A woman at 39 weeks gestation suddenly develops vaginal bleeding and the fetal rate drops to 80 beats/min, and is non reassuring.
What should you do?
Correct Answer C:
Vasa previa is an obstetric complication defined as "fetal vessels crossing or running in close proximity to the inner cervical os. These vessels course within the membranes (unsupported by the umbilical cord or placental tissue) and are at risk of rupture when the supporting membranes rupture."
Vasa previa is present when fetal vessels traverse the fetal membranes over the internal cervical os. These vessels may be torn at the time of labor, delivery or when the membranes rupture. It has a high fetal mortality because of the bleeding that follows.
The classic triad are membrane rupture followed immediately by painless vaginal bleeding and fetal bradycardia.
The diagnosis is usually confirmed after delivery on examination of the placenta and fetal membranes. Treatment immediately with an emergency cesarean delivery is usually indicated.
A 34-year-old female G7P5A1 in the 30th week of gestation presents with complaints of vaginal bleeding. She noticed the bleeding while at home and was not involved in any strenuous activity or trauma. She denies any pain. She denies alcohol or drug use. She underwent both vaginal and C-section delivery (first 3 children and her last 2 children respectively).
Her BP is 120/70 mmHg; HR is 80/min; T is 37.2°C; RR is 15/min, the blood loss seems to be minimal. The Apt test is positive.
Which of the following is least likely to be a risk factor of this condition?
Correct Answer A: The most likely diagnosis is Vasa previa. This is suggested by painless vaginal bleeding in the third trimester, her obstetrical history, and the Apt test which is positive. The Apt test is used to differentiate between fetal blood and maternal blood. It is positive in Vasa previa. In practice since Vasa previa is an emergency, it is better to confirm it with readily available imaging studies that could give faster results such as ultrasound or color flow Doppler.
Vasa previa refers to fetal vessels running through the membranes over the cervix and under the fetal presenting part, unprotected by placenta or umbilical cord. The condition usually results either from a velamentous insertion of the cord into the membranes rather than the placenta or from vessels running between lobes of a placenta with one or more accessory lobes. Common risk factors for Vasa previa are multiple pregnancies, bilobed placenta, velamentous cord insertion, in vitro fertilization, low-lying placenta or placenta previa, uterine surgery, and succenturiate-lobed placenta. Therefore, a high positioned placenta (choice A) is the least likely cause of Vasa Previa among the choices given.
→ Velamentous cord insertion (choice B), Bi-lobed placenta (choice C), Multiple pregnancies (choice D), In vitro fertilization (choice E) are all common risk factors of Vasa previa.
Key point:
Vasa previa is characterized by painless vaginal bleeding and may present in second or third trimester. It constitutes loss of fetal blood and as such it is an emergency. The Apt test can be used to differentiate fetal blood from maternal blood.
A female patient is a newcomer to the country. She is single and in labor. She has had no prenatal care.
You decide to give her anti-Rh Ig (RhoGam) to prevent which one of the following in subsequent pregnancies?
Hemolytic disease of the newborn (also called erythroblastosis fetalis) is a condition in which red blood cells are broken down or destroyed more rapidly than is normal. The newborn's red blood cells are destroyed by antibodies that were produced by the mother and crossed the placenta from the mother's circulation into the fetal circulation before delivery. A mother who is Rh-negative may have produced antibodies against Rh-positive blood cells after she was exposed to red blood cells of a previous fetus that was Rh-positive. Such exposure may occur during pregnancy or labor, but may also occur if the mother had been accidentally transfused with Rh-positive blood at any time earlier in life.
The mother's body responds to the “incompatible blood” by producing antibodies to destroy the “foreign” Rh-positive cells. These antibodies cross the placenta during a subsequent pregnancy. If the fetus she is carrying is Rh-negative, there is no consequence. However, if the fetus has Rh-positive red blood cells, the mother's antibodies attach to, and start to destroy, the fetal red blood cells, leading to anemia of varying degrees. This anemia begins in the fetus and continues after delivery.
Prevention of hemolytic disease due to Rh incompatibility involves injecting the mother with a Rh0(D) immune globulin preparation at about 28 weeks of pregnancy and again immediately after delivery. Injection of this immune globulin rapidly destroys any Rh-positive fetal red blood cells that have entered the mother's circulation before they stimulate the mother's body to produce antibodies.
In a patient whose blood type is O-Rh negative and whose husband has O-Rh positive blood, Rh immune globulin (RhoGam) should be given in all the following cases, except:
Correct Answer A:
If the father of the baby or donor is Rh positive or unknown, the RH negative patient is a candidate for RhoGAM prophylaxis in the following cases:
What is the diagnostic test used to confirm a diagnosis of Down's syndrome in the fetus of a pregnant woman at 14 weeks gestation?
Correct Answer B:
Amniocentesis, routinely performed at 14-16 weeks’ gestation, remains the criterion standard of invasive diagnostic tests. Testing for chromosomal disorders is 99.5% accurate. Amniocentesis is a procedure used to collect amniotic fluid, the liquid that is in the womb. A needle is inserted through the mother's abdominal wall into the uterus, using ultrasound to guide the needle. This fluid contains fetal cells that can be examined for chromosome tests. Amniocentesis is usually carried out between the 14th and 18th week of pregnancy.
The triple screen test is a maternal blood screening test that looks for three specific substances: AFP, hCG, and Estriol. The triple screen test is performed between the 15th and 20th week of pregnancy although results obtained in the 16th - 18th week are said to be the most accurate.
Low values for AFP and Estriol and high values for hCG are seen in Down's Syndrome. Low levels of all three seen in trisomy 18. High levels for AFP are seen in neural tube defects like spina bifida.
Ultrasound Screening is used to confirm the gestational age of the fetus (it's more accurate than dating from the mother's last menstrual cycle). Another benefit of the ultrasound can also pick up problems of a serious medical nature, such as blockage of the small intestine or heart defects. Knowing these defects exist as early as possible will benefit the treatment of the child after birth.
Chorionic Villus Sampling (CVS) is a procedure where a small amount of tissue is taken from the young placenta (also called the chorionic layer). These cells contain the fetal chromosomes that can be tested for Down syndrome. CVS is usually carried out between the 10th and 12th weeks of pregnancy. The accuracy of CVS (96-98%) is less than that of midtrimester amniocentesis, because of confined placental mosaicism and maternal-cell contamination.
Click to expand