Professor Frederic Amant of the Katholieke Universiteit Leuven (K.U.Leuven) directs research into the treatment of cancer in pregnant women and the consequences of such treatment on foetal development.

In her PhD dissertation on chemotherapy during pregnancy, Kristel Van Calsteren has concluded that there is no increased risk of congenital defects in children who are exposed to chemotherapy during pregnancy. Nor do these children suffer from any discernible negative effects in the long term.

The primary explanation for this reassuring discovery is that the placenta functions as a filter for most of the products researched and that it protects the foetus against the damaging effects of chemotherapy. A second important criterion is that chemotherapy is not administered during the first trimester, which is the most vulnerable period of a pregnancy. A team of paediatricians and psychologists intensively monitored 64 children. This is the very first time such research has been conducted.

A special research project was established in 2004 to acquire better insights into the complex issue of cancer during pregnancy.

The first part of this project examined the treatments that are currently administered to pregnant women with cancer. Furthermore, it researched the influence of these therapies on foetal development and the health of the child at birth.

In cases of specific types of cancer and specific cancer treatments, growth retardation in the womb was observed, but the children made up for this delay after birth. However, the researchers' most important discovery is that the number and types of congenital defects are no different in cases where chemotherapy was administered to mothers. These reassuring findings will be published in the leading scientific periodical 'Journal of Clinical Oncology'.

The second part was of a pharmacological nature; it analysed the "pharmacokinetics" of chemotherapy drugs in pregnant women (i.e. the absorption, progression and distribution of the medication in the body) and the "transplacental transfer" of the medication (transfer through the placenta) to the foetus.

Kristel Van Calsteren's dissertation demonstrates that physiological changes during pregnancy result in lower maximum concentrations of chemotherapy and in reduced exposure to chemotherapy. It appears that the medication is distributed over a greater volume and is also excreted more quickly by the body. Further research is necessary to determine whether this results in the medication having less impact on the tumour, and thus to evaluate whether chemotherapy is sufficiently efficacious.

Initially, the researchers had no notion of the quantity of chemotherapy that reaches unborn children. For this reason, they closely examined the transfer of chemotherapy through the placenta in animals. The results indicated that this transfer differs significantly depending on the type of medication. Some medications barely penetrate the placenta, while in cases of other drugs the same concentration is found in both the mother and foetus. The research indicates that the placenta acts as a filter for most tested chemotherapy drugs and thus reduces the foetus's exposure to chemotherapy. These discoveries are directive and reassuring.

The third part focused on the effects of prenatal exposure to chemotherapy on the general and neurological development of the child. The researchers established international co-operation with the universities of Nijmegen and Prague. The children were examined by pediatric neurologists and neuropsychologists in the same ways at the three centres. The results are based on the clinical examination of 64 children who were exposed to chemotherapy during pregnancy. The majority of them are under 6 years old, while the oldest child is 15.

This research indicated that most of the children were in a normal condition at birth. As they grew older, the children's development was in accordance with the expectations for their age. Specific tests of their memory and attentional functions did indicate increased impulsivity in these children, however. This has previously been described in children born prematurely and children exposed to their mothers' increased psychological stress during pregnancy. These factors also play a role in women to whom chemotherapy is administered during pregnancy.

Source: K.U.Leuven