Overview of pregnancy complications

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Last reviewed: 3 Nov 2024

Last updated: 30 Jan 2024

This page compiles our content related to pregnancy complications. For further information on diagnosis and treatment, follow the links below to our full BMJ Best Practice topics on the relevant conditions and symptoms.

Complications in pregnancy can result from conditions that are specifically linked to the pregnant state as well as conditions that commonly arise or occur incidentally in women who are pregnant. Serious sequelae might include miscarriage, pre-term labour or premature rupture of membranes, premature birth, stillbirth, low birth weight, macrosomia, birth defects, and infant and maternal morbidity or death. Complications affecting mother and fetus may arise at any stage of pregnancy, during labour, or postpartum.

Condition	Description
Routine antenatal care	go to our full topic on Routine antenatal care Antenatal care is a key component of a healthy pregnancy. Regular antenatal care helps to identify and treat complications and to promote healthy behaviours.
Nausea and vomiting in pregnancy	go to our full topic on Nausea and vomiting in pregnancy Nausea and vomiting in pregnancy (NVP), commonly referred to as morning sickness, typically begins between the fourth and eighth week after the last menstrual period. It is characterised by nausea and vomiting that occurs more frequently during the morning hours, and typically resolves in the second trimester. NVP occurs in up to 50% to 80% of pregnant women.[1] Hyperemesis gravidarum is the most severe form of NVP and is characterised by persistent vomiting, volume depletion, ketosis, electrolyte disturbances, and weight loss.
Folate deficiency	go to our full topic on Folate deficiency Pregnant and lactating women have an increased folate demand, which can result in folate deficiency. Folate deficiency during pregnancy is strongly associated with fetal neural tube defects, 70% of which can be prevented by increased folic acid supplementation.[2][3][4] Symptomatic enquiry should cover symptoms associated with anaemia, including fatigue, palpitations, shortness of breath, dizziness, headaches, jaundice, loss of appetite, and weight loss.
Iron deficiency anaemia	go to our full topic on Iron deficiency anaemia In pregnant women, iron deficiency anaemia is defined as haemoglobin <11 g/dL (110 g/L).[5] Symptoms include fatigue, low energy levels, and dyspnoea on exertion. Pregnancy increases demand for iron with a net loss of approximately 580 mg of iron during the gestation period, with the highest loss occurring in the third trimester.[6][7] Iron deficiency during the first 2 trimesters is associated with an increase in pre-term delivery and low birth-weight babies.[8]
Miscarriage	go to our full topic on Miscarriage Defined as an involuntary, spontaneous loss of a pregnancy before 20-24 completed weeks (gestation varies, depending on country).[9] It is associated with unprovoked vaginal bleeding with or without supra-pubic pain. Miscarriage occurs in up to one third of pregnancies.[10][11][12][13][14] Key risk factors include older parental age, uterine malformation, bacterial vaginosis, and thrombophilias. Serial serum beta hCG titres and a transvaginal ultrasound scan aid in diagnosis.
Assessment of recurrent miscarriage	go to our full topic on Assessment of recurrent miscarriage More than one-half of women with recurrent miscarriage have unexplained or idiopathic recurrent miscarriage, where no cause or association can be identified.[15][16] Increasing maternal age and number of previous miscarriages increase the risk of further miscarriages. Definitive associations of recurrent miscarriage include chromosomal abnormalities, antiphospholipid syndrome, certain structural uterine abnormalities such as cervical incompetence, and certain thrombophilias.
Ectopic pregnancy	go to our full topic on Ectopic pregnancy A fertilised ovum implanting and maturing outside of the uterine endometrial cavity, with the most common site being the fallopian tube (97%), followed by the ovary (3.2%) and the abdomen (1.3%).[17] Classic symptoms and signs are pain, vaginal bleeding, and amenorrhoea.[18] Global rates of ectopic pregnancy are 1.1% in the UK, 1.23% in the US, 1.49% in Norway, and 1.62% in Australia.[19][20][21][22] Red flags suggesting possible rupture include unstable vital signs (orthostatic changes), blood in the vaginal vault, or signs of intraperitoneal bleeding (e.g., acute abdomen, shoulder pain, cervical motion tenderness). Risk increases with prior ectopic pregnancy, tubal surgery, history of sexually transmitted infections, smoking, in vitro fertilisation, or if pregnant despite intrauterine device usage.
