Reduction in activity by the mother – pelvic rest, limited work, bed rest – may be recommended although there is no evidence it is useful with some concerns it is harmful. Increasing medical care by more frequent visits and more education has not been shown to reduce preterm birth rates. Use of nutritional supplements such as omega-3 polyunsaturated fatty acids is based on the observation that populations who have a high intake of such agents are at low risk for preterm birth, presumably as these agents inhibit production of proinflammatory cytokines. A randomized trial showed a significant decline in preterm birth rates, and further studies are in the making.

A number of agents have been studied for the secondary prevention of indicated preterm birth. Trials using low-dose aspirin, fish oil, vitamin C and E, and calcium to reduce preeclampsia demonstrated some reduction in preterm birth only when low-dose aspirin was used. Interestingly, even if agents such as calcium or antioxidants were able to reduce preeclampsia, a resulting decrease in preterm birth was not observed.

Bed rest has not been found to improve outcomes and therefore is not typically recommended.

Mothers whose fetus is diagnosed with intrauterine growth restriction by ultrasound can use management strategies based on monitoring and delivery methods. One of these monitoring techniques is an umbilical artery Doppler. This method has been shown to decrease risk of morbidity and mortality before and after parturition among IUGR patients.

Time of delivery is also a management strategy and is based on parameters collected from the umbilical artery doppler. Some of these include: pulsatility index, resistance index, and end-diastolic velocities, which are measurements of the fetal circulation.

90 percent of babies born SGA catch up in growth by the age of 2. However, all SGA babies should be watched for signs of Failure-to-Thrive (FTT), hypoglycemia and other conditions common to SGA babies (see below). Hypoglycemia is common in asymmetrical SGA babies because their larger brains burn calories at a faster rate than their usually limited fat stores hold. Hypoglycemia is treated by frequent feedings and/or additions of cornstarch-based products (such as Duocal powder) to the feedings.

For the 10 percent of those that are SGA without catchup growth by the age of 2, an endocrinologist should be consulted. Some cases warrant growth hormone therapy (GHT).

There are some common conditions and disorders found in many that are SGA (and especially those that are SGA without catchup growth by age 2). They should be treated by the appropriate specialist:

- Gastroenterologist - for gastrointestinal issues such as: reflux (GERD) and/or delayed gastric emptying (DGE)

- Dietitian - to address caloric deficits. Dietitians are usually brought in for cases that include FTT. Also, according to the theory of thrifty phenotype, causes of growth restriction also trigger epigenetic responses in the fetus that are otherwise activated in times of chronic food shortage. If the offspring actually develops in an environment rich in food it may be more prone to metabolic disorders, such as obesity and type II diabetes.

- Speech Language Pathologist (SLP) or Occupational Therapist (OT) - for feeding issues. OTs may also treat sensory issues

- Behaviorist - for feeding issues, a behavioral approach may also be used, but usually for older children (over 2)

- Allergist - to diagnose or rule out food allergies (not necessarily more common in those SGA than the normal population)

- Ear, Nose and Throat doctor (ENT) - to diagnose enlarged adenoids or tonsils (not necessarily more common in those SGA than the normal population)

For IUGR (during pregnancy), possible treatments include the early induction of labor, though this is only done if the condition has been diagnosed and seen as a risk to the health of the fetus.

Low birthweight, pre-term birth and pre-eclampsia have been associated with maternal periodontitis exposure. But the strength of the observed associations is inconsistent and vary according to the population studied, the means of periodontal assessment and the periodontal disease classification employed. However the best is that the risk of low birth weight can be reduced with very simple therapy. Treatment of periodontal disease during gestation period is safe and reduction in inflammatory burden reduces the risk of preterm birth as well as low birth weight.

While active maternal tobacco smoking has well established adverse perinatal outcomes such as LBW, that mothers who smoke during pregnancy are twice as likely to give birth to low-birth weight infants. Review on the effects of passive maternal smoking, also called environmental tobacco exposure (ETS), demonstrated that increased risks of infants with LBW were more likely to be expected in ETS-exposed mothers.

Regarding environmental toxins in pregnancy, elevated blood lead levels in pregnant women, even those well below 10 ug/dL can cause miscarriage, premature birth, and LBW in the offspring. With 10 ug/dL as the Centers for Disease Control and Prevention's “level of concern”, this cut-off value really needs to arise more attentions and implementations in the future.

The combustion products of solid fuel in developing countries can cause many adverse health issues in people. Because a majority of pregnant women in developing countries, where rate of LBW is high, are heavily exposed to indoor air pollution, increased relative risk translates into substantial population attributable risk of 21% of LBW.

One environmental exposure which has been found to increase the risk of low birth weight is particulate matter, a component of ambient air pollution. Because particulate matter is composed of extremely small particles, even nonvisible levels can be inhaled and present harm to the fetus. Particulate matter exposure can cause inflammation, oxidative stress, endocrine disruption, and impaired oxygen transport access to the placenta, all of which are mechanisms for heightening the risk of low birth weight. To reduce exposure to particulate matter, pregnant women can monitor the EPA’s Air Quality Index and take personal precautionary measures such as reducing outdoor activity on low quality days, avoiding high-traffic roads/intersections, and/or wearing personal protective equipment (i.e., facial mask of industrial design). Indoor exposure to particulate matter can also be reduced through adequate ventilation, as well as use of clean heating and cooking methods.

