Low Fetal Weight in Twin Pregnancies: Risks and Remedies

Low fetal weight

Hello, doctor.
I am currently 34 weeks pregnant with twins.
The measured fetal weights are only 1300g and 1400g, which are considered underweight.
However, I have undergone placental function tests, and the healthcare provider mentioned that contractions and fetal movements are normal.
My weight has increased from 51kg to 63kg since the beginning of the pregnancy, and I consistently consume red meat and fruits each week, along with daily intake of eggs and dairy products.
All my blood tests and urine tests have returned normal results.
Could you please explain why this situation might occur and how I can remedy it? What are the risks associated with underweight fetuses? What should I do now? Additionally, is there a significant difference in performing Group B Streptococcus screening? Thank you for your guidance as a first-time pregnant woman.

Mimi, 20~29 year old female. Ask Date: 2009/09/15

Dr. Lü Lizheng reply Obstetrics and Gynecology

Dear Mimi,
Common reasons for low fetal weight include the following:
First, there may be measurement errors in ultrasound assessments, which do not necessarily indicate that the fetal weight is truly low.
It is advisable to have multiple measurements taken at different hospitals by different physicians to reduce discrepancies.
Second, genetic factors may play a role.
If you or your husband have a smaller body frame, the fetal weight may also be lighter.
Third, there could be discrepancies in gestational age.
If previous measurements consistently indicate that the fetus is one or two weeks smaller, it may suggest that you are actually less than 34 weeks pregnant, which would naturally result in lower weight.
Fourth, twins or multiples typically weigh less because they share nutrients from the mother simultaneously.
Fifth, a small number of fetuses may have insufficient placental function, leading to reduced nutrient supply and smaller size.
Assessing umbilical cord blood flow and monitoring amniotic fluid levels can help in this evaluation.
If placental function is severely compromised to the point of threatening fetal safety, early delivery may be considered.
Sixth, in rare cases, fetuses may be underweight due to congenital abnormalities or infections.
It may be worthwhile to consider a high-level ultrasound or blood tests, and further discussion with your physician is recommended to confirm the cause and take appropriate action.
Regarding Group B Streptococcus screening, approximately 10% of pregnant women will test positive.
Fortunately, most infants have good immunity, and the actual incidence of illness due to Group B Streptococcus infection is only about 1 in 1,000.
If your financial situation allows, it is still advisable to undergo Group B Streptococcus screening.
Sincerely,
Dr.
Li-Cheng Lu
Attending Physician, Department of Obstetrics and Gynecology
Taoyuan Hospital, Ministry of Health and Welfare

Reply Date: 2009/09/15

More Info

Low fetal weight in twin pregnancies can be a concerning issue, especially when the measurements indicate that the fetuses are significantly below the expected weight for their gestational age. In your case, at 34 weeks, weights of 1300g and 1400g are indeed considered low for twins. There are several factors that can contribute to this situation, and understanding them is crucial for managing the pregnancy effectively.

Causes of Low Fetal Weight in Twin Pregnancies
1. Measurement Errors: Ultrasound measurements can sometimes be inaccurate. It is advisable to have multiple assessments from different healthcare providers to confirm the weights.

2. Genetic Factors: If you or your partner have a smaller body frame, it is possible that the fetuses may also inherit this trait, resulting in lower weights.

3. Gestational Age Miscalculation: If there is a discrepancy in the gestational age, the fetuses may appear smaller than expected. Regular monitoring can help clarify this.

4. Nutritional Factors: Although you mentioned a balanced diet rich in red meat, fruits, and dairy, it is essential to ensure that you are meeting the increased caloric and nutritional demands of a twin pregnancy. Consulting with a nutritionist can provide tailored advice.

5. Placental Insufficiency: This is a serious concern where the placenta does not provide adequate nutrients and oxygen to the fetuses. Monitoring blood flow through the umbilical cord and assessing amniotic fluid levels can help evaluate placental function.

6. Congenital Anomalies or Infections: Rarely, fetal growth restriction can be due to congenital issues or infections. Further testing, such as high-level ultrasounds or blood tests, may be warranted.

Risks Associated with Low Fetal Weight
Low fetal weight can lead to several risks, including:
- Increased Risk of Preterm Birth: Smaller fetuses may be more likely to be born prematurely.

- Complications at Birth: Low birth weight can lead to difficulties in breathing, feeding, and maintaining body temperature.

- Long-term Developmental Issues: There may be an increased risk of developmental delays or health problems later in life.

Recommended Actions
1. Regular Monitoring: Continue with regular ultrasounds and check-ups to monitor fetal growth and placental function.

2. Nutritional Support: Work with a healthcare provider or nutritionist to ensure you are consuming enough calories and nutrients. This may include increasing protein intake and ensuring adequate hydration.

3. Stress Management: Reducing stress can positively impact fetal health. Consider relaxation techniques such as prenatal yoga or meditation.

4. Consult Specialists: If there are concerns about placental insufficiency or fetal health, consulting a maternal-fetal medicine specialist may be beneficial.

5. Consider Group B Streptococcus Screening: While about 10% of pregnant women may test positive for Group B Streptococcus (GBS), the risk of serious infection in the newborn is relatively low. However, if you have a positive test, antibiotics during labor can significantly reduce the risk of transmission to the baby.

Conclusion
In summary, while low fetal weight in twin pregnancies can be concerning, understanding the potential causes and risks can help you and your healthcare team take appropriate actions. Regular monitoring, nutritional support, and open communication with your healthcare providers are key to managing your pregnancy effectively. If you have any further questions or concerns, do not hesitate to reach out to your healthcare provider for personalized advice and support.

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