Knowledge | Oligohydramnios: A Hidden Risk During Pregnancy
Oligohydramnios means that amniotic fluid is below the normal level and may seriously threaten the unborn baby. It occurs in 4% of full-term pregnancies, rising to 12% when pregnancy continues two weeks past the due date.
What is oligohydramnios?
Amniotic fluid is a vital protective environment during pregnancy. It provides room for fetal movement, supports normal limb development, and promotes development of the lungs, gastrointestinal tract, and kidneys. Amniotic fluid begins forming after about 12 weeks of pregnancy and gradually increases, peaking at 36 weeks. It then remains stable for a month before gradually declining. Normal total volume is about half a quart to one quart.
Severity varies by stage of pregnancy. Some cases are mild, with levels only slightly below normal, while others are severe and may cause serious complications.
Causes of oligohydramnios
Causes vary. Some are isolated events, while others are associated with congenital or genetic conditions. The cause is unknown in about 50% of cases, termed idiopathic oligohydramnios.
After 14 weeks, nearly all amniotic fluid consists of fetal urine, so any condition affecting urine output can reduce fluid. Common causes include:
Post-term pregnancy: Amniotic fluid normally declines but may still create problems.
Premature rupture of membranes: Membrane rupture causes fluid leakage in about 37% of second- or third-trimester cases.
Placental abruption: The placenta separates from the uterine lining in about 8.6% of cases.
Fetal birth defects: These commonly involve abnormal kidney or urinary tract development.
Chromosomal abnormalities: About 10% of second-trimester cases involve chromosomal abnormalities.
Twin-to-twin transfusion syndrome: In twins sharing a placenta, one has too little fluid and the other too much.
Maternal diabetes and hypertension: Both are associated with low amniotic fluid.
Diagnosis
Oligohydramnios is usually diagnosed by ultrasound. During routine prenatal care, a sonographer may identify low fluid and investigate further. Ultrasound uses sound waves to measure fluid and assess whether the membranes have ruptured or are leaking.
After an initial finding, the doctor may perform a pelvic examination to determine whether the amniotic sac is damaged and investigate the cause.
Symptoms
Most pregnant women do not feel symptoms themselves, but certain signs may concern a doctor:
Vaginal fluid leakage
Uterus smaller than expected for gestational age
Perceived reduction in fetal movement
Marked reduction in movement compared with the previous pattern
Complications
Severity depends on timing; earlier onset generally causes more serious complications. With second-trimester oligohydramnios, fetal survival is only 10.2%, compared with 85.3% in the third trimester.
Possible complications of early oligohydramnios include:
Preterm birth
Miscarriage
Stillbirth
Limb and facial development problems caused by increased intrauterine pressure
Infection following membrane rupture
Third-trimester complications may include:
Umbilical cord compression that interrupts fetal nutrient supply
Fetal growth restriction
Impaired fetal lung development and breathing problems
Higher risk of cesarean delivery
Risk of preterm birth
Treatment
Treatment depends on fluid level and gestational stage. Options include:
Frequent ultrasound: Regular monitoring of fluid levels and fetal development.
Specialized ultrasound: Doppler ultrasound can assess the placenta, particularly with fetal growth restriction.
Hydration: Research suggests adequate maternal hydration helps maintain normal fluid levels.
Control of maternal conditions: Diabetes or hypertension must be managed.
Fetal intervention: A urinary tract obstruction may require intervention.
Medication: May help prepare the fetal lungs for preterm birth.
Early delivery: Sometimes considered to protect the baby's health.
Management during delivery
When oligohydramnios is diagnosed, delivery in a medical facility is recommended so staff can promptly manage complications during and after birth. Management is individualized and may include identifying the cause in advance or providing necessary fetal treatment during labor.
