatment are very different. Specialized specialist visits help to clarify the diagnosis and avoid misdiagnosis, underdiagnosis and overtreatment. Rheumatology is one of the rising stars in internal medicine, and is also known as the “orthopedic medicine”, which is the best at treating these diseases. Therefore, for women who are planning to get pregnant, pregnant, or after giving birth, regardless of whether they have “low back pain” or not, they should be subconsciously prepared with the above common sense, so that they can truly be “prepared”.