An imperforate hymen is a congenital disorder where a hymen without an opening completely obstructs the vagina. It is caused by a failure of the hymen to perforate during fetal development. It is most often diagnosed in adolescent girls when menstrual blood accumulates in the vagina and sometimes also in the uterus. It is treated by surgical incision of the hymen. Signs and symptoms
Affected newborns may present with acute urinary retention. In adolescent females, the most common symptoms of an imperforate hymen are cyclic pelvic pain and amenorrhea; other symptoms associated with hematocolpos include urinary retention, constipation, low back pain, nausea, and diarrhea. Other vaginal anomalies can have similar symptoms to an imperforate hymen. Vaginal atresia and a transverse vaginal septum require differentiation. A strong urge to defecate has been observed in a few women. Complications
If untreated or unrecognized before puberty, an imperforate hymen can lead to peritonitis or endometriosis due to retrograde bleeding. Additionally, it can lead to mucometrocolpos (dilatation of the vaginal canal and uterus due to mucus buildup) or hematometrocolpos (dilatation due to buildup of menstrual fluid). Mucometrocolpos and hematocolpos can in turn cause urinary retention, constipation, and urinary tract infection. Pathophysiology
An imperforate hymen is formed during fetal development when the sinovaginal bulbs fail to canalize with the rest of the vagina. Although some instances of familial occurrence have been reported, the conditions occurrence is mostly sporadic, and no genetic markers or mutations have been linked to its cause.
As per Lu and Nightingale, serum magnesium concentrations associated with maternal toxicity (also neonate depression, hypotonia and low Apgar scores) are:

7.0–10.0 mEq/L – Loss of patellar reflex
10.0-13.0 mEq/L – Respiratory depression
15.0-25.0 mEq/L – Altered atrioventricular conduction and (further) complete heart block
>25.0 mEq/L – Cardiac arrest

Complications
Severe hypermagnesemia (levels greater than 12 mg/dL) can lead to cardiovascular complications (hypotension and arrhythmias) and neurological disorder (confusion and lethargy). Higher values of serum magnesium (exceeding 15 mg/dL) can induce cardiac arrest and coma. Causes
Magnesium status depends on three organs: uptake in the intestine, storage in the bone, and excretion in the kidneys. Hypermagnesemia is therefore often due to problems in these organs, mostly the intestine or kidney. Predisposing conditions
Hemolysis, magnesium concentration in red blood cells is approximately three times greater than in serum, therefore hemolysis can increase plasma magnesium. Hypermagnesemia is expected only in massive hemolysis. Chronic kidney disease, excretion of magnesium becomes impaired when creatinine clearance falls below 30 ml/min. However, hypermagnesemia is not a prominent feature of chronic kidney disease unless magnesium intake is increased. Magnesium toxicity from emergency pre-eclampsia treatment during labor and delivery. Other conditions that can predispose to mild hypermagnesemia are diabetic ketoacidosis, adrenal insufficiency, hypothyroidism, hyperparathyroidism, and lithium intoxication. Metabolism
For a detailed description of magnesium homeostasis and metabolism see hypomagnesemia. Diagnosis
Hypermagnesemia is diagnosed by measuring the concentration of magnesium in the blood. Concentrations of magnesium greater than 1.1 mmol/L are considered diagnostic.