Fetal growth restriction adversely affects both maternal and fetal development. What exactly causes this condition, and how can it be addressed? Let's explore below.
What causes slow fetal growth?
Intrauterine growth restriction (IUGR) is a significant obstetric complication with an incidence rate of 3%–10%, averaging approximately 6.4%—a notably high prevalence.
Intrauterine growth restriction (IUGR) refers to restricted fetal growth within the uterus, resulting in a size inconsistent with gestational age. This is primarily manifested by fetal weight below the normal range for the same gestational week, with birth weight under 2500 grams after 37 weeks of pregnancy.
The etiology of this condition is complex, with approximately 30% of cases remaining unexplained. Known causes include:
① Intrauterine infection with TORCH pathogens (Toxoplasma, Cytomegalovirus, Rubella virus, Herpes simplex virus, and other pathogens), accounting for about 10%;
② Fetal chromosomal abnormalities, occurring in approximately 10% of cases;③ Maternal conditions such as preeclampsia, chronic hypertension, and chronic nephritis, which impair placental blood supply, leading to chronic fetal hypoxia and impaired growth and development. Severe maternal anemia, cardiopulmonary diseases, and cholestasis may also adversely affect fetal growth and development;④ Maternal malnutrition, particularly insufficient protein and caloric intake, is a major factor affecting fetal growth and development, accounting for approximately half of all cases; ⑤ Unhealthy lifestyle habits, such as smoking (including secondhand smoke exposure), alcohol abuse, and drug use, are also contributing causes of fetal intrauterine growth restriction.
Manifestations of Fetal Growth Restriction
The primary impression of a fetus with intrauterine growth restriction is low birth weight. Consequently, many believe that a smaller newborn is not a concern, assuming proper postnatal feeding will ensure healthy growth. This mindset is misguided.Fetal growth restriction falls into two categories: the malnutrition type and the hypoplasia type. The malnutrition type is often caused by factors affecting the fetus during mid-pregnancy or later, such as preeclampsia or multiple pregnancies, while embryonic development is normal during early pregnancy. Its characteristic features include signs of malnutrition in the newborn's appearance, with a weight significantly below that of normal newborns of the same gestational age, while head circumference and height remain normal.For these infants, enhanced postnatal feeding can help achieve near-normal physical development, resulting in generally favorable neonatal prognosis. In contrast, the causative factors for dysplastic IUGR affect the embryo during early pregnancy, causing damage that impairs fetal growth and development. Examples include genetic factors and TORCH infections, which can lead to fetal malformations and other defects.Characteristics of the hypoplastic type include symmetrical development of birth weight, length, and head circumference, though these measurements are significantly below the average expected for a normal newborn of the same gestational age. Infants with this type have a higher incidence of congenital malformations and often exhibit chromosomal number or structural abnormalities, some of which can be life-threatening. Therefore, fetal growth restriction is not merely a matter of low birth weight; it may involve infants with malformations.
How can fetal growth restriction be detected?
Pregnant women and their families can monitor this condition through three primary methods. The simplest approach is weight measurement: during late pregnancy, maternal weight gain should average approximately 0.5 kg per week. If weight gain slows or stagnates without significant changes in clothing size, intrauterine growth restriction should be suspected.The second method is fundal height measurement. Using a soft tape measure, measure the height from the midpoint of the upper edge of the symphysis pubis to the top of the uterus. Plot this measurement on a fundal height chart (also known as a pregnancy chart) weekly. If measurements fall below the low weight curve or below the curve for 2-3 consecutive weeks, fetal intrauterine growth restriction can be suspected.The third method is the fetal growth index, calculated as: Uterine height (cm) - (3 × gestational months) - 1 A difference value below -3 indicates possible IUGR; Between -3 and 3 indicates normal fetal weight; Above 3 suggests possible macrosomia. Pregnant women who suspect IUGR through self-assessment should seek further confirmation at a hospital.
Management of Fetal Intrauterine Growth Restriction
1. Rest in left lateral position. Follow a high-protein diet to enhance nutrition.
2. Intermittent oxygen therapy. 1 hour per session, 2–3 times daily.
3. Pharmacological treatment
(1) Salbutamol 2.4mg orally, 3 times daily. 7 days constitute one treatment course.
(2) Low-molecular-weight dextran 500ml and Salvia miltiorrhiza injection 8-16ml added to 250ml 5% glucose solution for intravenous drip, once daily. A 7-day course is recommended. This aims to improve microcirculation and placental function.
(3) Compound amino acid solution 100ml, intravenous injection, once daily. A 7-day course is recommended.
4. Enhanced Monitoring
(1) Observe fetal movements 3 times daily.
(2) Fetal monitoring: Perform NST at least weekly. Conduct OCT for NST non-reactive cases. Terminate pregnancy as appropriate for positive OCT results.
(3) Ultrasound monitoring: Assess amniotic fluid index or maximum amniotic fluid pocket depth weekly.
(4) Urinary E3 or E/C ratio measurement: Weekly.
5. Obstetric Management
(1) If fetal growth and placental function remain favorable after treatment, pregnancy may continue but must not exceed the estimated due date.
(2) If treatment is ineffective and fetal-placental function tests show abnormalities, administer prednisone or dexamethasone 1–2 days before delivery to promote fetal lung maturation, followed by prompt termination of pregnancy.
(3) Immediate cesarean delivery is indicated in the following situations: ① NST shows non-reactive pattern with positive CST.② Ultrasound-detected oligohydramnios with meconium staining grade II or higher. ③ Mothers with fetal growth restriction complicated by other high-risk factors, severe disease, or obstetric abnormalities.
6. Management of Intrauterine Growth Restricted Newborns
(1) Prepare all emergency measures before delivery.
(2) Immediately after delivery, thoroughly clear amniotic fluid and meconium from the airway via endotracheal intubation to prevent respiratory distress syndrome (RDS).
(3) Maintain body warmth.
(4) Administer glucose solution or initiate breastfeeding as early as possible.
Fetal growth restriction poses significant risks—expectant parents should be vigilant.