Developmental toxicity is any structural or functional alteration, reversible or irreversible, which interferes with homeostasis, normal growth, differentiation, development or behavior, and which is caused by environmental insult (including drugs, lifestyle factors such as alcohol, diet, and environmental toxic chemicals or physical factors). It is the study of adverse effects on the development of the organism resulting from exposure to toxic agents before conception (either parent), during prenatal development, or post-natally until puberty. The substance that causes developmental toxicity from embryonic stage to birth is called teratogens. The effect of the developmental toxicants depends on the type of substance, dose and duration and time of exposure.

Certain Pathogens are also included since the toxins they secrete are known to cause adverse effects on the development of the organism when the mother or fetus is infected. Developmental toxicology is a science studying adverse developmental outcomes. This term has widely replaced the early term for the study of primarily structural congenital abnormalities, teratology, to enable inclusion of a more diverse spectrum of congenital disorders. Typical factors causing developmental toxicity are radiation, infections (e.g. rubella), maternal metabolic imbalances (e.g. alcoholism, diabetes, folic acid deficiency), drugs (e.g. anticancer drugs, tetracyclines, many hormones, thalidomide), and environmental chemicals (e.g. mercury, lead, dioxins, PBDEs, HBCD, tobacco smoke). The first-trimester exposure is considered the most potential for developmental toxicity.

Once fertilization has taken place, the toxicants in the environment can pass through the mother to the developing embryo or fetus across the placental barrier. The fetus is at greatest risk during the first 14th to 60th day of the pregnancy when the major organs are being formed. However, depending on the type of toxicant and amount of exposure, a fetus can be exposed toxicant at any time during pregnancy. For example, exposure to a particular toxicant at one time in the pregnancy may result in organ damage and at another time in the pregnancy could cause death of the fetus and miscarriage. There are a number of chemicals, biological agents (such as bacteria and viruses), and physical agents (such as radiation) used in a variety of workplaces that are known to cause developmental disorders. Developmental disorders can include a wide range of physical abnormalities, such as bone or organ deformities, or behavioral and learning problems, such as a mental retardation. Exposures to some chemicals during pregnancy can lead to the development of cancer later in the life of the child and are called transgenerational carcinogens. Exposure to toxicants during the second and the third trimester of a pregnancy can lead to slow fetal grown and result in low birth weight.

Twin-to-twin transfusion syndrome (TTTS), also known as feto-fetal transfusion syndrome (FFTS) and twin oligohydramnios-polyhydramnios sequence (TOPS) is a complication of disproportionate blood supply, resulting in high morbidity and mortality. It can affect monochorionic multiples, that is, multiple pregnancies where two or more fetuses share a chorion and hence a single placenta. Severe TTTS has a 60–100% mortality rate.

Drug use during pregnancy can have temporary or permanent effects on the fetus. Any drug that acts during embryonic or fetal development to produce a permanent alteration of form or function is known as a teratogen. Drugs may refer to both pharmaceutical drug and recreational drugs.

Swelling (especially in the hands and face) was originally considered an important sign for a diagnosis of pre-eclampsia. However, because swelling is a common occurrence in pregnancy, its utility as a distinguishing factor in pre-eclampsia is not high. Pitting edema (unusual swelling, particularly of the hands, feet, or face, notable by leaving an indentation when pressed on) can be significant, and should be reported to a health care provider.

In general, none of the signs of pre-eclampsia are specific, and even convulsions in pregnancy are more likely to have causes other than eclampsia in modern practice. Further, a symptom such as epigastric pain may be misinterpreted as heartburn. Diagnosis, therefore, depends on finding a coincidence of several pre-eclamptic features, the final proof being their regression after delivery.

The symptoms and discomforts of pregnancy are those presentations and conditions that result from pregnancy but do not significantly interfere with activities of daily living or pose a threat to the health of the mother or baby. This is in contrast to pregnancy complications. Sometimes a symptom that is considered a discomfort can be considered a complication when it is more severe. For example, nausea (morning sickness) can be a discomfort, but if, in combination with significant vomiting it causes a water-electrolyte imbalance, it is a complication known as hyperemesis gravidarum.

