Question: What can affect childbirth?

Complications of pregnancy


Complications of pregnancy are health problems that are caused by pregnancy. Complications that occur primarily during childbirth are termed obstetric labor complications, and problems that occur primarily after childbirth are termed puerperal disorders. Severe complications of pregnancy, childbirth, and the puerperium are present in 1.6% of mothers in the US[1] and in 1.5% of mothers in Canada.[2]  In the immediate postpartum period (puerperium), 87% to 94% of women report at least one health problem.[3][4] Long-term health problems (persisting after six months postpartum) are reported by 31% of women.[5]
In 2016, complications of pregnancy, childbirth, and the puerperium resulted globally in 230,600 deaths, down from 377,000 deaths in 1990. The most common causes of maternal mortality are maternal bleeding, maternal sepsis and other infections, hypertensive diseases of pregnancy, obstructed labor, and pregnancy with abortive outcome, which includes miscarriage, ectopic pregnancy, and elective abortion.[6]
There is no clear distinction between complications of pregnancy and symptoms and discomforts of pregnancy. However, the latter do not significantly interfere with activities of daily living or pose any significant threat to the health of the mother or baby. Still, in some cases the same basic feature can manifest as either a discomfort or a complication depending on the severity. For example, mild nausea may merely be a discomfort (morning sickness), but if severe and with vomiting causing water-electrolyte imbalance it can be classified as a pregnancy complication (hyperemesis gravidarum).
Maternal problems
The following problems originate mainly in the mother.
Gestational diabetes
Gestational diabetes is when a woman without diabetes develops high blood sugar levels during pregnancy.[7]
Hyperemesis gravidarum
Hyperemesis gravidarum is the presence of severe and persistent vomiting, causing dehydration and weight loss. It is more severe than the more common morning sickness and is estimated to affect 0.5–2.0% of pregnant women.[8][9]
Pelvic girdle pain
Caused by: Pelvic girdle pain (PGP) disorder is pain caused by instability and limitation of mobility and functioning in any of the three pelvic joints. PGP can begin peri or postpartum. For most women, PGP resolves in the weeks after delivery, but for some it can last for years, resulting in a reduced tolerance for weight bearing activities. PGP affects around 45% of women during pregnancy: 25% report serious pain and 8% are severely disabled.[10]
Treatment: The treatment modality is based on the severity. A mild case would require rest, rehabilitation therapy and pain is usually manageable. More severe cases would also include mobility aids, strong analgesics and sometimes surgery. One of the main factors in helping women cope is with education, information and support. Many treatment options are available.
High blood pressure

Potential severe hypertensive states of pregnancy are mainly:
Preeclampsia – gestational hypertension, proteinuria (>300mg), and edema. Severe preeclampsia involves a BP over 160/110 (with additional signs). It affects 5-8% of pregnancies.[11]
Eclampsia – seizures in a pre-eclamptic patient, affect around 1.4% of pregnancies.[12]
Gestational hypertension
HELLP syndrome – Hemolytic anemia, elevated liver enzymes and a low platelet count. Incidence is reported as 0.5-0.9% of all pregnancies.[13]
Acute fatty liver of pregnancy is sometimes included in the preeclamptic spectrum. It occurs in approximately one in 7,000 to one in 15,000 pregnancies.[14][15]
Deep vein thrombosis
Deep vein thrombosis (DVT) has an incidence of 0.5 to 7 per 1,000 pregnancies, and is the second most common cause of maternal death in developed countries after bleeding.[16]
Caused by: Pregnancy-induced hypercoagulability as a physiological response in preparation for the potential bleeding during childbirth.
Treatment: Prophylactic treatment, e.g. with low molecular weight heparin may be indicated when there are additional risk factors for deep vein thrombosis.[16]
Anemia
Levels of hemoglobin are lower in the third trimesters. According to the United Nations (UN) estimates, approximately half of pregnant women suffer from anemia worldwide. Anemia prevalences during pregnancy differed from 18% in developed countries to 75% in South Asia.[17]
Treatment varies due to the severity of the anaemia, and can be used by increasing iron containing foods, oral iron tablets or by the use of parenteral iron.[18]
Infection


