Pregnancy is hard on the body. But for women with two specific genes, it may be especially difficult.
Duchess of Cambridge Kate Middleton famously suffered from hyperemesis gravidarum.Photo: Chris Jackson (Getty Images)
A new study from researchers at the University of California, Los Angeles and University of Southern California identified two genes associated with hyperemesis gravidarum, a rare condition in which a pregnancy involves nausea and vomiting so severe that some women wind up in the hospital. The results, which relied on data from consumer DNA testing company 23andMe, are published in the journal Nature Communications.
A majority of women experience some form of morning sickness. Hyperemesis gravidarum affects somewhere between 0.3 and 2.3 per cent of pregnancies. (If you're a fan of the royals, you may recall that Kate Middleton suffered from the condition during her pregnancies.)
Hyperemesis gravidarum can lead to dangerous dehydration, weight loss and electrolyte imbalances. It's the second largest cause of hospitalisation during pregnancy. When hospitalised, women often require IVs and, in some cases, feeding tubes. Drugs to treat it are largely ineffective and can lead to serious health consequences for mother and baby.
But little is known about why some women experience it and others do not. This new study suggests that it may be, at least in part, genetic. Previous research had shown that severe nausea and vomiting during pregnancy often runs in families. So researchers at UCLA and USC partnered with 23andMe to deduce whether specific genes might be the culprit.
First, they looked at the DNA of 1306 women of European ancestry who reported in an online survey that they have received IV therapy for nausea and vomiting during pregnancy, and compared them to 15,756 participants who did not report any nausea or vomiting during pregnancy. The researchers found that two genes, GDF15 and IGFBP7, appeared to be a commonality among women with the condition.
They then tested their theory on a bigger data set, with 53,731 female 23andMe customers primarily of European descent who reported a range of symptoms from no nausea to very severe nausea during pregnancy. Again, the regions of the genome where the genes GDF15 and IGFBP7 are located were the locations of the strongest signals. Several other regions also showed some significance. In a separate follow-up study, researchers showed that the proteins GDF15 and IGFBP7 are abnormally high in women with hyperemesis gravidarum. Both genes are involved in the development of the placenta and play important roles in early pregnancy and appetite regulation.
Further study will be necessary to prove that the mutations to GDF15 and IGFBP7 are the actual cause of extreme nausea and vomiting in pregnancy, but the study suggests the genes are at least an indication that a woman may be at risk of the condition.
Marlena Fejzo, the study's first author and a researcher at the David Geffen School of Medicine at UCLA, actually experienced the condition herself. Fejzo lost a pregnancy as a result of the condition in 1999, she said in a statement.
Further research will explore whether GDF15 and IGFBP7 protein levels can be altered safely, to allow more women to experience safer pregnancies.