Knowledge | Oligohydramnios: A Hidden Risk During Pregnancy
Knowledge | Oligohydramnios: A Hidden Risk During Pregnancy
Oligohydramnios means that amniotic fluid is below the normal level and may seriously threaten the unborn baby. It occurs in 4% of full-term pregnancies, rising to 12% when pregnancy continues two weeks past the due date.
What is oligohydramnios?
Amniotic fluid is a vital protective environment during pregnancy. It provides room for fetal movement, supports normal limb development, and promotes development of the lungs, gastrointestinal tract, and kidneys. Amniotic fluid begins forming after about 12 weeks of pregnancy and gradually increases, peaking at 36 weeks. It then remains stable for a month before gradually declining. Normal total volume is about half a quart to one quart.
Severity varies by stage of pregnancy. Some cases are mild, with levels only slightly below normal, while others are severe and may cause serious complications.
Causes of oligohydramnios
Causes vary. Some are isolated events, while others are associated with congenital or genetic conditions. The cause is unknown in about 50% of cases, termed idiopathic oligohydramnios.
After 14 weeks, nearly all amniotic fluid consists of fetal urine, so any condition affecting urine output can reduce fluid. Common causes include:
Post-term pregnancy: Amniotic fluid normally declines but may still create problems.
Premature rupture of membranes: Membrane rupture causes fluid leakage in about 37% of second- or third-trimester cases.
Placental abruption: The placenta separates from the uterine lining in about 8.6% of cases.
Fetal birth defects: These commonly involve abnormal kidney or urinary tract development.
Chromosomal abnormalities: About 10% of second-trimester cases involve chromosomal abnormalities.
Twin-to-twin transfusion syndrome: In twins sharing a placenta, one has too little fluid and the other too much.
Maternal diabetes and hypertension: Both are associated with low amniotic fluid.
Diagnosis
Oligohydramnios is usually diagnosed by ultrasound. During routine prenatal care, a sonographer may identify low fluid and investigate further. Ultrasound uses sound waves to measure fluid and assess whether the membranes have ruptured or are leaking.
After an initial finding, the doctor may perform a pelvic examination to determine whether the amniotic sac is damaged and investigate the cause.
Symptoms
Most pregnant women do not feel symptoms themselves, but certain signs may concern a doctor:
Vaginal fluid leakage
Uterus smaller than expected for gestational age
Perceived reduction in fetal movement
Marked reduction in movement compared with the previous pattern
Complications
Severity depends on timing; earlier onset generally causes more serious complications. With second-trimester oligohydramnios, fetal survival is only 10.2%, compared with 85.3% in the third trimester.
Possible complications of early oligohydramnios include:
Preterm birth
Miscarriage
Stillbirth
Limb and facial development problems caused by increased intrauterine pressure
Infection following membrane rupture
Third-trimester complications may include:
Umbilical cord compression that interrupts fetal nutrient supply
Fetal growth restriction
Impaired fetal lung development and breathing problems
Higher risk of cesarean delivery
Risk of preterm birth
Treatment
Treatment depends on fluid level and gestational stage. Options include:
Frequent ultrasound: Regular monitoring of fluid levels and fetal development.
Specialized ultrasound: Doppler ultrasound can assess the placenta, particularly with fetal growth restriction.
Hydration: Research suggests adequate maternal hydration helps maintain normal fluid levels.
Control of maternal conditions: Diabetes or hypertension must be managed.
Fetal intervention: A urinary tract obstruction may require intervention.
Medication: May help prepare the fetal lungs for preterm birth.
Early delivery: Sometimes considered to protect the baby's health.
Management during delivery
When oligohydramnios is diagnosed, delivery in a medical facility is recommended so staff can promptly manage complications during and after birth. Management is individualized and may include identifying the cause in advance or providing necessary fetal treatment during labor.
When to seek medical care
Contact a doctor or midwife immediately for:
Vaginal fluid leakage
Vaginal bleeding
Uterine contractions
Abdominal or pelvic pain
Reduced fetal movement
Story source:
Collected online