(PhysOrg.com) -- Researchers in Norway have discovered a form of severe morning sickness known as hyperemesis gravidarum may be passed on from mothers to their daughters.
This type of morning sickness causes severe nausea and almost constant vomiting often leading to weight loss, starting earlier than the 22nd week of the pregnancy. The condition affects around 2% of pregnancies, but it is a frequent reason for hospitalization, and is often linked with premature births and low birth weights. It was previously assumed to have a psychological cause such as subconsciously rejecting the growing fetus or the partner, and even today some women with the condition are still told to stop pretending they are sick, according to the researchers.
The study examined data of 2.3 million pregnancies and births from Norwegian registry data in the period 1967 to 2006, and analyzed the rate of hyperemesis gravidarum in over 544,000 mother/daughter pairings and nearly 400,000 mother/son pairings. All the daughters and sons had children themselves. The medical birth registry is a mandatory register of all births in Norway. Data are collected on a standardized form by the midwife or physician attending the birth, with demographic data, maternal health, any complications, and the conditions of the baby included.
Graduate student Ase Vikanes from the Norwegian Institute of Public Health in Oslo who led the research, said the study showed there was a strong influence of maternal genes on the incidence of hyperemesis gravidarum, with 3% of daughters of afflicted mothers suffering the condition but only 1% if their mothers had not had the condition. Around 1.2% of female partners of men whose mothers suffered the condition also had it.
The daughters of affected mothers were more likely to suffer the condition even if they were born of an unaffected pregnancy. 3% were affected if their mothers had the condition during the pregnancy, 3.2% if they had suffered from it in a previous pregnancy, and 3.7% if they were afflicted in a later pregnancy. The results were not affected by the mother’s age at childbirth, the period of the birth, or whether or not the daughter was a first born child.
In the report published in the British Medical Journal online Vikanes cautioned that environmental issues and shared lifestyles could not be excluded, and the effects of body mass index (BMI), diet, and smoking may also be contributing factors since they often pass down the generations. She said the findings could help health care personnel to care for women with a family history of hyperemesis gravidarum.
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More information: Recurrence of hyperemesis gravidarum across generations: population based cohort study, BMJ 2010;340:c2050. doi:10.1136/bmj.c2050