PCR - polymerase chain reaction. A procedure that produces millions of copies of a short segment of DNA; the amplified product, doubled each cycle for 30 more cycles, can then be subjected to further testing; it is a common procedure in molecular genetic testing in order to generate enough DNA to perform the test; in individuals suspected of having myotonic dystrophy, it can be used to determine the number of trinucleptide repeats in the DMPK gene on the 19th chromosome.

PGD. Abbreviation for preimplantation genetic diagnosis achieved through in vitro fertilization where analysis of embryos is done prior to being implanted by a doctor into the uterus of a woman.

Pacemaker. An implanted heart device to correct a very slow or irregular heart beat.

Pathogenesis. Biological mechanism that leads to a diseased state.

Perioperative. Around the time of surgery.

Pharynx. The upper expanded portion of the digestive tube, between the esophagus below the mouth and nasal cavities above and in front.

Phenotype. The observable signs, symptoms and other aspects of a person's outward appearance and behavior.

PICU. Pediatric intensive care unit.

Pilomatrixoma. Benign skin tumors under the skin; associated with hair follicles.

Placenta. Organ formed inside the lining of the womb that provides nourishment for fetus and elimination of its waste products.

Placenta accreta. Condition in pregnancy in which the placenta (see definition) has an abnormally deep attachment through the endometrium and into the myometrium (the middle layer of the uterine wall), causing full or partial placental retention. Condition typically requires surgery to prevent abnormal post-partum bleeding and fully remove the placenta. In severe cases can lead to a hysterectomy or can be fatal. 

Placenta previa. Condition in pregnancy in which the placenta (see definition) is implanted in lower segment of womb close to the internal opening of the cervix, or sometimes completely covering that internal opening.

Polyhydramnios. Excessive amniotic fluid build-up during pregnancy.

Postoperative apnea. Absence of breathing after surgery.

Postpartum hemorrhage. Heavy bleeding from the birth canal after vaginal delivery of a baby.

Preferred Provider Organization (PPO). A type of health plan where you pay less if you use providers in the plan’s network. You can use doctors, hospitals, and providers outside the network without a referral for an additional cost.

Preimplantation genetic diagnosis (PGD). A form of genetic testing that analyzes and examines embryos during in vitro fertilization (IVF) before fertilized eggs are transferred back to the uterus in order to determine if the embryo has certain genetic conditions.

Premium. The amount you pay for your health insurance every month. In addition to your premium, you often must pay other costs for your healthcare, including a deductible, copayments, and coinsurance.

Pre-mutation. The presence of slightly more than the normal number of nucleotide repeats in the genetic mutation, e.g. in DM1, somewhere between 38 and 50; CTG repeats; the person exhibits no symptoms but are at risk of having affected children.

Prenatal diagnosis. A process of determining whether a child in the womb has a specific inherited disorder.

Prevalence. Counting exiting disease diagnosis in a single point in time.

Prognosis. Forecast of the probable course and outcome of a disease.

PROMM. Abbreviation for proximal myotonic myopathy or DM2.

Proximal. In medicine, it refers to a part of the body that is nearest to the trunk of the body, such as thighs and upper arms.

Ptosis. Droopy eye-lids due to muscle atrophy.

Pulse oximetry. A test to measure oxygen levels in the blood.