A number of studies have shown that tobacco use is a significant factor in miscarriages among pregnant smokers, and that it contributes to a number of other threats to the health of the fetus. Smoking and pregnancy, combined, cause twice the risk of premature rupture of membranes, placental abruption and placenta previa. Also, it causes 30% higher odds of the baby being born prematurely.

Prenatal cocaine exposure is associated with, for example, premature birth, birth defects and attention deficit disorder.

A recent study on cocaine in Prenatal Drug Exposure(2008) explores how the differences between children who were exposed to drugs prenatal and those with non-drug prenatal exposure differ at the age of five.

Many of the side effects from the children who were exposed to the recreational drug being cocaine had side effects including the following; lack in school readiness, slower impulse control and lack in visual attention.

Intrauterine exposure to environmental toxins in pregnancy has the potential to cause adverse effects on the development of the embryo/fetus and to cause pregnancy complications. Air pollution has been associated with low birth weight infants. Conditions of particular severity in pregnancy include mercury poisoning and lead poisoning. To minimize exposure to environmental toxins, the "American College of Nurse-Midwives" recommends: checking whether the home has lead paint, washing all fresh fruits and vegetables thoroughly and buying organic produce, and avoiding cleaning products labeled "toxic" or any product with a warning on the label.

Pregnant women can also be exposed to toxins in the workplace, including airborne particles. The effects of wearing N95 filtering facepiece respirators are similar for pregnant women as non-pregnant women, and wearing a respirator for one hour does not affect the fetal heart rate.

The data presented is for comparative and illustrative purposes only, and may have been superseded by updated data.

The use of recreational drugs in pregnancy can cause various pregnancy complications.

- Ethanol during pregnancy can cause fetal alcohol syndrome and fetal alcohol spectrum disorder. Studies have shown that light to moderate drinking during pregnancy might not pose a risk to the fetus, although no amount of alcohol during pregnancy can be guaranteed to be absolutely safe.

- Tobacco smoking during pregnancy can cause a wide range of behavioral, neurological, and physical difficulties. Smoking during pregnancy causes twice the risk of premature rupture of membranes, placental abruption and placenta previa. Smoking is associated with 30% higher odds of preterm birth.

- Prenatal cocaine exposure is associated with premature birth, birth defects and attention deficit disorder.

- Prenatal methamphetamine exposure can cause premature birth and congenital abnormalities. Short-term neonatal outcomes show small deficits in infant neurobehavioral function and growth restriction. Long-term effects in terms of impaired brain development may also be caused by methamphetamine use.

- Cannabis in pregnancy has been shown to be teratogenic in large doses in animals, but has not shown any teratogenic effects in humans.

The pregnancy category of a medication is an assessment of the risk of fetal injury due to the pharmaceutical, if it is used as directed by the mother during pregnancy. It does "not" include any risks conferred by pharmaceutical agents or their metabolites in breast milk.

Every drug has specific information listed in its product literature. The British National Formulary used to provide a table of drugs to be avoided or used with caution in pregnancy, and did so using a limited number of key phrases, but now Appendix 4 (which was the Pregnancy table) has been removed. Appendix 4 is now titled "Intravenous Additives". However, information that was previously available in the former Appendix 4 (pregnancy) and Appendix 5 (breast feeding) is now available in the individual drug monographs.

Some women have a greater risk of developing hypertension during pregnancy. These are:

- Women with chronic hypertension (high blood pressure before becoming pregnant).

- Women who developed high blood pressure or preeclampsia during a previous pregnancy, especially if these conditions occurred early in the pregnancy.

- Women who are obese prior to pregnancy.

- Pregnant women under the age of 20 or over the age of 40.

- Women who are pregnant with more than one baby.

- Women with diabetes, kidney disease, rheumatoid arthritis, lupus, or scleroderma.

A longitudinal study done on prenatal stress and gender roles showed that prenatal stress only plays a small part in the gender roles the offspring takes on and mentions it has more to do with older siblings, maternal use of alcohol and/or tobacco, maternal education, and the observance or teaching of “traditional sex roles” from the parents.