A pregnant woman is more susceptible to certain infections. This increased risk is caused by an increased immune tolerance in pregnancy to prevent an immune reaction against the fetus, as well as secondary to maternal physiological changes including a decrease in respiratory volumes and urinary stasis due to an enlarging uterus.[19] Pregnant women are more severely affected by, for example, influenza, hepatitis E, herpes simplex and malaria.[19] The evidence is more limited for coccidioidomycosis, measles, smallpox, and varicella.[19] Mastitis, or inflammation of the breast occurs in 20% of lactating women.[20]
Some infections are vertically transmissible, meaning that they can affect the child as well.
Peripartum cardiomyopathy
Peripartum cardiomyopathy is decrease in heart function which occurs in the last month of pregnancy, or up to six months post-pregnancy. It increases the risk of congestive heart failure, heart arrhythmias, thromboembolism, and cardiac arrest.[21]
Hypothyroidism

Hypothyroidism (also called Hashimoto's disease) is an autoimmune disease that affects the thyroid in women. This condition can have a profound effect during pregnancy and on the child. The infant may be seriously affected and have a variety of birth defects. Many women with Hashimoto's disease develop an underactive thyroid. The clinician will do an exam and order one or more tests.[22][23][24]
Fetal and placental problems
The following problems occur in the fetus or placenta, but may have serious consequences on the mother as well.
Ectopic pregnancy
Ectopic pregnancy is implantation of the embryo outside the uterus
Caused by: Unknown, but risk factors include smoking, advanced maternal age, and prior surgery or trauma to the fallopian tubes.
Treatment: In most cases, keyhole surgery must be carried out to remove the fetus, along with the fallopian tube. If the pregnancy is very early, it may resolve on its own, or it can be treated with methotrexate, an abortifacient.[25]
Miscarriage
Miscarriage is the loss of a pregnancy prior to 20 weeks.[26] In the UK, miscarriage is defined as the loss of a pregnancy during the first 23 weeks.[27]
Placental abruption
Placental abruption is the separation of the placenta from the uterus.[28]
Caused by: Various causes; risk factors include maternal hypertension, trauma, and drug use.
Treatment: Immediate delivery if the fetus is mature (36 weeks or older), or if a younger fetus or the mother is in distress. In less severe cases with immature fetuses, the situation may be monitored in hospital, with treatment if necessary.
Placenta praevia
Placenta praevia is when the placenta fully or partially covers the cervix.[29]
Placenta accreta
Placenta accreta is an abnormal adherence of the placenta to the uterine wall.[30]
Multiple pregnancies

Multiples may become monochorionic, sharing the same chorion, with resultant risk of twin-to-twin transfusion syndrome. Monochorionic multiples may even become monoamniotic, sharing the same amniotic sac, resulting in risk of umbilical cord compression and entanglement. In very rare cases, there may be conjoined twins, possibly impairing function of internal organs.
Vertically transmitted infection


