MUMS-TO-BE who suffer from the same severe morning sickness that Kate Middleton was treated for have an increased risk of a number of complications if they have the condition during the second trimester of pregnancy, research suggests.
There is a higher risk of preterm pre-eclampsia, premature separation of the placenta or having a small baby if hyperemesis gravidarum is onset during the second trimester of pregnancy, researchers said.
In December Kate was admitted to hospital suffering from the condition -- a rare illness which causes severe vomiting during pregnancy. It occurs in 0.5 to 3pc of pregnancies and is caused by high levels of the pregnancy hormone, human chorionic gonadotropin (hCG), and a woman's sensitivity to it.
It is most common in the first 12 weeks of pregnancy and often eases off in the middle trimester.
New research out today suggests that having the condition during the second trimester can lead to some placental complications.
The study, published in BJOG: An International Journal of Obstetrics and Gynaecology, examined data from the Swedish Medical Birth Register between 1997 and 2009.
Data from 1,155,033 women showed that 1.1pc of them suffered from hyperemesis gravidarum before they were 22 weeks pregnant. Women who had the condition in the second trimester had a doubled risk of preterm pre-eclampsia -- 0.6pc of women without hyperemesis gravidarum suffered from the condition compared to 1.4pc of those who did. They also had a threefold risk of placental abruption --0.4pc compared to 1.1pc -- and a 39pc risk of having a small baby.
Co-author of the study Marie Bolin of Uppsala University in Sweden, said: "The results indicate that pregnancies with hyperemesis gravidarum in the second trimester demand an increased alertness and supervision during the pregnancy for development of any adverse outcomes associated with abnormal placentation."