Hormonal and other changes in pregnancy affect physical performance. In the first three months it is known that a woman’s body produces a natural surplus of red blood cells, which are well supplied with oxygen-carrying hemoglobin, in order to support the growing fetus. A study of athletes before and after pregnancy by Professor James Pivarnik at the Human Energy Research laboratory in Michigan State University has found there is a 60 per cent increase in blood volume and that this could improve the body’s ability to carry oxygen to muscles by up to 30 percent. This would have obvious positive effects on aerobic capacity. Other potential advantages are obtained from the surge in hormones that pregnancy induces, predominantly progesterone and estrogen, but also testosterone, which could increase muscle strength. Increases in hormones like relaxin, which loosens the hip joints to prepare for childbirth, may have a performance-enhancing effect on joint mobility.

Several world records have been set by female athletes shortly after giving birth to their first child. This is accepted as a natural and unintended event.

Prenatal stress (or prenatal maternal stress) is exposure of an expectant mother to stress, which can be caused by stressful life events or by environmental hardships. The resulting changes to the mother's hormonal and immune system may harm the fetus's (and after birth, the infant's) immune function and brain development.

Prenatal stress is shown to have several affects in fetal brain development. In the hippocampus of adult male rats, prenatal stress has shown to decrease the rate of proliferation and cell death in the hypothalamus-pituitary axis. Prenatal stressed animals have prolonged corticosterone response. Removing the adrenal glands of the mother eliminates the effect of the pup's corticosterone response. Supplementing the adrenalectamized mother with corticosterone, rescued the hypothalamic-pituitary-axis response to maternal stress for prenatally stressed offspring. Prenatal stress caused high glucocorticoids, which in turn affects the hypothalamic-pituitary-axis negative feedback.

A study by García-Cáceres et al. showed that prenatal stress decreases cell turnover and proliferation in the hypothalamus of adult rats, which reduces structural plasticity and reduces the response to stress in adulthood. This study also showed that when prenatally stressed rats were stressed in adulthood the females showed an increase in corticotropin-releasing hormone suggesting it to be an up-regulation in the hypothalamic-pituitary adrenal axis. Males showed no elevation of corticosterone levels. Increase in adrenocorticotropic hormone with no effect of adult stress and a decrease in the corticotropin-releasing hormone mRNA in the hypothalamus showed a down-regulation. The author concludes that this makes prenatally stressed females less reactive to later life stressors than males.

Although many pregnant women with high blood pressure have healthy babies without serious problems, high blood pressure can be dangerous for both the mother and baby. Women with pre-existing, or chronic, high blood pressure are more likely to have certain complications during pregnancy than those with normal blood pressure. However, some women develop high blood pressure while they are pregnant (often called gestational hypertension).

Chronic poorly-controlled high blood pressure before and during pregnancy puts a pregnant woman and her baby at risk for problems. It is associated with an increased risk for maternal complications such as preeclampsia, placental abruption (when the placenta separates from the wall of the uterus), and gestational diabetes. These women also face a higher risk for poor birth outcomes such as preterm delivery, having an infant small for his/her gestational age, and infant death.

Morning sickness may be an evolved trait that protects the baby against toxins ingested by the mother. Evidence in support of this theory includes:

- Morning sickness is very common among pregnant women, which argues in favor of its being a functional adaptation and against the idea that it is a pathology.

- Fetal vulnerability to toxins peaks at around 3 months, which is also the time of peak susceptibility to morning sickness.

- There is a good correlation between toxin concentrations in foods, and the tastes and odors that cause revulsion.

Women who have "no" morning sickness are more likely to miscarry. This may be because such women are more likely to ingest substances that are harmful to the fetus.

In addition to protecting the fetus, morning sickness may also protect the mother. A pregnant woman's immune system is suppressed during pregnancy, presumably to reduce the chances of rejecting tissues of her own offspring. Because of this, animal products containing parasites and harmful bacteria can be especially dangerous to pregnant women. There is evidence that morning sickness is often triggered by animal products including meat and fish.

