Pregnancy Timeline: Which Test in Which Week, from the First Examination to Birth?

When a pregnancy test comes back positive, one of the first questions that comes to mind is: “So when do I go now, and for which check-up?” Pregnancy follow-up (antenatal care) is a timeline in which every week has its own question. Based on the monitoring guideline of the Sağlık Bakanlığı (Ministry of Health) in Türkiye ¹ and the contact model of the World Health Organization (WHO) ², this article brings together in one chart which test is done in which week, from the first examination to birth. Knowing the timeline in advance also makes it clearer what to expect from each check-up.

How many check-ups are there? Four visits or eight contacts?

The Antenatal Care Management Guideline of the Sağlık Bakanlığı (Ministry of Health) provides for every pregnant woman to have at least four quality visits: the first within the first 14 weeks of pregnancy, the second at weeks 18–24, the third at weeks 24–28 and the fourth at weeks 36–38 ¹. The guideline also aims for every birth to take place in hospital ¹. These four visits are a baseline; the number of visits is increased according to any risk identified, and primary care and specialist doctors work in coordination ¹.

The WHO’s 2016 model, on the other hand, recommends at least eight contacts: the first contact up to week 12, followed by weeks 20, 26, 30, 34, 36, 38 and 40 ². Contacts become more frequent as birth approaches ². The WHO recommends this number to reduce the loss of babies around the time of birth (perinatal deaths) and to improve women’s experience of care ². Both models define a minimum; the individual timeline is shaped by the risk assessment at the first visit ¹.

First examination (up to week 14): basic tests

At the first visit, the guideline calls for a full blood count, blood group (for the pregnant woman and her partner), hepatitis B (HBsAg), syphilis screening, an HIV test with informed consent, TSH for thyroid function, and a complete urine analysis with a urine culture ¹. If the mother is Rh negative and the father is Rh positive, an indirect Coombs test is done; if it is negative, it is repeated at week 28 ¹. If the blood count shows small-cell anaemia (microcytic anaemia: haemoglobin below 11 g/dL and MCV below 80 fL), iron treatment is started and checked again 2–4 weeks later; for those without iron deficiency, thalassaemia screening is recommended ¹.

At the same visit, the gestational age is established and a risk assessment is carried out ¹. If there is one major risk factor or two minor risk factors for pre-eclampsia, low-dose acetylsalicylic acid (aspirin) is recommended at weeks 12–35, provided there is no reason not to take it ¹; ideally, this protection is started before week 16 ⁸. If you are in a risk group for diabetes in pregnancy (gestational diabetes) — for example, diabetes in pregnancy in a previous pregnancy, or a history of diabetes in a first-degree relative — your blood sugar is checked at the first visit and, if needed, a glucose load test (75 g oral glucose tolerance test, OGTT) is done early ¹.

Weeks 11–14: nuchal translucency and early ultrasound

The International Society of Ultrasound in Obstetrics and Gynecology (ISUOG) lists the aims of the scan between 11 weeks 0 days and 14 weeks 0 days as follows: to confirm viability, to establish gestational age accurately using the crown–rump length (CRL), to determine the number of fetuses and, in a multiple pregnancy, the chorionicity (how the placenta is shared), to detect some major structural anomalies early and, in systems where chromosomal screening is offered, to measure the nuchal translucency (NT) ³. The Sağlık Bakanlığı (Ministry of Health) guideline also calls for the pregnant woman to be informed in these weeks about nuchal translucency and the option of the combined (double) test ¹.

The WHO also recommends one ultrasound scan before week 24; the reasons are to establish gestational age accurately, to improve the detection of anomalies and multiple pregnancies, to reduce induction of labour (starting labour with medication) for going past the due date, and to improve the woman’s experience of pregnancy ². In the guideline, alpha-fetoprotein (AFP) is measured in the mother’s blood at weeks 16–20 to screen for neural tube defects (defects in the development of the spine); if the combined test has not been done, the triple/quadruple test is also included in the same weeks ¹.

NIPT (DNA screening from the mother’s blood): for whom, and when?

