What Causes Slow Fetal Growth During Pregnancy

What do we say when people ask us, “Who do you want, a son or a daughter?” Most to-be moms have just one answer: “Doesn’t matter, I just want a healthy baby.” Isn’t it? The wellness of the fetus is that important for its mother.

Do you know that even after taking proper care during pregnancy the fetus could, sometimes, grow slow? We tell you about the causes of fetal growth restriction, the possible risks, and the preventive measures you can take.

What Is Fetal Growth Restriction?

Intrauterine growth restriction (IUGR), which is a condition signifying the slow growth of a baby during pregnancy. In this condition, the size of the baby is smaller than the average size at that pregnancy age.

Different Types Of IUGRs During Pregnancy

There are two main types of intrauterine growth restrictions occurring during pregnancy:

  1. Symmetrical or primary IUGR: The baby has a symmetrical body in proportion with the internal organs, but is smaller than the size of a normal baby of that age.
  2. Asymmetrical or secondary IUGR: The baby has a normal head and brain but a smaller body than what it should be at that gestational age. This condition is not evident until the third trimester.

IUGR could be the result of certain health issues in the mother.

Reasons For Restricted Growth Of Fetus During Pregnancy

The causes of IUGR are segregated into three broad categories: maternal, fetal and placental.

  • Maternal health is important for the baby to get all the essential nutrients for its growth.
  • Fetal health is necessary to make sure the baby receives the nutrients supplied by the mother.
  • The placenta should be healthy enough to carry the nutrients from the mother to the fetus.

All the factors mentioned below fall into one of the three categories:

  1.  Pregnancy-induced hypertension: During pregnancy, your blood pressure is constantly monitored to check for hypertension. An increased blood pressure may indicate hypertensive disorder of pregnancy (gestational hypertension, chronic hypertension preeclampsia). The flow of blood to the placenta is reduced, cutting down on the supply of sufficient oxygen and supplements to the fetus, thereby leading to slow fetal growth.
  2. Multiple pregnancies: In some cases of multiple pregnancies, the slow fetal development is because of the inefficiency of the placenta to meet the nutritional demands of the multiple babies. Moreover, the chances of hypertensive disorder are also high in multiple pregnancies. IUGR occurs in 25-30% of twin pregnancies.
  3. Infections: Any infections transferred from the mother during pregnancy can lead to slow fetal growth. Infections such as syphilis (a sexually transmitted bacterial infection), toxoplasmosis (a parasitic infection transmitted mainly through under-cooked meat), cytomegalovirus (viral infection with significant impact during pregnancy due to weaker immunity), and rubella (German measles) increase the chances of IUGR.
  4. Lower level of amniotic fluids: It is necessary to have sufficient amniotic fluid in the sac for normal fetal development to happen. However, low fluid level (also termed as oligohydramnios) can lead to fetal growth restriction. Various factors, including the health of the mother, certain medications, and a slight rupture of the amniotic sac cause the fluid levels to deplete.
  5. Placental insufficiency: In this condition, the placenta does not work properly. This leads to insufficient supply of oxygen and nutrients to the baby from its mother, resulting in slow growth.
  6. Abnormalities of the umbilical cord: The cord connects the fetus with the placenta. It contains one umbilical vein and two umbilical arteries, which carry blood between the fetus and the placenta. However, if there is only one artery in the umbilical cord, then this abnormality leads to fetal growth restriction.

7. Other maternal and fetal reasons include:

  • Small size of the mother,  leading to constitutionally small baby
  • The mother’s nutritional intake during pregnancy
  • Abnormal shape or size of the womb
  • Chronic illness in the mother such as sickle cell disease, diabetes, hypertension, heart disease 
  • Chromosomal abnormalities such as Turner Syndrome and Down Syndrome in the fetus
  • Genetic and skeletal abnormalities in the fetus

Slow fetal growth can also occur due to the lifestyle of the mother, such as if she:

  • smokes
  • is underweight
  • drinks alcohol
  • takes drugs
  • follows poor diet
  • is exposed to high doses of radiation or chemicals

During your antenatal checkup, the doctor will measure the fundal height to determine the size of the baby.

Your baby’s size will be monitored throughout the pregnancy, and the measurements will be put on a growth chart. If the doctor finds any abnormality, she does an ultrasound scan to measure the baby’s growth accurately.

Fetal growth measurement is important because slow growth could lead to certain health problems in the baby.