Placenta praevia	go to our full topic on Placenta praevia Classified as placenta praevia if the placenta is directly covering the cervical os, or as low-lying placenta if the placental edge is <2 cm from the cervical os. Occurs in 0.3% to 0.5% of pregnancies worldwide.[23][24][25] Symptomatic placenta praevia typically presents as second or third trimester painless vaginal bleeding.[26][27][28] Risk factors include previous uterine scarring (most commonly due to prior caesarean section), advanced maternal age, smoking, previous multiple pregnancies/short inter-pregnancy intervals or miscarriages/induced abortions, prior placenta praevia, infertility treatment, and illicit drug use.
Molar pregnancies	go to our full topic on Molar pregnancies Hydatidiform moles are chromosomally abnormal pregnancies that have the potential to become malignant (gestational trophoblastic neoplasia). Gestational trophoblastic disease (GTD) includes tumours of fetal tissues, including hydatidiform moles, arising from placental trophoblasts. The most common presenting symptom is vaginal bleeding and patients typically present in the first trimester. Women with molar pregnancies are commonly at the extremes of reproductive life (younger than 20 years of age or over 35 years of age), and may relate a history of prior GTD.[29][30]
Assessment of abdominal pain in pregnancy	go to our full topic on Assessment of abdominal pain in pregnancy Early pregnancy causes of abdominal pain include ectopic pregnancy, miscarriage and ovarian hyper-stimulation syndrome. Late pregnancy causes include pre-term labour, chorioamnionitis, uterine rupture, placental abruption, HELLP syndrome, and acute fatty liver of pregnancy. Gynaecological causes include adnexal masses and fibroids. Other aetiologies can be urological (e.g., urinary tract infections [UTIs], acute pyelonephritis, nephrolithiasis, and hydro-nephrosis), gastrointestinal (e.g., appendicitis, cholecystitis, pancreatitis, and intestinal obstruction), trauma-related, and musculoskeletal.
Gestational hypertension	go to our full topic on Gestational hypertension Defined by a blood pressure of ≥140/90 mmHg on two occasions (at least 4 hours apart) during pregnancy after 20 weeks gestation in a previously normotensive woman, without the presence of proteinuria (<300 mg/24 hours) or other clinical features suggestive of pre-eclampsia (thrombocytopenia, impaired renal or kidney function, pulmonary oedema, or new-onset headache).[31][32] Hypertension is the most frequently identified medical problem during pregnancy. Women with gestational hypertension are usually asymptomatic. Risk factors include nulligravidity, black or Hispanic ethnicity, multiple pregnancies, obesity, and mothers who were born small for their gestational age. Gestational hypertension increases the risk of macrosomia, intrauterine growth restriction, stillbirth, caesarean delivery, and admission of the neonate to the intensive care unit. Co-existence of gestational diabetes mellitus further increases the risk.[33]
Gestational diabetes mellitus	go to our full topic on Gestational diabetes mellitus Hyperglycaemia in pregnancy that is below the diagnostic thresholds for diabetes mellitus.[34][35] Develops during pregnancy and is usually diagnosed following assessment for risk factors followed by elevated plasma glucose levels on glucose tolerance testing. It is estimated that in 2021, 16.7% of pregnancies worldwide that resulted in live births were affected by some form of hyperglycaemia.[36] Risk factors include advanced maternal age (>40 years), previous gestational diabetes mellitus, previous macrosomic baby, elevated BMI, polycystic ovarian syndrome, non-white ancestry, family history of type 2 diabetes mellitus, lack of exercise, and prior gestational diabetes mellitus.[37][38][39][40][41][42][43][44][45] Pregnancy can also be complicated by established type 1 or type 2 diabetes mellitus.