If morning sickness is a defense mechanism against the ingestion of toxins, the prescribing of anti-nausea medication to pregnant women may have the undesired side effect of causing birth defects or miscarriages by encouraging harmful dietary choices.

Abortion doping refers to the rumoured practice of purposely inducing pregnancy for athletic performance-enhancing benefits, then aborting the pregnancy.

Most Rh disease can be prevented by treating the mother during pregnancy or promptly (within 72 hours) after childbirth. The mother has an intramuscular injection of anti-Rh antibodies (Rho(D) immune globulin). This is done so that the fetal rhesus D positive erythrocytes are destroyed before the immune system of the mother can discover them and become sensitized. This is passive immunity and the effect of the immunity will wear off after about 4 to 6 weeks (or longer depending on injected dose) as the anti-Rh antibodies gradually decline to zero in the maternal blood.

It is part of modern antenatal care to give all rhesus D negative pregnant women an anti-RhD IgG immunoglobulin injection at about 28 weeks gestation (with or without a booster at 34 weeks gestation). This reduces the effect of the vast majority of sensitizing events which mostly occur after 28 weeks gestation. Giving Anti-D to all Rhesus negative pregnant women can mean giving it to mothers who do not need it (because her baby is Rhesus negative or their blood did not mix). Many countries routinely give Anti-D to Rhesus D negative women in pregnancy. In other countries, stocks of Anti-D can run short or even run out. Before Anti-D is made routine in these countries, stocks should be readily available so that it is available for women who need Anti-D in an emergency situation.

A recent review found research into giving Anti-D to all Rhesus D negative pregnant women is of low quality. However the research did suggest that the risk of the mother producing antibodies to attack Rhesus D positive fetal cells was lower in mothers who had the Anti-D in pregnancy. There were also fewer mothers with a positive kleihauer test (which shows if the mother’s and unborn baby’s blood has mixed).

Anti-RhD immunoglobulin is also given to non-sensitized rhesus negative women immediately (within 72 hours—the sooner the better) after potentially sensitizing events that occur earlier in pregnancy.

The discovery of cell-free DNA in the maternal plasma has allowed for the non-invasive determination of the fetal RHD genotype. In May 2017, the Society for Obstetrics and Gynecology of Canada is now recommending that the optimal management of the D-negative pregnant woman is based on the prediction of the fetal D-blood group by cell-free DNA in maternal plasma with targeted antenatal anti-D prophylaxis. This provides the optimal care for D-negative pregnant women and has been adopted as the standard approach in a growing number of countries around the world. It is no longer considered appropriate to treat all D-negative pregnant women with human plasma derivatives when there are no benefits to her or to the fetus in a substantial percentage of cases.

Eight factors were identified in the same study as universal protective factors that reduced the incidence rate of the secondary disabilities:

- Living in a stable and nurturing home for over 73% of life

- Being diagnosed with FAS before age six

- Never having experienced violence

- Remaining in each living situation for at least 2.8 years

- Experiencing a "good quality home" (meeting 10 or more defined qualities) from age 8 to 12 years old

- Having been found eligible for developmental disability (DD) services

- Having basic needs met for at least 13% of life

- Having a diagnosis of FAS (rather than another FASD condition)

Malbin (2002) has identified the following areas of interests and talents as strengths that often stand out for those with FASD and should be utilized, like any strength, in treatment planning:

- Music, playing instruments, composing, singing, art, spelling, reading, computers, mechanics, woodworking, skilled vocations (welding, electrician, etc.), writing, poetry

- Participation in non-impact sport or physical fitness activities

In 2003, the incidence of Rh(D) sensitization in the United States was 6.8 per 1000 live births; 0.27% of women with an Rh incompatible fetus experience alloimmunization.

For many adopted or adults and children in foster care, records or other reliable sources may not be available for review. Reporting alcohol use during pregnancy can also be stigmatizing to birth mothers, especially if alcohol use is ongoing. In these cases, all diagnostic systems use an unknown prenatal alcohol exposure designation. A diagnosis of FAS is still possible with an unknown exposure level if other key features of FASD are present at clinical levels.

