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Oligohydramnios: Causes, Diagnosis, Management, and Potential Complications

Oligohydramnios: Causes, Diagnosis, Management, and Potential Complications

An Overview

Oligohydramnios is a condition marked by an insufficient amount of amniotic fluid, a crucial protective and nourishing substance surrounding the developing fetus within the womb. In India, where maternal and fetal health remains critical public health priorities, the prevalence and implications of oligohydramnios have garnered increased attention. This article aims to provide a comprehensive understanding of oligohydramnios, covering its diagnosis, underlying causes, management strategies, and potential complications it may pose.

An Overview

Oligohydramnios is a condition marked by an insufficient amount of amniotic fluid, a crucial protective and nourishing substance surrounding the developing fetus within the womb. In India, where maternal and fetal health remains critical public health priorities, the prevalence and implications of oligohydramnios have garnered increased attention. This article aims to provide a comprehensive understanding of oligohydramnios, covering its diagnosis, underlying causes, management strategies, and potential complications it may pose.

Did You Know?

Oligohydramnios is observed in approximately 1-5% of full-term pregnancies Globally. Nevertheless, its prevalence escalates to over 12% in Post Term Pregnancies. Oligohydramnios contributes to approximately 6.5% of all Stillbirths in Low and Middle-income Nations.

What Is Amniotic Fluid?

During pregnancy, the liquid enveloping the fetus inside the uterus is referred to as amniotic fluid. Its essential functions include:

 

  • Facilitating Development: Amniotic fluid supports the proper growth of the fetus’s muscles, bones, organs, lungs, and digestive system. It also contributes to maintaining their temperature and safeguarding the baby.
  • Lung Maturity: The fluid is vital for the maturation of the fetal lungs.
  • Fetal Movement: Enabled by the cushioning effect of the fluid, the fetus moves and changes positions within the womb. This fluid aids in rotation and ensures a cushioning effect, protecting the fetus from external impacts.
  • Umbilical Cord Protection: The amniotic fluid serves to prevent compression of the umbilical cord, which is the connection between the baby and the uterine wall. This safeguarding mechanism is crucial for the baby’s well-being.
 

Amniotic Fluid Volume Throughout Pregnancy:

The production of amniotic fluid begins shortly after conception, around 12 days after fertilization, when the amniotic sac starts forming. Maternal plasma primarily composes the fluid initially. Around 20 weeks of gestation, the fetus’s urine becomes a primary source of the amniotic fluid. This is why the quantity of amniotic fluid reflects fetal urine production, providing insight into the proper development of the baby. Throughout the various stages of pregnancy, the volume of amniotic fluid undergoes changes influenced by different sources:

 

  • In the first trimester, amniotic fluid primarily consists of fetal lung secretions, maternal plasma crossing fetal membranes, and contributions from the placental surface.
  • The second-trimester witnesses a shift as fetal kidneys become the primary source, producing urine that significantly contributes to the amniotic fluid volume.

Amniotic Fluid Levels: 

Amniotic Fluid increases until about 36 weeks, then decreases significantly after 40 weeks. At around 34 weeks, the volume is approximately 800 Milliliters, and by 40 weeks, it is around 600 Millilitres. If the Amniotic Fluid Volume is less than 500 Milliliters between 32-36 weeks of Gestation, it is referred to as Oligohydramnios.

Symptoms of Oligohydramnios

Oligohydramnios symptoms often go unnoticed by pregnant women, but doctors may suspect it if:

 

  • Fluid leaks from the vagina continuously.
  • The uterus is smaller or not growing as expected.
  • Fetal movements are reduced.
  • Maternal weight gain is insufficient. 

A history of low amniotic fluid in a previous pregnancy raises the risk of developing Oligohydramnios in subsequent pregnancies.

 

Causes of Oligohydramnios

Oligohydramnios can arise due to factors involving the fetus, placenta, or mother. Given that amniotic fluid is mainly fetal urine, low volume (oligohydramnios) usually suggests reduced fetal urine or leakage of amniotic fluid from the uterus.