A correlation between maternal exposure to CO and low birth weight has been reported that the effect on birth weight of increased ambient CO was as large as the effect of the mother smoking a pack of cigarettes per day during pregnancy.

It has been revealed that adverse reproductive effects (e.g., risk for LBW) were correlated with maternal exposure to air pollution combustion emissions in Eastern Europe and North America.

Mercury is a known toxic heavy metal that can harm fetal growth and health, and there has been evidence showing that exposure to mercury (via consumption of large oily fish) during pregnancy may be related to higher risks of LBW in the offspring.

It was revealed that, exposure of pregnant women to airplane noise was found to be associated with low birth weight. Aircraft noise exposure caused adverse effects on fetal growth leading to low birth weight and preterm infants.

In sheep, intrauterine growth restriction can be caused by heat stress in early to mid pregnancy. The effect is attributed to reduced placental development causing reduced fetal growth. Hormonal effects appear implicated in the reduced placental development. Although early reduction of placental development is not accompanied by concurrent reduction of fetal growth; it tends to limit fetal growth later in gestation. Normally, ovine placental mass increases until about day 70 of gestation, but high demand on the placenta for fetal growth occurs later. (For example, research results suggest that a normal average singleton Suffolk x Targhee sheep fetus has a mass of about 0.15 kg at day 70, and growth rates of about 31 g/day at day 80, 129 g/day at day 120 and 199 g/day at day 140 of gestation, reaching a mass of about 6.21 kg at day 140, a few days before parturition.)

In adolescent ewes (i.e. ewe hoggets), overfeeding during pregnancy can also cause intrauterine growth restriction, by altering nutrient partitioning between dam and conceptus. Fetal growth restriction in adolescent ewes overnourished during early to mid pregnancy is not avoided by switching to lower nutrient intake after day 90 of gestation; whereas such switching at day 50 does result in greater placental growth and enhanced pregnancy outcome. Practical implications include the importance of estimating a threshold for "overnutrition" in management of pregnant ewe hoggets. In a study of Romney and Coopworth ewe hoggets bred to Perendale rams, feeding to approximate a conceptus-free live mass gain of 0.15 kg/day (i.e. in addition to conceptus mass), commencing 13 days after the midpoint of a synchronized breeding period, yielded no reduction in lamb birth mass, where compared with feeding treatments yielding conceptus-free live mass gains of about 0 and 0.075 kg/day.

In both of the above models of IUGR in sheep, the absolute magnitude of uterine blood flow is reduced. Evidence of substantial reduction of placental glucose transport capacity has been observed in pregnant ewes that had been heat-stressed during placental development.

Small for gestational age (SGA) newborns are those who are smaller in size than normal for the gestational age, most commonly defined as a weight below the 10th percentile for the gestational age.

The non-specific effects of vaccines can be boosted or diminished when other immunomodulating health interventions such as other vaccines, or vitamins, are provided.

The live attenuated BCG vaccine developed against tuberculosis has been shown to have strong beneficial effects on the ability to combat non-tuberculosis infections.

Several studies have suggested that BCG vaccination may reduce atopy, particularly when given early in life. Furthermore, in multiple observational studies BCG vaccination has been shown to provide beneficial effects on overall mortality. These observations encouraged randomised controlled trials to examine BCG vaccination's beneficial non-specific effects on overall health. Since BCG vaccination is recommended to be given at birth in countries that have a high incidence of tuberculosis it would have been unethical to randomize children into 'BCG' vs. 'no BCG' groups. However, many low-income countries delay BCG vaccination for low-birth-weight (LBW) infants; this offered the opportunity to directly test the effect of BCG on overall mortality.

In the first two randomised controlled trials receipt of BCG+OPV at birth vs. OPV only ('delayed BCG') was associated with strong reductions in neonatal mortality; these effects were seen as early as 3 days after vaccination. BCG protected against sepsis as well as respiratory infections.

Among BCG vaccinated children, those who develop a BCG scar or a positive skin test (TST) are less likely to develop sepsis and exhibit an overall reduction in child mortality of around 50%.

In a recent WHO-commissioned review based on five clinical trials and nine observational studies, it was concluded that "the results indicated a beneficial effect of BCG on overall mortality in the first 6–12 months of life. Relevant follow-up in some of the trials was short, and all of the observational studies were regarded as being at risk of bias, so the confidence in the findings was rated as very low according to the GRADE criteria and "There was a suggestion that BCG vaccination may be more beneficial the earlier it is given". Furthermore, "estimated effects are in the region of a halving of mortality risk" and "any effect of BCG vaccine on all-cause mortality is not likely to be attributable to any great extent to fewer deaths from tuberculosis (i.e. to a specific effect of BCG vaccine against tuberculosis)". Based on the evidence, the WHO's Strategic Group of Experts on Immunization concluded that "the non-specific effects on all-cause mortality warrant further research".