Web Date: May 13, 2013
Urine Test May Detect Pregnancy Problems
By analyzing metabolites in the urine of expectant mothers, doctors could diagnose problems in pregnancy earlier than with current tests, according to a new study (J. Proteome Res. 2013, DOI: 10.1021/pr4002355).
Currently, urine analysis has limited use in prenatal testing. Doctors use it to diagnose maternal infections or to look for proteins in urine that signal preeclampsia, a condition that causes high blood pressure in pregnant women. A team led by Ana M. Gil at the University of Aveiro, in Portugal, decided to look at the full range of metabolites excreted in urine to see if they could find ones that indicate potential complications in pregnancy.
The team took urine samples from 300 pregnant women in their second trimester and stored the samples until the end of the pregnancies. Some women went on to be diagnosed with specific complications. Others had no problems.
After the women gave birth, Gil and her colleagues analyzed each urine sample using nuclear magnetic resonance spectroscopy. The researchers then performed a statistical analysis on the NMR data to compare urine from the women with a certain complication to that of mothers who had no issues. From this analysis, the researchers identified characteristic patterns of NMR peaks that corresponded with preeclampsia, preterm delivery, gestational diabetes, fetal malformations, and the chromosomal disorder trisomy 21, which causes Down syndrome.
For some of the conditions, the team could connect the NMR signatures with specific metabolites by comparing peaks in the signatures to those in the spectra of known metabolites. For example, women who went on to suffer preeclampsia showed lower levels of fumarate, acetate, and formate—compounds not previously linked to the condition.
Some of the complications identified by the NMR technique aren’t easy to diagnose in the second trimester using conventional tests. The researchers could find an NMR signature linked to gestational diabetes, which usually is tough to detect through blood tests before 24 weeks into a pregnancy. They also found differences in amino acids present in the urine of women who went on to have intrauterine growth restriction, which stops the fetus from growing properly. Gil says doctors often don’t detect this condition until later in a pregnancy.
The urine tests also revealed differences in the levels of glucose and certain amino acids in women whose babies had trisomy 21. Doctors usually diagnose this disorder with an invasive procedure such as amniocentesis, in which they collect fetal cells from the amniotic fluid surrounding the fetus with a needle.
Warwick Dunn, an expert in the study of metabolites at the University of Birmingham, in the U.K., says that the researchers next need to test a larger and more geographically diverse population of women to determine if the NMR method is clinically useful. More testing is necessary, he says, because the types and levels of metabolites in urine can change based on a wide range of conditions, including diet or other lifestyle choices. But if the NMR technique can be validated, he believes it will help identify pregnancies at risk.
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