Twin Pregnancies: women’s health and reproduction

In Norway, the proportion of twin pregnancies has varied between one and two percent of all pregnancies in the period 1970-2020. Twin pregnancies have generally been less studied compared to singletons. Using population-based national registry data we were able to study twin pregnancies for better understanding on how their reproductive and obstetric history impact long-term maternal mortality, offspring birthweight in subsequent pregnancy and intergenerational association of adverse pregnancy outcomes. 

Linking data from Medical Birth Registry of Norway with Norwegian Cause of death registry, we found that women with only one lifetime twin or singleton pregnancy had similar risk of cardiovascular mortality before 70 years. Women who started their reproduction with a first twin pregnancy and continued to have more children did not have an increased risk of cardiovascular disease mortality compared with women with three singleton pregnancies. We further explored birthweight in the next singleton pregnancy after a previous twin pregnancy. Birthweight of babies in the second pregnancy is often greater than the first singleton babies. Our study showed that women with a first twin pregnancy have singletons in the next pregnancy of similar birthweight to women with a first singleton pregnancy. Our findings indicate that the increased physiological and mechanical burden resulting from a twin pregnancy do not explain the general parity effect on the birthweight of first and second singleton births. Despite the fact that twin-born women more often are exposed to adverse pregnancy outcomes in utero, the risk of preeclampsia, preterm delivery and perinatal loss in twin-born women was not increased in their own pregnancies compared with singleton-born women.

From our results we conclude that, despite twin pregnancies being clinically more complicated and challenging, women with twin pregnancies did not have increased long-term cardiovascular disease mortality compared to women with singleton pregnancies. Women with first twin- or singleton pregnancies had offspring with comparable birthweight in the next pregnancy. Also, women born as twin did not have increased risk of adverse pregnancy outcomes in their own pregnancies.

Personalia
Prativa Basnet grew up in Nepal. She has a master’s degree in Public Health from the University of Eastern Finland (2019). The PhD-thesis has been carried out at the Department of Global Public Health and Primary Care at the University of Bergen. The main supervisor was associate professor Liv Grimstvedt Kvalvik. Co-supervisors were professor Rolv Skjærven, associate professor Linn Marie Sørbye and professor Nils-Halvdan Morken.