Rh disease (also known as rhesus isoimmunisation, Rh (D) disease, rhesus incompatibility, rhesus disease, RhD hemolytic disease of the newborn, rhesus D hemolytic disease of the newborn or RhD HDN) is a type of hemolytic disease of the newborn (HDN). The disease ranges from mild to severe, and typically occurs only in some second or subsequent pregnancies of Rh negative women where the fetus's father is Rh positive, leading to a Rh+ pregnancy. During birth, the mother may be exposed to the infant's blood, and this causes the development of antibodies, which may affect the health of subsequent Rh+ pregnancies. In mild cases, the fetus may have mild anaemia with reticulocytosis. In moderate or severe cases the fetus may have a more marked anaemia and erythroblastosis fetalis (hemolytic disease of the newborn). When the disease is very severe it may cause hydrops fetalis or stillbirth.

Rh disease is generally preventable by treating the mother during pregnancy or soon after delivery with an intramuscular injection of anti-RhD immunoglobulin (Rho(D) immune globulin). The RhD protein is coded by the RHD gene.

A study of a population of French women from 1670 and 1789 shows that those who married at age 20–24 had 7.0 children on average and 3.7% remained childless. Women who married at age 25–29 years had a mean of 5.7 children and 5.0% remained childless. Women who married at 30–34 years had a mean of 4.0 children and 8.2% remained childless. The average age at last birth in natural fertility populations that have been studied is around 40.

In 1957, a study was done on a large population (American Hutterites) that never used birth control. The investigators measured the relationship between the age of the female partner and fertility. (Infertility rates today are believed to be higher in the general population than for the population in this study from the 1950s.)

This 1957 study found that:

- By age 30, 7% of couples were infertile

- By age 35, 11% of couples were infertile

- By age 40, 33% of couples were infertile

- At age 45, 87% of couples were infertile

The average age of a young woman's first period (menarche) is 12 to 13 (12.5 years in the United States, 12.72 in Canada, 12.9 in the UK) but, in postmenarchal girls, about 80% of the cycles are anovulatory in the first year after menarche, 50% in the third and 10% in the sixth year. A woman's fertility peaks in her early and mid-20s after which it starts to decline. However, the exact estimates of the chances of a woman to conceive after a certain age are not clear, and are subject to debate.

According to the National Institute for Health and Clinical Excellence over 80 out of every 100 women aged under 40 who have regular unprotected sexual intercourse will get pregnant within 1 year of trying. In the second year the percentage rises to over 90%.

According to a 2004 study by Henri Leridon, PhD, an epidemiologist with the French Institute of Health and Medical Research of women trying to get pregnant, without using fertility drugs or in vitro fertilization.

- At age 30

- 75% will have a conception ending in a live birth within one year

- 91% will have a conception ending in a live birth within four years

- At age 35

- 66% will have a conception ending in a live birth within one year

- 84% will have a conception ending in a live birth within four years

- At age 40

- 44% will have a conception ending in a live birth within one year

- 64% will have a conception ending in a live birth within four years

According to a study done on a sample of 782 healthy European couples ages 19–39, fertility starts declining after age 27 and drops at a somewhat greater rate after age 35. The women were divided into four age groups: 19–26, 27–29, 30–34 and 35–39. Statistical analysis showed that the women in the 27–29 age group had significantly less chance on average of becoming pregnant than did the 19- to 26-year-olds. Pregnancy rates did not change notably between the 27–29 age group and the 30–34 age group, but dropped significantly for the 35–39 age group. The age of the male partner had a significant impact on female fertility among the women who had reached their mid-30s, but not among the younger women. However, experts said the new study was too small and there were too many variables which were too difficult to sort out, for a clear conclusion to be drawn. Some experts suggested that the main change in fertility in the older women was the fact that it took them "longer" to conceive, not necessary that they were significantly more unlikely to eventually succeed. David Dunson, a biostatistician at the U.S. National Institute of Environmental Health Sciences, said that: "Although we noted a decline in female fertility in the late 20s, what we found was a decrease in the probability of becoming pregnant per menstrual cycle, not in the probability of eventually achieving a pregnancy."

