The development and evolution of research hotspots can be obtained by sorting out the clusters of keywords and burst keywords from CiteSpace operation. The aforementioned clusters can be generally divided into three aspects including PA patterns (#0 physical activity, #8 muscle strengthening), lifestyle, risk factors (#3 sitting time, #4 preterm birth, #6 risk factors), and pregnancy complications (#1 gestational diabetes, #2 oxidative stress, #5 insulin sensitivity). The noticeable keywords with the strongest burst in 2010–2015 included activity pattern, exercise, maternal exercise, endurance exercise, and leisure-time PA, which indicated that activity pattern was the prior research focus. In 2016–2022, the burst keywords of GDM and maternal obesity demonstrated that the research focus during this period had gradually shifted to the improvement of pregnant complications. Moreover, keywords such as lifestyle intervention, sedentary behavior, lifestyle, and prenatal care, with the strongest burst, entailed that the effect of lifestyle on pregnancy was also a research hotspot.

The amelioration of pregnancy complications by PA has been another research hotspot in recent years. “Risk factor” is a high-frequency keyword, with 321 citations and one main cluster, which mainly addressed GDM, gestational weight gain, anxiety, and depression, lower back pain, pelvic girdle pain, fetal responses, and birth weight. GDM has emerged as a highly cited keyword, a strong burst keyword, and a main cluster, showing it as a primary research hotspot. While weight, maternal obesity, and weight loss are all strong burst keywords, as well indicating that gestational weight gain and weight control are both essential research spots. Globally, half of all the females who are at childbearing age are overweight or obese [16], which potentially will trigger excessive gestational weight gain and increases the risk of developing GDM [16,17,18]. GDM is related to a higher incidence of negative pregnancy outcomes and a long-term risk of childhood obesity and type-2 diabetes in both mother and the infant. Nevertheless, excessive gestational weight gain, GDM, as well as the possible complications of obesity during pregnancy could be minimized with PA [18]. The 2018 PA Guidelines Advisory Committee reported a significant inverse relationship between PA and weight gain, risk of gestational diabetes mellitus or preeclampsia, and symptoms of depression or anxiety [13]. A former study suggested that for pregnant women with GDM, any form of PA that is sufficiently intense and prolonged can be beneficial [19]. A meta-analysis demonstrated that participating in prenatal PA reduces the risk of having GDM by 40% [20]. Anxiety and depression can be commonly observed in pregnant women, which may have a negative impact on the health of both the mother and fetus [21,22]. An incidence of 16% of depressive symptoms, 5% of severe depressive symptoms, and 27% of lifted prenatal anxiety was demonstrated in previous studies [22]. PA has been proven able to play a role as a psychotherapeutic to attenuate depression and anxiety by changing neurotransmitter and hormone levels that are linked to depression and enhancing the encouragement of self-efficacy [23,24,25,26]. Lower back pain and pelvic pain happened frequently in two-thirds of pregnant women as pregnancy advances [27]. A meta-analysis illustrated that multiple types of exercise obtain functions ameliorating back pain and pelvic pain involving aerobic exercise, muscle strengthening exercise, flexibility exercise, and stretching exercise [28]. Fetal responses and birth weight have been addressed a lot with the citations of health and preterm birth. On one hand, researchers have illustrated that fetuses give response during or after exercise as light-to-moderate increases in fetal heart rate of 10–30 beats per minute over the baseline [29,30]. On the other hand, despite this, women who tend to exercise vigorously during the third trimester have a greater possibility to deliver infants with weights 200–400 g less than those who do not [31,32]. Yet neither has observed an increased risk of fetal growth or preterm birth; rigorous exercise has been proven safe for fetuses and mothers in the second trimester, whether they are physically active or not [29,30,31,32].

“PA,” “exercise,” and “aerobic” are all highly cited keywords with citations of 365, 151 and 126, whilst “activity pattern,” “exercise, maternal exercise,” and “endurance exercise” are all strong burst keywords. Moreover, #0 physical activity and #8 muscle strengthening are both prevalent main clusters. Aerobic exercise was used the most widely during pregnancy [33]. Regular aerobic exercise during pregnancy has been proven efficient to improve or maintain physical fitness. Specifically, simple activities such as walking, cycling, swimming, or other modified activities like yoga, are all encouraged for pregnant women to regularly perform in every trimester [34,35]. Current recommendations state that healthy pregnant women should engage in 150 min or more of moderate-intensity aerobic activity each week [36,37]. This exercise should be carried out over the duration of the week and modified as necessary for health. For instance, pregnant women who engaged in aerobic exercise for 30–60 min per day, 2–7 times per week, were observed having a significantly lower risk of prenatal hypertensive disorders, gestational hypertension, and cesarean delivery than the sedentary group [38].

