Intrauterine growth restriction (IUGR) is a pregnancy complication that occurs in about 10 to 15% of pregnancies worldwide that can cause a low birth weight, long-term consequences for the newborn and in some cases, fetal mortality.
There is a higher risk of IUGR in FNAIT-affected pregnancies, reportedly due to placenta deterioration due to the impact of maternal anti-HPA-1a antibodies.
What is FNAIT?
Fetal and neonatal alloimmune thrombocytopenia (FNAIT) is a rare but serious condition that affects 0.1% of pregnancies in which a pregnant mother’s immune system produces antibodies against the platelets of her fetus. This occurs when a fetus inherits platelet antigens from the father that are not compatible with the mother, typically involving a protein called human platelet antigen (HPA). The mother’s immune system recognizes the fetal platelets as foreign, attacking and destroying them, leading to low platelet levels (thrombocytopenia) in the fetus or newborn.
What is intrauterine growth restriction?
Intrauterine growth restriction (IUGR) is when the fetus doesn’t grow at the expected rate during pregnancy. It is defined as a birth weight under the 10th percentile. It has a number of causes, namely problems with the placenta, restricted blood flow via the umbilical cord, maternal infection, smoking, drinking alcohol, maternal medical conditions such as high blood pressure, lupus or anemia, living at high altitude and genetic disorders or birth defects in the baby.
There are two types of IUGR:
- Symmetrical IUGR: when the baby is small in size.
- Asymmetrical IUGR: when the baby’s head and brain are of standard size, but the body is smaller than expected.
IUGR can be detected during pregnancy via a prenatal ultrasound. Doctors use the high-frequency sound waves to measure the fetus’s size and weight.
How does it affect infants with FNAIT?
In FNAIT-affected pregnancies, there is evidence that there is a greater risk of IUGR occurring, particularly in severe cases of FNAIT. This can lead to lower birth weight, and in some cases, miscarriage. Following delivery, the newborn may require specialist care in the neonatal intensive care unit (NICU) and may experience symptoms such as breathing difficulties, trouble feeding, low blood sugar and a fluctuating body temperature.
Long-term consequences may include a higher risk of cardiovascular and renal disease, type 2 diabetes, metabolic syndrome, nonalcoholic fatty liver disease and neurological abnormalities.
It is thought to occur in FNAIT pregnancies as a result of the maternal anti-HPA-1a antibodies not just attacking fetal platelets, but also cells of the placenta, causing placental defects.
How is IUGR treated in FNAIT-affected pregnancies?
If IUGR is confirmed, close monitoring throughout the pregnancy is required by regular ultrasounds to track the fetus’s movements and growth rate as well as placental function.
The use of intravenous immunoglobulin (IVIG) has been reported, but requires more study, with no known complications for the baby.
The pregnant mother will likely be advised to stay on bed rest to improve blood flow to the baby, eat a healthy diet, get plenty of sleep and avoid alcohol, drugs and tobacco. A cesarean delivery may also be advised in some cases.
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