Common symptoms and discomforts of pregnancy include:

- Tiredness.

- Constipation

- Pelvic girdle pain

- Back pain

- Braxton Hicks contractions. Occasional, irregular, and often painless contractions that occur several times per day.

- Edema (swelling). Common complaint in advancing pregnancy. Caused by compression of the inferior vena cava and pelvic veins by the uterus leads to increased hydrostatic pressure in lower extremities.

- Increased urinary frequency. A common complaint, caused by increased intravascular volume, elevated glomerular filtration rate, and compression of the bladder by the expanding uterus.

- Urinary tract infection

- Varicose veins. Common complaint caused by relaxation of the venous smooth muscle and increased intravascular pressure.

- Haemorrhoids (piles). Swollen veins at or inside the anal area. Caused by impaired venous return, straining associated with constipation, or increased intra-abdominal pressure in later pregnancy.

- Regurgitation, heartburn, and nausea.

- Stretch marks

- Breast tenderness is common during the first trimester, and is more common in women who are pregnant at a young age.

In addition, pregnancy may result in pregnancy complication such as deep vein thrombosis or worsening of an intercurrent disease in pregnancy.

Each year, ill health as a result of pregnancy is experienced (sometimes permanently) by more than 20 million women around the world. In 2013 complications of pregnancy resulted in 293,000 deaths down from 377,000 deaths in 1990. Common causes include maternal bleeding (44,000), complications of abortion (44,000), high blood pressure of pregnancy (29,000), maternal sepsis (24,000), and obstructed labor (19,000).

The following are some examples of pregnancy complications:

- Pregnancy induced hypertension

- Anemia

- Postpartum depression

- Postpartum psychosis

- Thromboembolic disorders. These are the leading cause of death in pregnant women in the US.

- PUPPP (Pruritic Urticarial Papules and Plaques of Pregnancy), a skin disease that develops around the 32nd week. Signs are red plaques, papules, and itchiness around the belly button that then spreads all over the body except for the inside of hands and face.

- Ectopic pregnancy, implantation of the embryo outside the uterus.

- Hyperemesis gravidarum, excessive nausea and vomiting that is more severe than normal morning sickness.

- Pulmonary embolism, blood clots that form in the legs that can migrate to the lungs.

There is also an increased susceptibility and severity of certain infections in pregnancy.

Congenital rubella syndrome (CRS) can occur in a developing fetus of a pregnant woman who has contracted rubella, usually in the first trimester. If infection occurs 0–28 days before conception, the infant has a 43% risk of being affected. If the infection occurs 0–12 weeks after conception, the risk increases to 51%. If the infection occurs 13–26 weeks after conception, the risk is 23% of the infant being affected by the disease. Infants are not generally affected if rubella is contracted during the third trimester, or 26–40 weeks after conception. Problems rarely occur when rubella is contracted by the mother after 20 weeks of gestation and continues to disseminate the virus after birth.

It was discovered in 1941 by Australian Norman McAlister Gregg.

A staging system proposed by fetal surgeon Dr. Ruben Quintero is commonly used to classify the severity of TTTS.

Stage I: A small amount of amniotic fluid (oligohydramnios) is found around the donor twin and a large amount of amniotic fluid (polyhydramnios) is found around the recipient twin.

Stage II: In addition to the description above, the ultrasound is not able to identify the bladder in the donor twin.

Stage III: In addition to the characteristics of Stages I and II, there is abnormal blood flow in the umbilical cords of the twins.

Stage IV: In addition to all of the above findings, the recipient twin has swelling under the skin and appears to be experiencing heart failure (fetal hydrops).

Stage V: In addition to all of the above findings, one of the twins has died. This can happen to either twin. The risk to either the donor or the recipient is roughly equal & is quite high in Stage II or higher TTTS.

The Quintero staging does not provide information about prognosis, and other staging systems have been proposed.