Guidelines reported that healthy pregnant women who are very active, or frequently engage in vigorous-intensity aerobic activity can continue the intensive training [33,36], such as strength training, or high-intensity interval training (HIIT). Research indicated that resistance exercise can achieve perceived physical and mental vigor, attenuate feelings of fatigue and low energy [39]. The strengthening of abdominal and back muscles could minimize the risk of lower back pain [34]. Noticeably, a quick rise in blood pressure and intra-abdominal pressure is triggered by heavy strength training during pregnancy, which may momentarily reduce blood flow to the fetus. However, resistance exercise with a modest to moderate load had no negative consequences during pregnancy [40]. Resistance exercise with elastic belts for 2–3 repetitive sets of movements, or through self-muscle exercises that involve upper and lower limbs for 2–3 sets of 12–24 repetitions, would fit well in pregnancy [41]. HIIT is the second most popular kind of exercise in the European fitness trends [42]. The intensity of training and interval section was monitored and measured by maximal heart rate or Borg’s rate of perceived exertion scale [43], meanwhile the ratio of exercise and rest time depends on individual capabilities, training progression, and pregnancy stage [44]. With regards to obstetric outcomes, HIIT programs were proven to be safe and well-accepted by pregnant women regardless of the training components and interval structure [45], even during the third trimester [46]. Nonetheless, the association between health outcomes and different type, timing, or domain of activity patterns cannot be assured due to insufficient research evidence [33].

Generally, PA during pregnancy with moderate intensity is agreed to be basically safe and beneficial for both mother and fetus [47,48,49]. However, exercise with contraindications is outside the purview of what an exercise expert is allowed to do. As official guidelines stated, women with absolute contraindications should be restricted from strenuous exercise. Women with relative contraindications should only participate in moderate-to-vigorous intensity PA with professional advice and obstetric care [37,50,51]. Gynecologists or other obstetric care professionals should thoroughly assess women with medical or obstetric complications before they begin the activities. Both active and inactive healthy women should start prenatal activities [34]. Women who suffered from complicated pregnancies (Gestational diabetes mellitus, high blood pressure, or other complications) also should continue their normal everyday activities and modify their exercise programs with qualified prenatal exercise specialists.

Given that “lifestyle intervention,” “leisure-time PA,” “sedentary behavior,” and “lifestyle” are all strong burst keywords, “sitting time” is one main cluster, and the effect of lifestyle intervention on pregnancy is one of the important research hotspots. Furthermore, “sedentary behavior” and “lifestyle” are also the newest strong burst keywords, which leads the effect of lifestyle intervention on pregnancy to be the research frontier on PA during pregnancy. Previous studies suggested that sedentary behaviour in pregnancy would probably lead to macrosomic infants, gestational weight gain, and hypertensive disorders [52], shorter gestation, and inhibited fetal growth [53]. That changing lifestyle during pregnancy by implementing leisure-time PA has been analyzed and discussed frequently in recent years [54,55,56]. A systematic review clearly showed that healthy expectant mothers can perform mild, moderate, and even vigorous levels of leisure-time PA without running the danger of giving birth prematurely [57]. A great number of previous cohort studies focused on diverse aspects can be found published, which is one of the foremost reasons why the #8 cohort study is presented as one main cluster. In maternal health, a systematic review that included seven cohort studies achieved controversial results, but generally, high-intensity leisure-time PA before and/or during pregnancy, or performing more than 4 h leisure-time PA each week may reduce the risk of pre-eclampsia [56]. A cohort study with 3209 participants suggested that leisure-time PA during both pre-pregnancy and early pregnancy reduced 46% of the risk of GDM compared with inactivity groups during both periods [58]. Meanwhile, another cohort study with 10,038 pregnant women illustrated that sustained low leisure-time PA during pregnancy is associated with excess risk of GDM and overall preterm birth. Moreover, women who increased leisure time PA lowered the rate of GDM. This could indicate that the increase in leisure-time PA in early pregnancy phases may be related to improved pregnancy health [59]. In offspring health, a cohort study proved that sons of women with light and moderate to heavy leisure-time PA had a lower risk of having a low intelligence score compared with sons of sedentary women [60]. Similarly, a systematic review and meta-analysis of 30 randomized controlled trials and 51 cohort studies supported the promotion of LTPA in pregnancy as a strategy to improve maternal and child health [61]. Furthermore, current cohort study results have also shown positive relationships between leisure-time PA and hyperemesis gravidarum [62], head circumference among male infants [63], birthweight among female infants, and women with normal prepregnancy BMI [63]. Conversely, no association was found between leisure-time PA and adiposity in mid-childhood [64] and intelligence quotient [65].