Pregnancy complications are known to affect infant health, and in severe situations the child may die during delivery or shortly thereafter, or it may be born with serious handicaps. Sometimes pregnancy complications will also influence maternal health. In Europe, and especially the Nordic countries, few maternal deaths are observed in connection to delivery or in the first weeks after. However, several studies from the US report of increasing early maternal mortality. The WHO definition of maternal mortality is death within the first 42 days after delivery, while studies from the US include maternal deaths for the first year after delivery. We have recently submitted a paper using Norwegian data, covering more than 50 years of population based birth records. In our country, these first year maternal deaths are on its lowest during the last 10 years, opposite to the US trend.
However, there is another aspect of maternal death in relation to pregnancies. Especially during the last 20 years, studies have shown that women who had complications during pregnancies die earlier than other women, mostly due to cardiovascular causes (CVD). The most frequent complications are hypertensive disorders (especially preeclampsia), placental abruption, gestational diabetes, preterm delivery, stillbirths and growth retarded children. One of the first review papers on preeclampsia and its relation to cardiovascular disease (stroke and/or ischaemic heart disease) later in life was published by Bellamy et al (BMJ, 2007), although Chesley published a paper on this relation 40 years earlier (1976). Since this BMJ paper, there has been a long series of reviews covering the major complications. Most estimates vary between 1.5 and 2.5 (Hazard Ratios (HR) of deaths) both linked to stroke and ischaemic heart disease.
When focusing on recurrent events, I discovered another group of mothers with complications, a relatively small group of mothers, “one child mothers”. Also this group have had little attention. In Norway, 85% of women have two or more pregnancies. This means that 15% of women have only one lifetime pregnancy. We found that this group of mothers had a higher risk for early death, even without one of the complications listed above.
We chose to study preeclampsia. Also, we added the effects of preterm delivery. The effects were much stronger than we had expected. We also found that ‘one-child’ interacted strongly with the occurrence of preterm-preeclampsia onto early maternal CVD deaths. Preterm preeclampsia for one-child mothers gave us an almost 10-fold CVD risk (hazard ratio; HR=9.4) while on the other hand, term preeclampsia in women with two or more lifetime pregnancies provided a much lower risk (HR=1.5). Our study was published in BMJ in 2010. We found that ‘one-child’ interacted strongly with the occurrence of preterm-preeclampsia onto early maternal CVD deaths. We learned from that study that there are huge heterogeneities in CVD risk way beyond what is stated by the many review papers.
