The etiology of intrapartum or postpartum sacral stress fractures has thus far not been determined. To date, 29 cases of sacral stress fractures in athletes have been described in the literature [2
]. To the best of our knowledge, nine cases of postpartum stress fractures have been described. Of these, only six cases have reported the patient's bone density: five presented with normal and one with decreased bone density [11
]. The incidence of pregnancy-related osteoporosis is approximately 0.4 cases per 100,000 women. Sacral stress fractures present universally with pain localized to the lower back, sacroiliac region, buttocks or groin. Radicular pain is common and described in a number of cases [2
]. A positive Patrick's test or a tender sacroiliac joint is typically found on clinical examination. There are several other tests to localize sacroiliac joint pain that are also useful in the examination of sacral stress fracture (Table , [13
Table 1 Specific pain tests for the iliosacral-region from Dreyfuss et al. 
Imaging is paramount in securing the diagnosis. Concerns regarding radiation exposure to the developing fetus limit the imaging options. Plain radiographs expose the unborn child, and are only utilized for ruling out other sources of pain. Shah and Stewart [2
] reviewed a series of 27 sacral stress fractures and found 25 cases with normal radiographs.
MRI is the modality of choice during pregnancy because of its lack of radiation emissions. As in our patient, all cases described in the literature involved a vertical fracture line with surrounding edema on the MRI scans. If necessary, after delivery, bone scintigraphy or bone scans with higher sensitivity than MRI can be utilized [2
Bone density measurements should be performed to rule out pregnancy-related osteoporosis.
Because of the high radiation load, the investigation should occur only after the pregnancy has ended. For assessment of the bone density during pregnancy, osteosonometry can be considered, but its use is controversial and not evidence-based.
Pregnancy-related osteoporosis most often occurs in the third trimester [14
], and if the bone mineral density does not normalize within five to ten years of the delivery, then the osteoporosis is likely to be permanent [14
]. Along with sacral fractures, vertebral compression fractures as well as osteoporosis of the proximal femur are associated with pregnancy. Therefore these areas should be examined for injuries after a bone density measurement.
The first step in the pain management of sacral stress fractures is usually rest and activity modification [2
]. This is difficult in pregnant patients in whom the stress on the fracture is exerted by the fetus. There is some controversy with those supporting early mobilization because weight bearing appears to be necessary to stimulate osteoblastic activity [6
]. In our case of an intrapartum sacral fracture, pain control was the greater challenge because of the limited therapy options. In such cases, we endorse early immobilization until sufficient pain control is achieved. Subsequent partial weight bearing is essential to accelerate bone healing and to reduce other complications of immobility.
The following points should be considered for the application of analgesics during pregnancy: effects on the fetus, stage of the pregnancy, influence on the pregnancy course, influence on the mother, risk of pre-eclampsia and analgesia. In principle, especially early in pregnancy, there should be strict indications, low dosages and a short duration of drug administration. Oral paracetamol is the primary analgesic choice during all phases of pregnancy. Ibuprofen can also be used under a strict maximum daily dose of 1,600 mg. In certain situations, intravenous Perfalgan (paracetamol), morphine or pethidine can be administered. Because of its less systemic side effects, epidural anesthesia is recommended in cases of severe pain of the lower extremity and sacrum that is refractory to other therapies.
The cases currently described in the literature demonstrate that most patients regain their activities of daily living within six weeks. Surgical treatment was never necessary. The heterogeneity of the risk groups (pregnant women, endurance athletes or older patients) and the differences between stress and insufficiency fractures mean that treatment options must be adapted. Nevertheless, in all cases, a prompt diagnosis and sufficient pain management must be achieved.