The 2025 update from the US Society for Maternal-Fetal Medicine (SMFM) recommends that screening of the baby’s cell-free DNA in the mother’s blood (cfDNA; commonly known as NIPT) for trisomy 21 (Down syndrome), 18 and 13 can be offered routinely to all pregnant women, regardless of age or risk, and describes it as “the most sensitive and most specific screening test” for common abnormalities in chromosome number ⁵. The test can be done from weeks 9–10 onwards ⁵. The document was published in November 2025 with the endorsement of the American College of Obstetricians and Gynecologists (ACOG) ⁵.

The same document draws the line clearly: cfDNA is a screening test, its results are not considered diagnostic, and making decisions about the pregnancy based on this result alone is not recommended ⁵. After a positive result, genetic counselling, a detailed anatomy scan and a diagnostic test by chorionic villus sampling (CVS) or amniocentesis are recommended ⁵. Depending on the study, “no result” reports have been described in 0.03–11.1% of cases; in a recent systematic review, this rate was about 0.85% ⁵. In this situation, too, counselling, a comprehensive ultrasound scan and a diagnostic test are considered ⁵.

Weeks 18–22: detailed ultrasound

The main element of the second visit (weeks 18–24) is the detailed ultrasound scan, which the Sağlık Bakanlığı (Ministry of Health) guideline places at weeks 18–22 ¹. ISUOG recommends a mid-second-trimester scan for all pregnant women as part of routine care; the examination is carried out at around weeks 18–24, its main purpose is an organ-by-organ anatomical assessment of the fetus, and it provides a starting point for later growth monitoring ⁴. For the heart, the four-chamber, outflow tract and three-vessel views are on the standard checklist ⁴; the position of the placenta and the amniotic fluid are also assessed ¹.

It is important to have the right expectations: ISUOG writes that in experienced hands most clinically significant structural anomalies can be detected, but that detection rates vary markedly between centres and practitioners ⁴. In other words, a normal detailed scan greatly reduces the risk but does not remove it. At the same visit, the full blood count and urine test are repeated; for those with a history of preterm birth, the length of the neck of the womb (cervix) is measured by transvaginal ultrasound, and for those who have had previous surgery on the womb (uterus), the way the placenta is attached is specifically assessed ¹.

Weeks 24–28: glucose load test, Rh monitoring and blood pressure

A 50-gram glucose load test (oral glucose screening test) is recommended at weeks 24–28 for all pregnant women who are not in a high-risk group ¹. The Türk Jinekoloji ve Obstetrik Derneği (Turkish Society of Obstetrics and Gynaecology, TJOD) states clearly on its public information page that “the 50–75 grams of sugar given does not cause the baby any harm”; the test does not make you diabetic, it reveals a condition that is already there ⁷. ACOG’s 2024 update accepts both the two-step approach (50 g screening + 100 g diagnostic) and a direct 75 g OGTT ⁶.

At the third visit, the indirect Coombs test is repeated for pregnant women with Rh incompatibility; if it is negative, anti-D immunoglobulin is given ¹. In the risk group, if the glucose load test done at the first visit was normal, it is repeated in these weeks ¹. Blood pressure is measured at every visit; the guideline points out that oedema (swelling) in the hands and eyelids can also be the first sign of pre-eclampsia ¹. The decision on low-dose acetylsalicylic acid protection, however, is made at the risk assessment at the first visit ¹.

Supplements, vaccination and the final stretch: what starts in which week?

To prevent neural tube defects, the guideline provides for every woman planning a pregnancy to take 400–800 micrograms of folic acid a day, starting at least one month before pregnancy, and, in higher-risk groups, for a 4 mg dose to be started three months before and continued until week 12 ¹. If there is no anaemia, iron supplements start from week 16, and 1200 IU of vitamin D a day from week 12; the tetanus vaccine can also be given after week 12 ¹.

At the fourth visit (weeks 36–38), the baby’s presentation is assessed, a breast examination with breastfeeding in mind is carried out, the full blood count and urine test are repeated, and the birth plan and the hospital where the birth will take place are confirmed ¹. In an uncomplicated pregnancy, at least 150 minutes of moderate-intensity aerobic activity a week is recommended ⁹. The timeline is a framework; a chronic illness, a multiple pregnancy or a previous pregnancy history makes visits more frequent, and this decision is made by the doctor following the pregnancy ¹.

If you have symptoms, please see an obstetrics and gynaecology specialist.