What causes a smaller than normal fetal biparietal diameter?

Generally, a smaller than normal fetal biparietal diameter may be caused by genetic factors, poor nutrition during pregnancy, intrauterine growth restriction, gestational hypertension, placental factors, and other reasons. Symptomatic treatments such as general therapy and medication may be required. If physical discomfort occurs, prompt medical consultation and treatment are recommended. Detailed explanations are as follows:

1. Genetic Factors

If either parent has a small head size or short stature, the fetus may be genetically predisposed to a relatively smaller biparietal diameter. This is a normal physiological variation and typically does not accompany other symptoms. Pregnant women can monitor fetal growth and development through regular prenatal checkups and maintain a healthy lifestyle to provide an optimal growth environment for the fetus.

2. Poor Nutrition During Pregnancy

Insufficient intake of proteins, vitamins, and minerals by the pregnant woman may fail to meet the nutritional requirements for fetal growth and development, potentially leading to a smaller biparietal diameter. Pregnant women should increase their intake of proteins and vitamins by consuming more lean meats, fish, eggs, legumes, fresh vegetables, and fruits. Fetal growth and development should also be monitored regularly.

3. Intrauterine Growth Restriction

Intrauterine growth restriction may be associated with abnormal placental function, diabetes, and other factors that lead to inadequate fetal nutrition supply, affecting normal development of the fetal brain and skull. It may also be accompanied by symptoms such as low birth weight and oligohydramnios. Monitoring fetal growth is recommended, with possible early delivery if necessary, followed by postnatal nutritional support and close monitoring.

4. Gestational Hypertension

Pregnant women with a family history of hypertension or abnormal placental implantation may develop gestational hypertension. This condition can cause vasospasm and narrowing of placental blood vessels, impairing placental blood flow and subsequently affecting fetal growth and development. Symptoms may include elevated blood pressure, proteinuria, and edema. Medications such as labetalol tablets or nifedipine tablets may be prescribed under medical supervision.

5. Placental Factors

Placental pathologies such as placental abruption or placental insufficiency may reduce uteroplacental blood flow, leading to inadequate fetal blood supply, impaired fetal development, and a smaller biparietal diameter. Symptoms may include vaginal bleeding and abdominal pain. Pregnant women should undergo comprehensive prenatal examinations to determine the cause and severity of placental abnormalities. In some cases, cesarean section or hysterectomy may be required.

Pregnant women should undergo regular prenatal checkups to monitor fetal growth and development and follow medical advice for appropriate interventions.

References

[1] Zhou Meiling, Zhang Dirong, Guo Zhijie. The impact of fetal presentation on ultrasound estimation of fetal weight using different formulas [J]. World Journal of Complex Medical, 2022, 8(07): 97-99+103.

[2] Ling Lei, Wang Jue, Qian Lan, et al. Evaluation of fetal brain development using three-dimensional volumetric measurements based on MR images [J]. Chinese Journal of Birth Health & Genetics, 2020, 28(08): 986-991+996.