The classic triad for congenital rubella syndrome is:

- Sensorineural deafness (58% of patients)

- Eye abnormalities—especially retinopathy, cataract, and microphthalmia (43% of patients)

- Congenital heart disease—especially pulmonary artery stenosis and patent ductus arteriosus (50% of patients)

Other manifestations of CRS may include:

- Spleen, liver, or bone marrow problems (some of which may disappear shortly after birth)

- Intellectual disability

- Small head size (microcephaly)

- Eye defects

- Low birth weight

- Thrombocytopenic purpura

- Extramedullary hematopoiesis (presents as a characteristic blueberry muffin rash)

- Hepatomegaly

- Micrognathia

Children who have been exposed to rubella in the womb should also be watched closely as they age for any indication of:

- Developmental delay

- Autism

- Schizophrenia

- Growth retardation

- Learning disabilities

- Diabetes mellitus

- Glaucoma

Pre-eclampsia (PE) is a disorder of pregnancy characterized by the onset of high blood pressure and often a significant amount of protein in the urine. The condition begins after 20 weeks of pregnancy. In severe disease there may be red blood cell breakdown, a low blood platelet count, impaired liver function, kidney dysfunction, swelling, shortness of breath due to fluid in the lungs, or visual disturbances. Pre-eclampsia increases the risk of poor outcomes for both the mother and the baby. If left untreated, it may result in seizures at which point it is known as eclampsia.

Risk factors for pre-eclampsia include obesity, prior hypertension, older age, and diabetes mellitus. It is also more frequent in a woman's first pregnancy and if she is carrying twins. The underlying mechanism involves abnormal formation of blood vessels in the placenta amongst other factors. Most cases are diagnosed before delivery. Rarely, pre-eclampsia may begin in the period after delivery. While historically both high blood pressure and protein in the urine were required to make the diagnosis, some definitions also include those with hypertension and any associated organ dysfunction. Blood pressure is defined as high when it is greater than 140 mmHg systolic or 90 mmHg diastolic at two separate times, more than four hours apart in a woman after twenty weeks of pregnancy. Pre-eclampsia is routinely screened for during prenatal care.

Recommendations for prevention include: aspirin in those at high risk, calcium supplementation in areas with low intake, and treatment of prior hypertension with medications. In those with pre-eclampsia delivery of the baby and placenta is an effective treatment. When delivery becomes recommended depends on how severe the pre-eclampsia and how far along in pregnancy a person is. Blood pressure medication, such as labetalol and methyldopa, may be used to improve the mother's condition before delivery. Magnesium sulfate may be used to prevent eclampsia in those with severe disease. Bedrest and salt intake have not been found to be useful for either treatment or prevention.

Pre-eclampsia affects 2–8% of pregnancies worldwide. Hypertensive disorders of pregnancy (which include pre-eclampsia) are one of the most common causes of death due to pregnancy. They resulted in 46,900 deaths in 2015. Pre-eclampsia usually occurs after 32 weeks; however, if it occurs earlier it is associated with worse outcomes. Women who have had pre-eclampsia are at increased risk of heart disease and stroke later in life. The word eclampsia is from the Greek term for lightning. The first known description of the condition was by Hippocrates in the 5th century BC.

Developmental toxicity is the alterations of the developmental processes (organogenesis, morphogenesis) rather than functional alterations of already developed organs. The effects of the toxicants depends on the dose, threshold and duration. The effects of toxicity are:

1. Minor structural deformities - e.g. Anticonvulsant drugs, Warfarin, Retinoic Acid derivatives

2. Major structural deformities - e.g. DES (diethylstilbestrol), cigarette smoking

3. Growth Retardation - e.g. Alcohol, Polychlorinated Biphenyls

4. Functional alterations - e.g. Retinoic Acid derivatives, Polychlorinated Biphenyls, Phenobarbitol, Lead

5. Death- e.g. Rubella, ACE inhibitors

Up to 10% of women with ectopic pregnancy have no symptoms, and one-third have no medical signs. In many cases the symptoms have low specificity, and can be similar to those of other genitourinary and gastrointestinal disorders, such as appendicitis, salpingitis, rupture of a corpus luteum cyst, miscarriage, ovarian torsion or urinary tract infection. Clinical presentation of ectopic pregnancy occurs at a mean of 7.2 weeks after the last normal menstrual period, with a range of 4 to 8 weeks. Later presentations are more common in communities deprived of modern diagnostic ability.