A French study found no difference between the fertility rate of women under 25 and those ages 26–30, after which fertility started to decrease. Estimating the "fertility of a woman" is quite difficult because of the male factor (quality of sperm). This French study looked at 2,193 women who were using artificial insemination because their husbands were azoospermic. The cumulative success rates after 12 cycles of insemination were 73% for women under age 25, 74% in women ages 26–30, 61% for ages 31–35, and 54% in the over 35 age group. (Note that the study is from 1982; artificial insemination techniques and success rates have evolved greatly since then.)

In Hungary, a study by the (Central Statistics Office) estimated that 7%–12% of Hungarian women younger than 30 were infertile; 13%–22% of women age 35 were infertile; and 24%–46% of women age 40 were infertile.

The below is a table containing estimates of the percentage of women who, if starting to conceive at a certain age, will fail to obtain a live birth. Note that while for the young ages researchers tend to agree, for older ages there is discrepancy.

Complications of HDN could include kernicterus, hepatosplenomegaly, inspissated (thickened or dried) bile syndrome and/or greenish staining of the teeth, hemolytic anemia and damage to the liver due to excess bilirubin. Similar conditions include acquired hemolytic anemia, congenital toxoplasma and syphilis infection, congenital obstruction of the bile duct and cytomegalovirus infection.

- High at birth or rapidly rising bilirubin

- Prolonged hyperbilirubinemia

- Bilirubin Induced Neuorlogical Dysfunction

- Cerebral Palsy

- Kernicterus

- Neutropenia

- Thrombocytopenia

- Hemolytic Anemia - MUST NOT be treated with iron

- Late onset anemia - Must NOT be treated with iron. Can persist up to 12 weeks after birth.

There is a lack of good evidence to support the use of any particular intervention for morning sickness.

Antenatal depression can be caused by many factors. Often it is associated with the fear and stress of the pregnancy. Other factors include unintended pregnancy, financial issues, living arrangements and relationships with the father & family. Typically, depression symptoms associated with pregnancy are categorized as postnatal depression, due to the onset of symptoms occurring after childbirth has occurred. The following is a breakdown of when a group of various women began to feel the onset of symptoms associated with depression:

- 11.8 percent at 18 weeks

- 13.5 percent at 32 weeks

- 9.1 percent 8 weeks after the birth

- 8.1 percent 8 months after the birth

In a recent article posted by The BabyCenter, the authors stated that "For years, experts mistakenly believed that pregnancy hormones protected against depression, leaving women more vulnerable to the illness only after the baby was born and their hormone levels plunged." This is a possible explanation as to why antenatal depression has just recently been identified.

Co-carcinogens can be a lifestyle like cigarette-smoking, alcohol-drinking or even areca nut tobacco-chewing, which is an Asian tradition, because those activities promote the cytopathic effect (CPE). Also, some virus are co-carcinogens like Herpesviruses, Epstein–Barr virus (EBV) and human herpesvirus 4 (HHV-4) Epstein–Barr virus destroy immune system for human body and then increase the risk of cancer such as Hodgkin’s lymphoma and human immunodeficiency virus because they cause a long term-chronic inflammation for lymphocytes and epithelial cells. Moreover, Over intake beta carotene for a long period of time increased the risk of lung cancer, prostate cancer and many other kind of malignant tumor for cigarette smoker and worker having high contact with asbestos. Generally, co-carcinogen can be irregular eating habits and disease virus and co-carcinogen not only help cancer cell make malignant tumor but also increase the risk of cardiovascular disease and mortality rate.

Antenatal depression affects about one in every eight women. It's becoming more prevalent as more medical studies are being done. Antenatal depression was once thought to simply be the normal stress associated with any pregnancy, and was waved off as a common ailment. It can be caused by many factors, usually though involving aspects of the mothers personal life such as, family, economic standing, relationship status, etc. It can also be caused by hormonal and physical changes that are associated with pregnancy.