Platelets – or platelets – are the smallest cells in the blood that play an important role in blood clotting. Due to various causes, including pregnancy, their numbers may go up or down.
Function and life of platelets
Platelets ensure that any injury to a blood vessel is immediately closed by supporting each other and the vessels’ walls. They release different coagulation factors. Platelets’ activity forms scabs on open wounds – a process that takes about six minutes in healthy people.
In the bone marrow, constantly new platelets are formed, whose life varies between eight and twelve days. After that, they are broken down mainly in the spleen and, to a lesser extent, in the lungs and liver.
How is the platelet count going?
Regular blood tests of the mother are among the precautionary routines in pregnancy, while the number of platelets is counted and recorded in the passport. The platelets’ counting takes place in a counting chamber (hemocytometer) by a light microscopic procedure. It is formed by two parallel glass plates, which lie one above the other at a small distance.
The base plate has certain surface structures as well as bar marks, creating spaces with defined volumes. In these, a particle suspension is introduced, its microscopic count and the chamber’s volume results in the particles’ concentration – in this case, the number of platelets in one microliter of blood.
Pregnancy-associated thrombocytopenia – not too rare in the last trimester
In about six to eight percent of healthy women, especially in the last trimester of pregnancy, reduces the number of platelets; this process is referred to as “pregnancy-associated thrombocytopenia” or “gestational thrombocytopenia.” After birth, the number of platelets normalizes again. The causes are not yet known – but medical experts assume that here two factors play a role:
- The new formation and the degradation of the platelets are accelerated during pregnancy. Therefore, the blood of pregnant women contains sometimes less, but younger and larger platelets.
- During pregnancy, the blood volume increases, which means that the mother’s body produces more blood plasma. Therefore, fewer blood platelets are present per milliliter of blood, which does not influence their performance.
- If the doctor determines at the blood test that the number of platelets reaches a low range, he will repeat the test at short intervals to see if their numbers continue to fall.
What are the risks associated with a low platelet count?
Thrombocytopenia during pregnancy is usually not dangerous and does not affect the baby’s blood count or care. Also, physical symptoms are not connected; therapy is not required. Very low platelet counts can lead to increased bleeding during or after birth, but the risk is also complicated for clinicians to assess.
From a Caesarean section, if the platelet count per microliter of blood falls below the value of 50,000 is discouraged. However, in most affected women, pregnancy-related thrombocytopenia is not very pronounced.
In some cases, a decreasing number of platelets is a sign of a more serious pregnancy complication: The hallmarks of HELLP syndrome are red cell disintegration, increased liver function, and decreased blood clotting. The number of platelets falls below 100,000 per microliter of blood; in medical texts, cases are described in which their number had even dropped to a value below 20,000.
A HELLP syndrome can develop very rapidly; it is associated with other symptoms – mainly pain in the right upper abdomen, high blood pressure, and water retention in the extremities. When it occurs, the pregnancy is almost always terminated by an emergency cesarean section. A frequency of 0.2 to 0.85 percent makes it a rare pregnancy disorder. However, in pregnant women whose platelet count per milliliter of blood is less than 75,000 to 100,000, their doctor will safely initiate more extensive investigations to rule out pre-eclampsia or incipient HELLP syndrome.
Too many platelets in pregnancy?
Also rare is thrombocytosis in pregnancy, in which the number of platelets exceeds the norms upward. It can be triggered by infections, physical exertion, metabolic disorders, iron deficiency, or the pregnancy itself. Thrombocytosis increases the risk of blood clots forming in the blood vessels and, thus, the risk of thrombosis or stroke. A severe severity is not to be expected during pregnancy.
Nutritional changes, copious drinking, sufficient exercise, the elimination of any iron deficiency – with appropriate dietary supplements only after a doctor’s prescription, as too much iron can be dangerous for the baby – as well as relaxation exercises or acupuncture treatment can counteract a pregnancy-related thrombocytosis.
- Especially in the last trimester of pregnancy occurs in six to eight percent of pregnant women to a decrease in platelets.
- In most cases, this phenomenon is due to blood circulation changes during pregnancy and is not dangerous for the mother or child. However, at deficient levels, bleeding may increase during and after birth.
- In the case of very severe platelet degeneration, other complications of pregnancy should preclude pregnancy complications (preeclampsia, HELLP syndrome).
- The physical strain of pregnancy can also cause the number of platelets to exceed the normal range.