Signs and symptoms of ectopic pregnancy include increased hCG, vaginal bleeding (in varying amounts), sudden lower abdominal pain, pelvic pain, a tender cervix, an adnexal mass, or adnexal tenderness. In the absence of ultrasound or hCG assessment, heavy vaginal bleeding may lead to a misdiagnosis of miscarriage. Nausea, vomiting and diarrhea are more rare symptoms of ectopic pregnancy.

Rupture of an ectopic pregnancy can lead to symptoms such as abdominal distension, tenderness, peritonism and hypovolemic shock. A woman with ectopic pregnancy may be excessively mobile with upright posturing, in order to decrease intrapelvic blood flow, which can lead to swelling of the abdominal cavity and cause additional pain.

When structural impairments are not observable or do not exist, neurological impairments are assessed. In the context of FASD, neurological impairments are caused by prenatal alcohol exposure which causes general neurological damage to the central nervous system (CNS), the peripheral nervous system, or the autonomic nervous system. A determination of a neurological problem must be made by a trained physician, and must not be due to a postnatal insult, such as a high fever, concussion, traumatic brain injury, etc.

All four diagnostic systems show virtual agreement on their criteria for CNS damage at the neurological level, and evidence of a CNS neurological impairment due to prenatal alcohol exposure will result in a diagnosis of FAS or pFAS, and functional impairments are highly likely.

Neurological problems are expressed as either hard signs, or diagnosable disorders, such as epilepsy or other seizure disorders, or soft signs. Soft signs are broader, nonspecific neurological impairments, or symptoms, such as impaired fine motor skills, neurosensory hearing loss, poor gait, clumsiness, poor eye-hand coordination. Many soft signs have norm-referenced criteria, while others are determined through clinical judgment. "Clinical judgment" is only as good as the clinician, and soft signs should be assessed by either a pediatric neurologist, a pediatric neuropsychologist, or both.

Other conditions may commonly co-occur with FAS, stemming from prenatal alcohol exposure. However, these conditions are considered alcohol-related birth defects and not diagnostic criteria for FAS.

- Heart: A heart murmur that frequently disappears by one year of age. Ventricular septal defect most commonly seen, followed by an atrial septal defect.

- Bones: Joint anomalies including abnormal position and function, altered palmar crease patterns, small distal phalanges, and small fifth fingernails.

- Kidneys: Horseshoe, aplastic, dysplastic, or hypoplastic kidneys.

- Eyes: Strabismus, optic nerve hypoplasia (which may cause light sensitivity, decreased visual acuity, or involuntary eye movements).

- Occasional problems: ptosis of the eyelid, microophthalmia, cleft lip with or without a cleft palate, webbed neck, short neck, tetralogy of Fallot, coarctation of the aorta, spina bifida, and hydrocephalus.

Ectopic pregnancy, also known as tubal pregnancy, is a complication of pregnancy in which the embryo attaches outside the uterus. Signs and symptoms classically include abdominal pain and vaginal bleeding. Less than 50 percent of affected women have both of these symptoms. The pain may be described as sharp, dull, or crampy. Pain may also spread to the shoulder if bleeding into the abdomen has occurred. Severe bleeding may result in a fast heart rate, fainting, or shock. With very rare exceptions the fetus is unable to survive.

Risk factors for ectopic pregnancy include: pelvic inflammatory disease, often due to Chlamydia infection, tobacco smoking, prior tubal surgery, a history of infertility, and the use of assisted reproductive technology. Those who have previously had an ectopic pregnancy are at much higher risk of having another one. Most ectopic pregnancies (90%) occur in the Fallopian tube which are known as tubal pregnancies. Implantation can also occur on the cervix, ovaries, or within the abdomen. Detection of ectopic pregnancy is typically by blood tests for human chorionic gonadotropin (hCG) and ultrasound. This may require testing on more than one occasion. Ultrasound works best when performed from within the vagina. Other causes of similar symptoms include: miscarriage, ovarian torsion, and acute appendicitis.

