Pregnancy usually brings joy to many families keen on having children. Whereas it can occur much faster or easily for most women, some usually struggle to conceive.
And when pregnant, women may end up losing multiple pregnancies for reasons unknown to them. One of the least appreciated reason is physical exercises
A new study published in the Journal of Fertility and Sterility notes that women with a history of miscarriage should refrain from engaging in higher levels of physical activity while planning to conceive.
Findings of the research revealed that strenuous exercises might cause early pregnancy losses (within two weeks after conception).
Based on assessments from the University of Massachusetts Amherst's researchers that conducted the study, high intensity exercises impede the implantation of an embryo (fertilised egg) on the lining of the uterus.
This usually happens between six to 12 days after conception, before most women even realise that they are pregnant.
According to the research, the risk of miscarriage following strenuous exercises seems to increase before the embryo implantation takes places.
Indeed, the study found that there was roughly a two-fold higher risk of very early pregnancy loss among women who were highly active compared to those that were less.
The researchers noted that this kind of miscarriage could be difficult to detect because it may occur before a woman is even aware that she is pregnant.
Noticeable signs of pregnancy are usually experienced by women weeks after conception has taken place.
Yet the implantation process, which is affected by strenuous exercises, happens much earlier – within days – after conception.
"Determination of these very early pregnancy failures requires lab tests and daily specimen collection to identify pregnancies and losses. Few studies are able to do this," noted Brian Whitcomb, a senior author of the study and associate professor of epidemiology at the University of Massachusetts Amherst's School of Public Health and Health Sciences.
He stated: "We were able to address an interesting gap. There has been conflicting evidence of whether physical activity can have negative, beneficial or no effects on pregnancy."
During the study, the researchers analysed data of women between 18 and 40 years old who had experienced one or two pregnancy losses and were trying to conceive from 2007 to 2011.
They looked at the impact of physical activity on their pregnancy outcomes.
The study participants used home pregnancy tests to determine whether they were expectant. In addition, the researchers also relied on laboratory tests used to confirm pregnancy in its very early stages.
These tests usually assess levels of a hormone known as Human Chorionic Gonadotropin (HCG), which normally rises during early pregnancy.
Among the 785 women who became pregnant, 188 (23.9 percent) experienced miscarriages, including 55 that had very early pregnancy losses which were detected only from HCG testing.
"We're trying to provide good, evidence-based information for women who are pregnant and want to know what to do and also for clinicians who are giving guidance and advice to their patients," said Whitcomb.
Based on the results of the study, the researchers suggest that women who have lost a pregnancy may want to avoid high-strain activity in the earliest stage of a subsequent pregnancy, or around the time of trying to become pregnant.
"For women who are experiencing difficulty conceiving, our results are consistent with prior work that has also shown that high exercise strain during the implantation period may be related to increased risk of loss," Whitcomb said.
Aside from women with a history of miscarriages, exercises are also not recommended for mother with the following conditions: bleeding or spotting, low laying placenta, weak cervix, previous premature births or a history of early labour.
On the contrary, health experts note that moderate physical activity is recommended for women with normal pregnancies.
They note that exercises are safe to perform during pregnancy as long as mothers exercise with caution and do not overdo it.
Regular exercise during pregnancy can improve posture and decrease common challenges such as backaches and fatigue.
There is also evidence that physical activity may prevent gestational diabetes (diabetes that develops during pregnancy), relieve stress, and build more stamina needed for labour and delivery.
Examples of recommended moderate exercises during pregnancy include swimming, brisk walking, indoor stationary cycling and low-impact aerobics (taught by a certified aerobics instructor).