Fetal Factors:

  • Chromosomal abnormalities, including Down Syndrome.
  • Fetal renal conditions such as agenesis, cystic renal diseases, and posterior urethral valves.
  • Events such as intrauterine death, post-term pregnancy, or early rupture of membranes.
  • Intrauterine Growth Restriction (IUGR) and amnion nodosum.

Placental Factors:

  • Conditions like placental abruption, thrombosis, or infarction.
  • Stuck twin syndrome, leading to diminished amniotic fluid in one fetus.

Maternal Factors:

  • Reduced blood supply to the placenta due to conditions like preeclampsia, hypertensive disorders, nephropathy, or thrombophilia.
  • Specific medications, including ACE inhibitors, NSAIDs, or trastuzumab.
  • Infections such as TORCH, gastrointestinal tract infections, and chronic diarrhoea.

Diagnosis of Oligohydramnios: 

Oligohydramnios is typically diagnosed through ultrasound examinations, focusing on two key measurements: 

  • An amniotic fluid index (AFI) of less than 5cm 
  • Single deepest pocket (SDP) measurement of less than 2cm

Upon diagnosis, a thorough investigation of the maternal history and potential underlying causes is crucial to ensure the health and well-being of both the mother and the developing fetus.

 

several tests aid in evaluation:

1. Nitrizine and Ferning tests for premature rupture of membranes (PROM): 

premature rupture of membranes (PROM) refers to the breaking of the amniotic sac before labour begins. nitrizine and ferning tests are techniques used to assess whether amniotic fluid is leaking.

 

2. Fetal anomaly assessments through ultrasound and, if required, MRI scans: 

Ultrasound scans are commonly used during pregnancy to assess fetal development and detect any potential anomalies.

 

3. Alpha-Fetoprotein (AFP) checks, along with placental and blood tests: 

Alpha-fetoprotein (AFP) is a protein produced by the fetus and is found in the mother’s blood. AFP levels can provide information about the health of the fetus.

 

Treatment of oligohydramnios:

Effective treatment approaches may include:

  • Amnioinfusion: Introducing 200ml of saline into the amniotic sac to increase the levels of amniotic fluid. 
  • Promoting oral hydration to enhance amniotic fluid levels. 
  • Surgical interventions may be required in a few cases to address the underlying issues, such as blockages in the urinary tract, to ensure proper urine flow and subsequent amniotic fluid production. 

Monitoring fetal well-being and managing the condition

Regular non-stress tests (NST) or SDP measurements: non-stress tests (NST) and single deepest pocket (SDP) measurements are monitoring techniques used to assess the well-being of the fetus.

It is recommended to plan for delivery between 36-37 weeks. this is to ensure that:

 

  • The baby’s well-being is maintained 
  • Appropriate management of potential complications well in time.

Complications

Oligohydramnios Can Lead To Various Complications, Including Cord Compression, Facial Distortion, Clubfoot, Pulmonary Hypoplasia, Intrauterine Growth Restriction (IUGR), And Potter Syndrome.

Conclusion

In understanding oligohydramnios and its diverse aspects, doctors can proactively diagnose, manage, and potentially mitigate its effects on fetal and maternal health. By staying informed about the latest advancements in medical knowledge and incorporating timely interventions, the medical community can strive to optimize pregnancy outcomes for both mother and baby.

 

Comment:

 

Given situations like oligohydramnios and other potential complications, especially heightened during the current monsoon season, expectant mothers must exercise meticulous care. This involves upholding optimal hygiene practices, refraining from consuming street food, regularly consulting their obstetricians, and diligently adhering to prescribed medication. Informing both patients and their families about these conditions is essential, prompting them to provide unwavering support, cultivate a stress-free atmosphere, and strictly adhere to the recommended antenatal care (ANC) routine.

Author: Dr Darshit Patel, MD General Medicine

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