Urinary tract infections in women	go to our full topic on Urinary tract infections in women An infection of the kidneys, bladder, or urethra. UTIs in pregnancy are considered to be complicated UTIs. Lifetime incidence of UTIs is 50% to 60% in adult women. Pregnant women should be screened for asymptomatic bacteriuria as it has been associated with higher rates of pyelonephritis, premature labour, and fetal mortality.[1]
Vaginitis	go to our full topic on Vaginitis Inflammation of the vagina due to changes in the composition of the vaginal micro-environment from infection, irritants, or from hormonal deficiency (e.g., atrophic vaginitis). Bacterial vaginosis continues to be a leading cause of vaginitis; other common infectious causes include trichomoniasis and candidiasis. Vaginitis is the most common gynaecological diagnosis in the primary care setting.[46] Common symptoms include discharge, pruritus, and dyspareunia. Bacterial vaginosis and trichomoniasis have been associated with pre-term delivery, low birth weight, and premature rupture of membranes.[47][48]
Listeriosis	go to our full topic on Listeriosis A food-borne infection caused by a motile, non-spore-forming, gram-positive bacillus. Pregnant women are advised to avoid raw unwashed vegetables, raw or undercooked meat (poultry, beef, pork), leftover food, soft cheeses, and unpasteurised milk or its products.[49][50][51][52] The pathogen has a predilection for neonates (aged <1 month), adults (especially >50 years), pregnant women (30% of all patients), and immunocompromised people (with HIV/AIDS, cancer, haematological malignancies, those undergoing corticosteroid treatment, or transplant recipients).[49][53][54] Pregnant women may have flu-like symptoms (lethargy, fever, arthralgias, myalgias, rigors, fatigue, diarrhoea, vomiting, and abdominal pain).[50]
Toxoplasmosis	go to our full topic on Toxoplasmosis Parasitic disease caused by the protozoan Toxoplasma gondii. Spreads through food or water contaminated with oocysts, infected meat, or contact with oocysts from feline faeces. Transplacental transmission results only when a seronegative woman acquires toxoplasmosis during pregnancy. Primary infection during pregnancy is often asymptomatic in the mother, but can result in fetal death and severe congenital abnormalities (e.g., intellectual disability and blindness). National surveys in France have shown a decreasing T gondii seroprevalence among pregnant women, with models estimating a decrease in prevalence from 76% in 1980 to 27% in 2020.[55] Fetal infections in the third trimester are often asymptomatic at birth, but the majority of these congenitally infected children (up to 85%) develop retinitis, central nervous system problems (e.g., learning disabilities or seizures) or delayed growth months to years later.[56] Routine antenatal screening for T gondii is recommended in some countries (e.g., France).
Cytomegalovirus infection	go to our full topic on Cytomegalovirus infection Cytomegalovirus (CMV) is a ubiquitous beta-herpes virus that infects the majority of humans and establishes a state of lifelong latency in host cells. Periodic sub-clinical re-activations are controlled by a functioning immune system. The immunologically-naive fetus is at risk of congenital CMV disease and its complications, such as hearing loss and neurological deficits. It is the most common congenital infectious cause of sensorineural hearing loss and intellectual disability.[57] Pregnant mothers should wash their hands regularly and thoroughly to prevent primary infection (which is usually asymptomatic).
Rubella	go to our full topic on Rubella Maternal infection in pregnancy, particularly early in gestation, may cause spontaneous abortion, fetal death, or a wide spectrum of anatomical and laboratory anomalies (congenital rubella syndrome). In the World Health Organization European Region, rubella incidence declined from 234.9 cases per million population in 2005 to 0.7 cases per million by 2019.[58] Specialty consultation is strongly recommended for pregnant women with exposure to rubella.
