Physical Activity, Fertility, and Spontaneous Abortion in Danish Couples Trying to Conceive

Infertility, defined as the failure to achieve pregnancy after 12 months of regular unprotected sexual intercourse, and spontaneous abortion (SAB) are significant public health problems, affecting up to 20% of reproductive age couples in the Western World. A large proportion of couples seek fertility treatment, which is not only an economic burden for the society, but also associated with adverse health effects among infertile couples. The causes of both infertility and SAB are multifactorial and identification of modifiable risk factors is an important public health goal.

According to the Danish Health Authority, adults are recommended to be physically active for at least 30 minutes per day, to undertake muscle-strengthening activities on two or more days per week and to reduce sedentary time. The same applies for pregnant women without complications. However, only 15-38% of pregnant women adhere to the recommendations for PA and many women reduce their level of exercise during early pregnancy compared with pre-pregnancy. Yet, maternal health in both the preconception period and during pregnancy is critical to avoid complications during pregnancy and for the long-term health of mother and child.

We therefore aim to investigate the association between PA, fecundability (i.e., the average per-cycle probability of conception), and SAB. An efficient web-based infrastructure to recruit, follow, and collect comprehensive data has already been developed. In the ongoing prospective cohort study, SnartForældre.dk (SF), we investigate fecundability and SAB according to demographic, behavioral, environmental, and medical factors and have enrolled more than 10,000 women and 1,700 of their male partners who are trying to conceive without fertility treatment.

In the present SF sub-study, SnartForældre.dk/Aktivitet, we aim to conduct a two-armed randomized controlled trial with 500 women included, to investigate the effectiveness of receiving motivational counseling on physical activity (PA) among women trying to conceive and during the first trimester of the pregnancy if they conceive. We will further investigate whether PA is associated with fecundability, spontaneous abortion (SAB) and other birth outcomes, i.e., gestational diabetes, preeclampsia, and birth weight. As we will be able to combine self-reported data, objectively measured data on PA, and high-quality Danish registry data, we have a unique possibility to evaluate the impact of PA on fecundability and SAB, as well as other pregnancy complications and birth outcomes, in a way that is hardly possible in any other country.

The study will provide important knowledge that will be of interest for the scientific world, health professionals, and for couples who suffer from infertility or experience SABs.