Low Amniotic Fluid and Neural Tube Defects in Pregnancy

Oligohydramnios and neural tube defects?

Hello Doctor, I am currently 19 weeks pregnant.
During my 14-week check-up, the doctor informed me that there is a low level of amniotic fluid, which was visually assessed to be well below the minimum index of 8.
The ultrasound did not reveal any other abnormalities in the fetus.
Over the past few weeks, I have been diligently drinking water and using traditional Chinese medicine to improve the amniotic fluid levels, and it seems to have increased slightly.
However, the doctor still says it is too low.
I am wondering if this is related to my uterine fibroids (two measuring 5 cm) and the placenta, as the fetus appears to be quite cramped.
I have consulted several hospitals regarding the amniotic fluid issue; two doctors said it is too low, while two others said it is acceptable (stating that as long as a single quadrant measures over 2 cm, it is okay).
My blood test results show a risk of Down syndrome at 1:31,300, a risk of neural tube defects at 1:39, and a risk of Edwards syndrome at 1:34,500.
The doctor has recommended a referral for a high-level ultrasound.
Should I also undergo amniocentesis? Additionally, I have been taking two 800 microgram folic acid tablets daily from one month before conception until the end of the third month.
Why is the risk of neural tube defects still so high? Thank you.

Zhen Zhu, 30~39 year old female. Ask Date: 2016/09/08

Dr. Cao Guotao reply Obstetrics and Gynecology

Hello, a high-level ultrasound is sufficient.
With a Down syndrome risk value of 1:31,300, amniocentesis is not necessary.
The probability of neural tube defects is low, but let's wait for the results of the high-level ultrasound.
Wishing you good health.

Reply Date: 2016/09/08

More Info

Low amniotic fluid, also known as oligohydramnios, can have significant implications for both the mother and the developing fetus. In your case, at 19 weeks of pregnancy, the concern about low amniotic fluid levels is valid, especially since it has been noted since around 14 weeks. Amniotic fluid plays a crucial role in fetal development, providing cushioning, allowing for movement, and facilitating lung development.
The normal range for amniotic fluid is typically assessed using the amniotic fluid index (AFI), where a score below 8 cm is considered low. The fact that your measurements are consistently below this threshold raises concerns. Low amniotic fluid can be associated with several factors, including placental issues, fetal abnormalities, or maternal health conditions. In your case, the presence of uterine fibroids (two 5 cm fibroids) could potentially contribute to the reduced space for the fetus and possibly affect the placenta's ability to function optimally.
Regarding the neural tube defect (NTD) risk, it is important to note that while taking folic acid (800 micrograms daily) significantly reduces the risk of NTDs, it does not eliminate it entirely. The risk factors for NTDs can include genetic predispositions, maternal diabetes, obesity, and certain medications, among others. The risk value you mentioned (1:39) is indeed concerning and warrants further investigation.
The recommendation for a high-level ultrasound is prudent, as it can provide more detailed information about the fetal anatomy and help assess for any structural abnormalities that could be contributing to the oligohydramnios or the elevated risk of NTDs. As for the question of whether to proceed with amniocentesis, this is a decision that should be made in consultation with your healthcare provider, considering the risks and benefits. Amniocentesis can provide definitive information about chromosomal abnormalities and other genetic conditions, but it also carries a small risk of miscarriage.

In summary, low amniotic fluid and elevated NTD risk are serious concerns that require careful monitoring and possibly further testing. It is essential to maintain open communication with your healthcare team, follow their recommendations for additional imaging and testing, and discuss any concerns you may have about your pregnancy. Staying hydrated, following a balanced diet, and attending all scheduled prenatal appointments will also be crucial in managing your pregnancy effectively.

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