Risks Of IUGR

Babies with IUGR have increased chances of getting health issues both before and after birth. The risks include:

  • Low birth weight
  • Problems with breathing and feeding
  • Decreased ability to fight infection
  • Hypoglycemia (low blood sugar level)
  • Low Apgar Scores (Apgar score is a test carried out to evaluate the physical condition of the newborn and to determine any immediate need of medical care. The score is determined on a scale of 0 to 2, with 2 being the best)
  • Abnormally high red blood cell count
  • Neurological problems
  • Trouble in maintaining the body temperature
  • Stillbirth

In order to avoid these risks in the baby, the doctor measures the fetal growth regularly when you go for health check-ups.

How Is Fetal Growth Restriction Diagnosed?

The fetal size can be estimated by measuring the fundal height. However, there are other procedures to diagnose IUGR and assess the baby’s health:

  1. Ultrasound: An ultrasound uses sound waves to create images of the baby’s structure and measure its head and abdomen. These measurements are compared with the growth chart to estimate the fetal weight.
  2. Doppler flow: The technique is used to measure the speed and amount of blood flow into the blood vessels of the fetal brain and the umbilical cord, using sound waves.
  3. Weight checks: It is another way of estimating the fetal growth. During every prenatal visit, the doctor will check and record the mother’s weight. If the expecting woman is not gaining appropriate weight, it could result in fetus’ slow growth.Slow fetal growth can be effectively managed in expecting mothers through regular checkups and healthy lifestyle.

How Is IUGR Managed?

IUGR is managed based on its severity. It depends on the gestational age at which it is diagnosed. IUGR can be divided into early onset IUGR and late onset IUGR, depending on whether its occurring prior to 34 weeks or after that. According to the fetal compromise, IUGR is divided into stages I-IV based on the effective fetal weight, cerebroplacental ratio, uterine artery PI, flows in ductous venosus and management based upon the stage and gestational age at diagnosed management can be planned. 

  • Stage 0: You are treated as an outpatient with Doppler test done every two weeks. If the results are consistent, your delivery can be at term. But if the Doppler results are abnormal, the fetus moves to Stage I.
  • No IUGR: Where the baby is constitutionally small but the doppler parameters are normal, pregnancy can be taken until 40 weeks. Labor may be induced at 40 weeks if the patient does not go into labor by 40 weeks and there are no contraindications for normal vaginal delivery. If the gestational age is less than 40 weeks, the mother is monitored weekly until 40 weeks and induction is done earlier in the case of any deterioration.   
  • Stage I: Weekly monitoring is required until 37 weeks and induction for labor is done if no contraindications for normal vaginal delivery. 
  • Stage II: Stricter monitoring is needed every two to three days. Delivery is done by cesarean section (CS) as the baby is unable to withstand the stress of labor. This is usually advised at 34 weeks.
  • Stage III: Monitoring every 24-48 hours and mode of delivery is usually via CS usually at 30 weeks after steroid cover.
  • Stage IV: Monitoring every 12-24 hours and delivery via CS at gestational age more than 26 weeks. Long-term prognosis remain poor due to extreme prematurity. 

If your doctor suspects IUGR, then:

  • You will have regular scans to check your baby’s growth. With a Doppler test, the amount of blood flow from the placenta to the fetus is checked.
  • If there is any concern about the fetal growth, your doctor will recommend CTG monitoring, regular scans, and consultant appointments.
  • You will be advised to monitor the movements of your baby closely.
  • If growth restriction is severe, then the doctor may recommend an early delivery by C-section as vaginal delivery would be stressful. In such case, your baby will be put in the neonatal care unit, where it can grow better than inside your womb.

Above all, you need to take care of yourself by eating nutritious food and taking ample rest.

What Should You Do In The Case Of IUGR?

Visit your doctor regularly and get carefully checked. Closely monitor your baby’s movement patterns. If your baby does not move very often, contact your doctor and follow their instructions.

Ask your doctor several questions such as,

  • What activities should you avoid?
  • What precautions should you take?
  • What symptoms or problems you should watch out for?

There is little you can do to control IUGR, but certain lifestyle changes could be of help.

How To Prevent IUGR?

The below measures can reduce the risk of IUGR:

  • Eat a healthy diet. Healthy foods provide proper nourishment to your baby.
  • Quit smoking and drinking alcohol during pregnancy.
  • Limit the intake of caffeine.
  • Check with your doctor if any medications that you are taking pose a risk of IUGR.
  • Get plenty of rest and keep stress at bay. Try to get at least eight hours of sleep every day.
  • Stay fit by exercising.

Slow fetal growth is not in your hands. But what you can do is have a healthy lifestyle, exercise and keep away from unhealthy habits such as smoking. Talk to your doctor and follow their instructions. If the fetal growth is still slow, all you can do is wait for the baby to come out of your womb. Breastfeeding and careful nurturing could help you do the damage control.

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