Zika virus	go to our full topic on Zika virus A mild, usually self-limited infection when symptomatic (about 20% of infections) caused by the Zika virus. Characteristic clinical findings include fever, an itchy maculopapular (sometimes morbilliform) rash, arthralgia, and non-purulent conjunctivitis.[59] No differences in clinical presentation have been described between pregnant women and non-pregnant patients. Data from the US Zika Pregnancy and Infant Registry found that among pregnancies with confirmed infection, the frequency of any Zika-associated birth defect was higher among those with first (8%) and second (6%) trimester infections compared with third trimester infections (3.8%).[60] Congenital Zika syndrome is a pattern of congenital anomalies (i.e., microcephaly, intracranial calcifications or other brain anomalies, or eye anomalies, among others) in infants associated with Zika virus infection during pregnancy.[61][62][63][64]
HIV infection in pregnancy	go to our full topic on HIV infection in pregnancy It is recommended that all pregnant women be tested for HIV infection as early as possible in pregnancy.[65] All pregnant women with HIV should receive antiretroviral therapy (ART), as early as possible in the pregnancy, regardless of CD4 count or viral load. Approximately 1.3 million (range 1 to 1.6 million) women with HIV worldwide were pregnant in 2021, of whom an estimated 81% received ART.[66] Untreated, the risk of perinatal transmission of HIV is between 15% and 45%, but can be lowered to 1% or less with a combination of preventative measures including ART for mothers and prophylaxis for neonates.[67]
Group B streptococcal infection	go to our full topic on Group B streptococcal infection Group B streptococci (GBS), also known as Streptococcus agalactiae, are gram-positive bacteria that normally colonise the gastrointestinal tract, perineum, and vagina.[68] They can cause invasive infections at any age but infections are most common in the neonatal period, in older people, and in adults with predisposing factors (i.e., pregnancy, diabetes mellitus, immunocompromised).[68] Approximately 10% to 30% of pregnant women are colonised with GBS in the rectum or vagina; in the absence of intervention, around 1% to 2% of babies born to colonised mothers will develop early-onset GBS infection.[69] GBS can produce a wide range of manifestations in pregnant women, including UTI, chorioamnionitis, sepsis, postnatal endometritis, and postnatal wound infection.
Intrahepatic cholestasis of pregnancy	go to our full topic on Intrahepatic cholestasis of pregnancy Intrahepatic cholestasis of pregnancy (ICP) is a disorder characterised by maternal pruritus (itch) and liver dysfunction, in the absence of other contributing liver disorders and restricted to pregnancy. Risk factors include previous or family history of ICP, cholelithiasis, and history of hepatitis C.[70][71][72][73] The condition likely occurs because of the interplay of reproductive hormones with environmental factors in genetically susceptible individuals. Maternal complications include an increased risk of gestational diabetes mellitus and pre-eclampsia, in addition to impaired glucose tolerance and dyslipidaemia; fetal complications include pre-term birth, meconium-staining of the amniotic fluid, neonatal unit admission, and, in pregnant women with bile acid concentrations of ≥100 micromol/L, intra-uterine fetal death (stillbirth).[74]
Pre-eclampsia	go to our full topic on Pre-eclampsia A disorder of pregnancy associated with new-onset hypertension (defined as a systolic blood pressure ≥140 mmHg and/or diastolic blood pressure ≥90 mmHg), which occurs most often after 20 weeks of gestation and frequently near term. Although often accompanied by new-onset proteinuria, hypertension and other signs or symptoms of pre-eclampsia may present in some women in the absence of proteinuria.[75] While the exact incidence is unknown, pre-eclampsia has been reported to occur in about 4% of all pregnancies in the US.[76] When figures include women who develop pre-eclampsia postnatally, the incidence is between 2% and 8% of all pregnancies worldwide.[77] The woman may be asymptomatic and diagnosed at a routine clinic visit, or she may present acutely with headache, upper abdominal pain, visual disturbances, breathlessness, seizures, and oliguria.
HELLP syndrome	go to our full topic on HELLP syndrome A severe form of pre-eclampsia characterised by haemolysis (H), elevated liver enzymes (EL), and low platelets (LP) in a pregnant or puerperal woman (usually within 7 days of delivery). HELLP syndrome occurs in approximately 1 to 8 per 1000 pregnancies.[78] The diagnosis of HELLP syndrome should be considered in any pregnant woman presenting in the second half of gestation or immediately post-partum with significant new-onset epigastric/right upper quadrant pain until proven otherwise. Associated with progressive and sometimes rapid maternal and fetal deterioration.
