Having babies

Exercise before and during pregnancy  are fertile grounds for uncertainty and the growth of myths. After all, even the labels given to the pregnant state can be discouraging – ie “being in a delicate condition”. However it has long been recognised that physical activity may be a “good thing” as a preparation for pregnancy and labour – for instance Biblical writers noticed that Hebrew slave women gave birth more easily than their sedentary Egyptian mistresses!

Exercise and miscarriages

Miscarriages are extremely common in the first three months of pregnancy – about one in five of apparently normal pregnancies thus. Fear of miscarrying sometimes leads to a reluctance to be too active in early pregnancy – but there is no evidence that there is any association – miscarriages are no more common in those who exercise than those who do not, however strenuous that may be.

Exercise and fertility

Girls: Physical activity within the DoH-recommended levels normally has no effect on fertility and the chances of becoming pregnant. There are circumstances when exercise can increase the chance of becoming pregnant, particularly in obese women who use exercise to lose weight. However those who take excessive amounts of exercise may experience a fall in female hormone levels with loss of periods and difficulty in getting pregnant. This is particularly so in women with exercise addiction, most commonly found in runners and compulsive over-users of the gym.

Boys:  Regular exercise has been shown to improve sperm “quality” but studies of the frequency of pregnancy achieved by sperm donors who do or do not take vigorous exercise have been variable. However a meta-analysis involving more than 1,600 men found that high levels of physical exercise are significantly associated with higher sperm concentration, increased sperm motility (how fast they swim), total sperm count and normal microscopy appearance. Moreover physical activity had a significant association with live birth rates.

Exercise during pregnancy

Taking regular exercise has no adverse effects on pregnancy. Nearly all sources of advice on the subject encourage physical activity for pregnant women at the same level recommended for all adults. There seems to be no ill effects from vigorous exercise. The usual advice is that women should continue with their usual level of exertion and, if this is inadequate, increase to at least the level of DoH recommendation. This is particularly important for overweight individuals for whom increased activity can reduce the rate of undesirable weight gain during pregnancy.

A controlled trial of mixed aerobic and strength training in 160 pregnant women found that the exercise group experienced a longer first stage (pre-pushing) but a shorter second stage (pushing) of labour. The exercise group also had somewhat heavier placentas and babies. There was no difference in the mode of delivery.

A large systematic study of the effect of exercise in 2500 women randomised to either normal activity or a 30 to 60 minute exercise programme found hypertension (high blood pressure) in 5.9% of the treated group compared to 8.5% in the sedentary group – a 70% reduction. The significance of this is that hypertension in pregnancy increases the risk of pre-eclampsia which can be a threat to the health and sometimes the life of mother and child.  This was confirmed by another analysis which showed a 25% decrease in pre-eclampsia for women taking part in exercise programmes during pregnancy.

Another common condition of pregnancy is “gestational” diabetes (GDM) – that is Type 2 Diabetes (T2DM) during pregnancy, an increasingly common condition. Currently the rate in the UK is about 5% and results in larger babies, more difficulties in labour and higher rates of stillbirth. 50% of women with GDM go on to develop T2DM later in life. Regular moderate exercise roughly halves the rate of GDM –  more vigorous exercise reduces it by about 75%.

Other benefits include reduction in hyperemesis (excessive vomiting), pelvic pain and preterm birth – prematurity.

Contra-indications

The main contra-indications to exercise in pregnancy are mainly matters of common sense – vaginal bleeding, placenta-previa ( a condition in which the placenta is very low in the uterus, often leading to vaginal bleeding) multiple pregnancy of 3 or more offspring, and uncontrolled high blood pressure.

Recommendations

The overall global physical inactivity prevalence for women is about 30%. During pregnancy, the prevalence of physical inactivity tends to be higher than the general female population because pregnant women tend to reduce their physical activity once they become pregnant. In some populations as many as 75.0% are classed as sedentary. The general advice is the same for them all – try to be as active as is recommended and if possible do more!