mid-trimester issues and complications

see also:

• Obstetrics
• decreased fetal movements (DFM or RFM)
• fetal growth restriction (FGR / SGA / IUGR)

• most women have an uneventful 2nd trimester of pregnancy
• rate of miscarriage in second TM in low risk patients is only 0.5%
• the early stages of fetal growth restriction (FGR / SGA / IUGR) may present, or their risk mitigated for identified high risk women
• after 20 wks, their is risk of stillbirth / FDIU
• by 20wks most women should feel fetal movements and any reduction of these after 24 wks should be heeded as per decreased fetal movements (DFM or RFM) and discussed with obstetrics after a FH check has been performed
• pre-eclampsia and eclampsia is rare before 20 wks unless there are high risk factors, but may occur any time after 20 wks
• deep venous thrombosis (DVT) and pulmonary embolism (PE) are relatively common during this period as pregnancy confers a 4-5x risk
• nausea symptoms usually resolve by week 20 but about 10–20% of the patients experience symptoms beyond week 20 and some until the end of the pregnancy
• maternal insulin resistance begins in the second trimester and peaks in the third trimester
• persistent headache especially if there is neurology should be considered for a CT brain venogram to exclude cerebral dural venous sinus thrombosis (CVST)
• hyperthyroidism in the 2nd TM is relatively common and may need endocrine referral
• maternal hypertension may develop and require monitoring +/- Rx

• see also: https://en.wikipedia.org/wiki/Maternal_physiological_changes_in_pregnancy
• cardiac output has increased by 20% by 8wks pregnancy and now reaches a peak increase of around 40% at around 20-28 wks which helps offset the 25-30% fall in systemic vascular resistance due to vasodilatation which starts at 6wks. This arterial under-filling leads to lowered blood pressure and the stimulation of arterial baroreceptors, activating the RAA and the sympathetic nervous systems however there is also a relative resistance to angiotensin II
• hence patients have an increase heart rate of 10-20bpm and an increased stroke volume
• as pregnancy progresses, pressure from the gravid uterus upon the IVC restricts venous return and cardiac output by up to 25% when supine
• colloid osmotic pressure/pulmonary capillary wedge pressure gradient is reduced by about 30%, making pregnant women particularly susceptible to pulmonary oedema
• the ECG may show:
  • atrial and ventricular ectopics
  • small Q wave and inverted T in III
  • ST-segment depression and T-wave inversion in the inferior and lateral leads
  • left-axis shift of QRS
• renal plasma flow and glomerular filtration rate (GFR) both increase, compared to non-pregnant levels, by 40–65 and 50–85% and increased renal blood flow leads to an increase in renal size of 1–1.5 cm, reaching the maximal size by mid-pregnancy
• There is a significant increase in oxygen demand during normal pregnancy. This is due to a 15% increase in the metabolic rate and a 20% increased consumption of oxygen.
• There is a 40–50% increase in minute ventilation, mostly due to an increase in tidal volume, rather than in the respiratory rate, this maternal hyperventilation causes arterial pO2 to increase and arterial pCO2 to fall, with a compensatory fall in serum bicarbonate to 18–22 mmol/l causing a normal mild fully compensated respiratory alkalosis.
• the subjective feeling of breathlessness may develop and classically is present at rest or while talking and may paradoxically improve during mild activity

• usually by this stage it is clear the pregnancy is intra-uterine and thus the 1st TM considerations such as ectopic pregnancy may generally be excluded
• whilst most mild vaginal bleeding at this stage will resolve, it may be a sign of potential miscarriage due to either:
  • structural or chromosomal abnormalities
  • chorioamnionitis and cervical incompetence
  • local lesions including cervical polyps or, rarely, cervical cancer
• have a low threshold for admit under obstetric unit for further Mx
• ensure Rh isoimmunisation and Anti-D has been considered and anti-D given when indicated

• the gravid uterus in a patient with a retroverted uterus can rarely become stuck within the pelvis as it enlarges which can then cause pelvic pain, urinary issues including urinary retention and constipation
• occurs in 1 in 3000 pregnancies
• usually develops at 12-14 weeks gestation
• other causes include pelvic adhesions, uterine fibroids (leiomyomas), or other uterine or pelvic anomalies
• can be diagnosed on ultrasound
• Rx is manual repositioning of the uterus, sometimes under sedation
• if left untreated can cause uterine rupture or fetal demise

• true amniotic fluid loss is a marker of poor outcome as chorioamnionitis and miscarriage is a major risk
• assess liquor volume on ultrasound
• admit under obstetric unit for further Mx