Prevention is by decreasing risk factors such as chlamydia infections through screening and treatment. While some ectopic pregnancies will resolve without treatment, this approach has not been well studied as of 2014. The use of the medication methotrexate works as well as surgery in some cases. Specifically it works well when the beta-HCG is low and the size of the ectopic is small. Surgery is still typically recommended if the tube has ruptured, there is a fetal heartbeat, or the person's vital signs are unstable. The surgery may be laparoscopic or through a larger incision, known as a laparotomy. Outcomes are generally good with treatment.

The rate of ectopic pregnancy is about 1 and 2% that of live births in developed countries, though it may be as high as 4% among those using assisted reproductive technology. It is the most common cause of death among women during the first trimester at approximately 10% of the total. In the developed world outcomes have improved while in the developing world they often remain poor. The risk of death among those in the developed world is between 0.1 and 0.3 percent while in the developing world it is between one and three percent. The first known description of an ectopic pregnancy is by Al-Zahrawi in the 11th century. The word "ectopic" means "out of place".

Vitamin D deficiency has become a worldwide health epidemic with clinical rates on the rise. In the years of 2011-12, it was estimated that around 4 million adults were considered deficient in Vitamin D throughout Australia. The Australian Bureau of Statistics (ABS) found 23%, or one in four Australian adults suffer from some form of Vitamin D deficiency. Outlined throughout the article are the causes of increase through subgroups populations, influencing factors and strategies in place to control deficiency rates throughout Australia.

The apprehension is not necessarily data driven and is a cautionary response to the lack of clinical studies in pregnant women. The indication is a trade-off between the adverse effects of the drug, the risks associated with intercurrent diseases and pregnancy complications, and the efficiency of the drug to prevent or ameliorate such risks. In some cases, the use of drugs in pregnancy carries benefits that outweigh the risks. For example, high fever is harmful for the fetus in the early months, thus the use of paracetamol (acetaminophen) is generally associated with lower risk than the fever itself. Similarly, diabetes mellitus during pregnancy may need intensive therapy with insulin to prevent complications to mother and baby. Pain management for the mother is another important area where an evaluation of the benefits and risks is needed. NSAIDs such as Ibuprofen and Naproxen are probably safe for use for a short period of time, 48–72 hours, once the mother has reached the second trimester. If taking aspirin for pain management the mother should never take a dose higher than 100 mg.

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.

About 66% of women have both nausea and vomiting while 33% have just nausea.

A vitamin deficiency can cause a disease or syndrome known as an avitaminosis or hypovitaminosis. This usually refers to a long-term deficiency of a vitamin. When caused by inadequate nutrition it can be classed as a "primary deficiency", and when due to an underlying disorder such as malabsorption it can be classed as a "secondary deficiency". An underlying disorder may be metabolic as in a defect converting tryptophan to niacin. It can also be the result of lifestyle choices including smoking and alcohol consumption.

Examples are vitamin A deficiency, folate deficiency, scurvy, vitamin D deficiency, vitamin E deficiency, and vitamin K deficiency. In the medical literature, any of these may also be called by names on the pattern of "hypovitaminosis" or "avitaminosis" + "[letter of vitamin]", for example, hypovitaminosis A, hypovitaminosis C, hypovitaminosis D.

Conversely hypervitaminosis is the syndrome of symptoms caused by over-retention of fat-soluble vitamins in the body.

- Vitamin A deficiency can cause keratomalacia.

- Thiamine (vitamin B1) deficiency causes beriberi and Wernicke–Korsakoff syndrome.

- Riboflavin (vitamin B2) deficiency causes ariboflavinosis.

- Niacin (vitamin B3) deficiency causes pellagra.

- Pantothenic acid (vitamin B5) deficiency causes chronic paresthesia.

- Vitamin B6

- Biotin (vitamin B7) deficiency negatively affects fertility and hair/skin growth. Deficiency can be caused by poor diet or genetic factors (such as mutations in the BTD gene, see multiple carboxylase deficiency).

- Folate (vitamin B9) deficiency is associated with numerous health problems. Fortification of certain foods with folate has drastically reduced the incidence of neural tube defects in countries where such fortification takes place. Deficiency can result from poor diet or genetic factors (such as mutations in the MTHFR gene that lead to compromised folate metabolism).