The embryo and fetus have little or no immune function. They depend on the immune function of their mother. Several pathogens can cross the placenta and cause (perinatal) infection. Often microorganisms that produce minor illness in the mother are very dangerous for the developing embryo or fetus. This can result in spontaneous abortion or major developmental disorders. For many infections, the baby is more at risk at particular stages of pregnancy. Problems related to perinatal infection are not always directly noticeable.
The term TORCH complex refers to a set of several different infections that may be caused by transplacental infection.
Babies can also become infected by their mother during birth. During birth, babies are exposed to maternal blood and body fluids without the placental barrier intervening and to the maternal genital tract. Because of this, blood-borne microorganisms (hepatitis B, HIV), organisms associated with sexually transmitted disease (e.g., gonorrhoea and chlamydia), and normal fauna of the genito-urinary tract (e.g., Candida) are among those commonly seen in infection of newborns.
Intrauterine bleeding
There have been rare but known cases of intrauterine bleeding caused by injury inflicted by the fetus with its fingernails or toenails.[31]
General risk factors
Factors increasing the risk (to either the woman, the fetus/es, or both) of pregnancy complications beyond the normal level of risk may be present in a woman's medical profile either before she becomes pregnant or during the pregnancy.[32] These pre-existing factors may relate to physical or mental health, or to social issues, or a combination of those.[33]
Some common risk factors include:
Age of either parent
Adolescent parents 
Older parents 
Exposure to environmental toxins in pregnancy
Exposure to recreational drugs in pregnancy
Ethanol during pregnancy can cause fetal alcohol syndrome and fetal alcohol spectrum disorder.
Tobacco smoking and pregnancy, when combined, causes twice the risk of premature rupture of membranes, placental abruption and placenta previa.[34] Also, it causes 30% higher odds of the baby being born prematurely.[35]
Prenatal cocaine exposure is associated with, for example, premature birth, birth defects and attention deficit disorder.
Prenatal methamphetamine exposure can cause premature birth and congenital abnormalities.[36] Other investigations have revealed short-term neonatal outcomes to include small deficits in infant neurobehavioral function and growth restriction when compared to control infants.[37] Also, prenatal methamphetamine use is believed to have long-term effects in terms of brain development, which may last for many years.[36]
Cannabis in pregnancy is possibly associated with adverse effects on the child later in life.
Exposure to pharmaceutical drugs in pregnancy:[33] Anti-depressants, for example, may increase risks of such outcomes as preterm delivery.[38] 
Ionizing radiation
Risks arising from previous pregnancies
Complications experienced during a previous pregnancy are more likely to recur.
Many previous pregnancies: Women who have had five previous pregnancies face increased risks of very rapid labor and excessive bleeding after delivery.
Multiple previous fetuses: Women who have had more than one fetus in a previous pregnancy face increased risk of mislocated placenta.[33]
Multiple pregnancy: Having more than one fetus in a single pregnancy.
Social and socioeconomic factors: Generally speaking, unmarried women and those in lower socioeconomic groups experience an increased level of risk in pregnancy, due at least in part to lack of access to appropriate prenatal care.[33]
Unintended pregnancy: Unintended pregnancies preclude preconception care and delays prenatal care.  They preclude other preventive care, may disrupt life plans and on average have worse health and psychological outcomes for the mother and, if birth occurs, the child.[39][40]
Height: Pregnancy in women whose height is less than 1.5 meters (5feet) correlates with higher incidences of preterm birth and underweight babies. Also, these women are more likely to have a small pelvis, which can result in such complications during childbirth as shoulder dystocia.[33]
Weight
Low weight: Women whose pre-pregnancy weight is less than 45.5 kilograms (100 pounds) are more likely to have underweight babies.
Obese women are more likely to have very large babies, potentially increasing difficulties in childbirth. Obesity also increases the chances of developing gestational diabetes, high blood pressure, preeclampsia, experiencing postterm pregnancy and requiring a cesarean delivery.[33]
Intercurrent disease in pregnancy: A disease and condition not necessarily directly caused by the pregnancy, such as diabetes mellitus in pregnancy, SLE in pregnancy or thyroid disease in pregnancy.
High-risk pregnancy
Some disorders and conditions can mean that pregnancy is considered high-risk (about 6-8% of pregnancies in the USA) and in extreme cases may be contraindicated. High-risk pregnancies are the main focus of doctors specialising in maternal-fetal medicine.
Serious pre-existing disorders which can reduce a woman's physical ability to survive pregnancy include a range of congenital defects (that is, conditions with which the woman herself was born, for example, those of the heart or reproductive organs, some of which are listed above) and diseases acquired at any time during the woman's life.
Low-risk pregnancy
A Dutch 2010 research paper showed that "low-risk" pregnancy in the Netherlands may actually carry a higher risk of perinatal death than a "high-risk" pregnancy.[41]
See also
List of complications of pregnancy
List of obstetric topics
Dermatoses of pregnancy
Thyroid in pregnancy
Reproductive Health Supplies Coalition