Placental abruption	go to our full topic on Placental abruption Premature separation of the normally located placenta before delivery of the fetus.[79] May be concealed or overt.[79] Associated with increased peri-natal mortality and morbidity. Also a cause of significant maternal morbidity. Placental abruption complicates about 0.3% to 1% of births.[80][81] Placental abruption may result from direct abdominal trauma, indirect trauma, or cocaine use. Risk factors include smoking, trauma, hypertensive disorders, and cocaine use.
Pre-term labour	go to our full topic on Pre-term labour Pre-term birth occurs between 24 and 37 weeks' gestation. In two-thirds of cases, it occurs following spontaneous onset of labour. Only 1% of all births occur below 32 weeks' gestation. Mortality and serious morbidity are uncommon above 32 weeks' gestation, although more subtle long-term effects, such as behavioural problems during childhood, still occur with later gestations. Premature labour has a multifactorial aetiology, and it is now viewed as a syndrome. Its causal factors can be generally categorised into maternal or fetal. Only a minority of women who present with pre-term contractions known as threatened pre-term labour progress to actual labour and delivery. The remainder of pre-term birth is due to iatrogenic delivery, most commonly because of pre-eclampsia and intrauterine growth restriction.
Breech presentation	go to our full topic on Breech presentation Breech presentation in pregnancy occurs when a baby presents with the buttocks or feet rather than the head first (cephalic presentation) and is associated with increased morbidity and mortality for both the mother and the baby.[82][83] It is common in early pregnancy and decreases with advancing gestational age, as most babies turn spontaneously to a cephalic presentation before birth.[84][85] Factors that predispose pregnancies to breech presentation include pre-term delivery, small for gestational age fetus, primiparity, congenital anomalies in the fetus, abnormal amniotic fluid volume, placental and uterine anomalies, and previous breech delivery.[86][87][88][89][90]
Rh incompatibility	go to our full topic on Rh incompatibility Rhesus (Rh) incompatibility is a condition where a Rh-negative mother carrying a Rh-positive fetus can produce antibodies against paternally-derived Rh antigens on fetal red blood cells. These antibodies can cross the placenta, and destroy fetal red blood cells. The estimated global prevalence of Rh haemolytic disease is 276/100,000 live births; in countries with well-established perinatal-neonatal care, the prevalence is approximately 2.5/100,000 live births.[91] It is a leading cause of haemolytic disease of the fetus and newborn, also known as erythroblastosis fetalis, which involves progressive fetal anaemia and, if untreated, may ultimately lead to hydrops fetalis and death.[92][93]
Premature newborn care	go to our full topic on Premature newborn care An infant born before 37 completed weeks of gestation. In addition to immediate post-birth resuscitation, efforts to reduce excessive oxygen exposure, hyperventilation, hypothermia, and hypoglycaemia must be made. Prematurity is common, accounting for 10.6% of live births globally.[94] Consultation with a neonatologist as soon as possible is recommended to reduce potential morbidity.
Postnatal depression	go to our full topic on Postnatal depression The development of a depressive illness following childbirth may form part of a bipolar or, more usually, a unipolar illness.[95] Postnatal depression is not recognised by current classification systems as a condition in its own right, but the onset of a depressive episode within 4 weeks of childbirth can be recorded via the peripartum-onset specifier in the Diagnostic and Statistical Manual of Mental Disorders, fifth edition, text revision (DSM-5-TR).[96] There is evidence to suggest that the DSM-5-TR specifier is too narrow.[97] Hence, in common usage, depressive episodes occurring within 6 to 12 months of delivery may be considered to be postnatal depression. Studies report a wide range in the prevalence of postnatal depression worldwide, ranging from 0% to 60%.[98] Strong risk factors include history of depression or anxiety, recent stressful life events, violence and abuse, poor social support, pre-term and low birth weight infants, and discontinuing psychopharmacological treatments.[99][100]

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Overview of pregnancy complications

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