- Vitamin B12 (cobalamin) deficiency can lead to pernicious anemia, megaloblastic anemia, subacute combined degeneration of spinal cord, and methylmalonic acidemia among other conditions.

- Vitamin C (ascorbic acid) short-term deficiency can lead to weakness, weight loss and general aches and pains. Longer-term depletion may affect the connective tissue. Persistent vitamin C deficiency leads to scurvy.

- Vitamin D (cholecalciferol) deficiency is a known cause of rickets, and has been linked to numerous health problems.

- Vitamin E deficiency causes nerve problems due to poor conduction of electrical impulses along nerves due to changes in nerve membrane structure and function.

- Vitamin K (phylloquinone or menaquinone) deficiency causes impaired coagulation and has also been implicated in osteoporosis

Cannabis consumption in pregnancy might be associated with restrictions in growth of the fetus, miscarriage, and cognitive deficits. The American Congress of Obstetricians and Gynecologists recommended that cannabis use be stopped before and during pregnancy, Cannabis is the most commonly used illicit substance

among pregnant women.

Although it is difficult to draw firm conclusions, there is some evidence that prenatal exposure to marijuana may be associated with deficits in language, attention, cognitive performance, and delinquent behaviors. THC exposure in rats during the prenatal developmental phase may cause epigenetic changes in gene expression, but there is limited knowledge about the risk for psychiatric disorders because of ethical barriers to studying the developing human brain. While animal studies cannot take into account factors that could influence the effects of cannabis on human maternal exposure, such as environmental and social factors, a 2011 review of rodent studies by Campolongo "et al." said there was "... increasing evidence from animal studies showing that cannabinoid drugs ... induce enduring neurobehavioral abnormalities in the exposed offspring ..." Campolongo "et al." added that "clinical studies report hyperactivity, cognitive impairments and altered emotionality in humans exposed in utero to cannabis". Martin "et al." investigated recent trends in substance abuse treatment admissions for cannabis use in pregnancy in the US, based on Treatment Episodes Data Set (TEDS) from 1992 to 2012, and discovered that, while the proportion of treatment admissions for pregnant women was stable (about 4%), the admissions for women who were pregnant and reported any marijuana use grew from 29% to 43%. A 2015 review found that cannabis use by pregnant mothers impaired brain maturation in their children, and that it also predisposed their children to neurodevelopmental disorders.

The cause of morning sickness is unknown. While some have claimed it to be due to psychological reasons, this is not supported by evidence.

Nausea and vomiting may also occur with molar pregnancy.

This defect leads to a multi-systemic disorder of the connective tissue, muscles, central nervous system (CNS), and cardiovascular system. Homocystinuria represents a group of hereditary metabolic disorders characterized by an accumulation of the amino acid homocysteine in the serum and an increased excretion of homocysteine in the urine. Infants appear to be normal and early symptoms, if any are present, are vague.

Signs and symptoms of homocystinuria that may be seen include the following:

Vitamin D plays an important role in which it supports calcium absorption in the body, sustaining good bone health as well as muscle function. When calcium in the body becomes underprovided for normal bodily functions, calcitriol, an active form of Vitamin D, pairs with parathyroid hormone. Together they act to assemble cells in order to increase the calcium stores taken from bone.

The popular term Sunshine vitamin, as it’s often called, is one of the one main sources of achieving sufficient Vitamin D through sunlight on the skin known as D3. The second form is commonly known as D2, which is found in foods such as fatty fish and fortified products like margarine and milk.

Additionally, if you consume vitamin D through your diet, or make vitamin D in your skin from UVB exposure, it is processed through two organs before it becomes activated. Vitamin D is first processed in the liver, before heading to the kidneys where it becomes activated to the form 1-25 dihydroxy vitamin D or alternatively named chemical calcitriol.

Classical homocystinuria, also known as cystathionine beta synthase deficiency or CBS deficiency, is an inherited disorder of the metabolism of the amino acid methionine, often involving cystathionine beta synthase. It is an inherited autosomal recessive trait, which means a child needs to inherit a copy of the defective gene from both parents to be affected.